SIST ISO 16000-3:2026

• Abstract:

  This document specifies a sampling method to determine the quantity of formaldehyde (HCHO) in the air with the range of approximately 1 µg/m3 to 1 mg/m3 in a time-weighted average (TWA) sample, for long-term (1 h to 24 h) and short-term (5 min to 60 min) sampling. This method involves the collection of compounds from air on to adsorbent cartridges coated with 2,4-dinitrophenylhydrazine (DNPH) and subsequent analysis of the hydrazones formed by high performance liquid chromatography (HPLC) with detection by ultraviolet absorption [7] [8]. ; This document can also be applied for the determination of at least 12 other aromatic as well as saturated and unsaturated aliphatic carbonyl compounds (aldehydes and ketones), with modification, such as: ; — acetaldehyde; ; — acetone; ; — benzaldehyde; ; — butyraldehyde; ; — capronaldehyde; ; — 2,5-dimethylbenzaldehyde; ; — formaldehyde; ; — isovaleraldehyde; ; — propionaldehyde; ; — m-tolualdehyde; ; — o-tolualdehyde; ; — p-tolualdehyde; ; — valeraldehyde. ; This document does not apply to longer chained or unsaturated carbonyl compounds such as acrolein. An alternative sampling method using sorbent tubes and analysis by thermal desorption using gas chromatography with mass spectrometry (GC-MS) is given in Annex A.

• Status: Not Published
• Public Enquiry End Date: 02-Aug-2026
• ICS: 13.040.20 - Ambient atmospheres
• Technical Committee: KAZ - Air quality
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 10-Sep-2026
• Due Date: 15-Nov-2026
• Ref Project: ISO 16000-3:2026 - Indoor air — Part 3: Determination of formaldehyde and other carbonyl compounds in indoor air and test chamber air — Active sampling method

• Replaces: SIST ISO 16000-3:2023 - Indoor air - Part 3: Determination of formaldehyde and other carbonyl compounds in indoor and test chamber air - Active sampling method
• Effective Date: 01-Oct-2026

Overview

SIST ISO 16000-3:2026 is an international standard developed by the Slovenian Institute for Standardization (SIST), aligned with the ISO framework, focusing on indoor air quality assessment. Titled "Indoor air - Part 3: Determination of formaldehyde and other carbonyl compounds in indoor air and test chamber air - Active sampling method," this standard specifies an active sampling method for quantifying formaldehyde and a variety of other carbonyl compounds in both indoor environments and air from test chambers. This document defines procedures for detecting formaldehyde concentrations ranging from approximately 1 µg/m³ to 1 mg/m³, using time-weighted average (TWA) sampling for both long-term (1 h to 24 h) and short-term (5 min to 60 min) intervals.

The standard utilizes the collection of contaminants on adsorbent cartridges coated with 2,4-dinitrophenylhydrazine (DNPH), followed by high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The technique is suitable for monitoring indoor air quality in residential, occupational, and controlled environments.

Key Topics

• Formaldehyde Monitoring: The method is specifically designed for the accurate determination of formaldehyde, a common indoor air pollutant with significant health impacts.
• Carbonyl Compound Detection: In addition to formaldehyde, the standard applies to at least 12 other carbonyl compounds (aromatic, saturated, and unsaturated aliphatic aldehydes/ketones), such as acetaldehyde, acetone, benzaldehyde, and valeraldehyde, among others.
• Active Sampling Method: The procedure involves the active collection of air samples on DNPH-coated cartridges, allowing for reliable and reproducible results across a wide concentration range.
• HPLC Analysis: After sampling, the standard requires HPLC with UV detection for the identification and quantification of DNPH derivatives formed from the target compounds.
• Alternative Methods: Annex A offers guidance on alternative sampling using sorbent tubes and analysis via gas chromatography-mass spectrometry (GC-MS) for certain compounds like acrolein not covered by the primary method.

Applications

• Indoor Air Quality Assessments: The standard is pivotal for environmental engineers, laboratory analysts, and industrial hygienists tasked with evaluating the presence of formaldehyde and related carbonyls in indoor environments, ensuring compliance with regulatory or occupational exposure limits.
• Building Material Testing: Used in test chambers to assess emissions from construction products, furniture, or consumer goods known to release formaldehyde and other aldehydes/ketones.
• Workplace Monitoring: Facilitates ongoing health and safety monitoring in workplaces where exposure to carbonyl compounds may occur, such as laboratories, manufacturing plants, or facilities using adhesives and coatings.
• Research and Development: Supports academic and industrial research into sources, behavior, and mitigation strategies for indoor air pollutants.
• Regulatory Compliance: Provides a validated methodology for organizations to meet legal and stakeholder requirements regarding indoor air pollutants.

Related Standards

• ISO 16000 Series: SIST ISO 16000-3:2026 is part of the ISO 16000 international series on indoor air quality, offering harmonized methods for sampling and analysis of a range of airborne contaminants.
  • ISO 16017-1 / ISO 16017-2: Broader methods for volatile organic compounds (VOC) analysis.
  • ISO 12219-1 / ISO 12219-5: Specific VOC methods for vehicle interiors.
• Other Relevant Guidelines:
  • National and regional indoor air quality guidelines may reference this standard for formaldehyde monitoring.

Adopting SIST ISO 16000-3:2026 ensures that organizations use best-practice, internationally recognized methods for indoor air sampling and analysis of formaldehyde and related compounds, delivering reliable results for health protection, compliance, and quality improvement initiatives.

International
Standard
ISO 16000-3
Fourth edition
Indoor air —
2026-09
Part 3:
Determination of formaldehyde
and other carbonyl compounds in
indoor air and test chamber air —
Active sampling method
Air intérieur —
Partie 3: Dosage du formaldéhyde et d'autres composés
carbonylés dans l'air intérieur et dans l'air des chambres d'essai
— Méthode par échantillonnage actif
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Principle . 2
5 Limitations and interferences . 2
5.1 General .2
5.2 Ozone interference .3
6 Safety measures . 4
7 Apparatus . 5
7.1 Sampling .5
7.2 Sample preparation .5
7.3 Sample analysis . .7
8 Reagents and materials . 7
9 Preparation of reagents and cartridges . 8
9.1 Purification of 2,4-dinitrophenylhydrazine .8
9.2 Preparation of DNPH formaldehyde derivative .9
9.3 Preparation of DNPH formaldehyde standards .9
9.4 Preparation of DNPH coated silica gel cartridges .9
9.4.1 General .9
9.4.2 DNPH coating solution.9
9.4.3 Coating of silica gel cartridges .10
10 Procedure .10
10.1 Sample collection . . .10
10.2 Process blanks . 12
10.3 Sample analysis . 12
10.3.1 Sample preparation . 12
10.3.2 Sample desorption . 12
10.3.3 HPLC calibration . 13
10.3.4 HPLC analysis for formaldehyde .16
10.3.5 HPLC analysis of other aldehydes and ketones .17
11 Calculations . 19
12 Performance criteria and quality assurance .20
12.1 General . 20
12.2 Standard operating procedures (SOPs) . 20
12.3 HPLC system performance . 20
12.4 Sample loss .21
12.5 Measurement plan .21
13 Precision and uncertainty .21
14 Test report .21
Annex A (informative) Determination of acrolein .23
Annex B (informative) Melting points of DNPH carbonyl derivatives .26
Annex C (informative) Precision and uncertainty .27
Bibliography .29

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement. For an explanation of the voluntary nature of standards, the meaning of ISO
specific terms and expressions related to conformity assessment, as well as information about ISO's
adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 6, Indoor air.
This fourth edition cancels and replaces the third edition (ISO 16000-3:2022), which has been technically
revised.
The main change is as follows: Annex A has been added which provides a suitable method for the
determination of acrolein.
A list of all parts in the ISO 16000 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
This document is intended to be used for characterizing indoor air following the sampling strategy specified
[1]
in ISO 16000-2 . This document applies to 14 aldehydes and ketones. Formaldehyde is the simplest
carbonyl compound, with one carbon, one oxygen and two hydrogen atoms. In its monomolecular state,
formaldehyde is a colourless, pungent and reactive gas. Formaldehyde has been used in the production of
urea-formaldehyde resins, adhesives and insulating foams. Emissions from particle (chip) board and wall
[2]
insulation are the major sources of formaldehyde in indoor air. As formaldehyde has a high toxic potential,
determining its level accurately is key for air quality.
When formaldehyde is collected by passing air through a reactive medium that converts the compound to
a derivative of lower vapour pressure is more efficiently retained by the sampler and its level can be easily
analysed.
[3] [4] [5] [6]
ISO 16017-1 , ISO 16017-2 , ISO 12219-1 and ISO 12219-5 describe analytical methods for a broader
spectrum of volatile organic compounds (VOCs) and can be used if other groups besides carbonyl compounds
are to be analyzed.
Instead of systematic International Union of Pure and Applied Chemistry (IUPAC) nomenclature, traditional
names are used in this document. Some equivalent names are:
— acetaldehyde for ethanal;
— acetone for 2-propanone;
— butyraldehyde for butanal;
— capronaldehyde for hexanal;
— formaldehyde for methanal;
— isovaleraldehyde for 3-methylbutanal;
— propionaldehyde for propanal;
— m-tolualdehyde for 3-methylbenzaldehyde;
— o-tolualdehyde for 2-methylbenzaldehyde;
— p-tolualdehyde for 4-methylbenzaldehyde;
— valeraldehyde for pentanal.
v
International Standard ISO 16000-3:2026(en)
Indoor air —
Part 3:
Determination of formaldehyde and other carbonyl
compounds in indoor air and test chamber air — Active
sampling method
1 Scope
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It
is the responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any national regulatory conditions.
This document specifies a sampling method to determine the quantity of formaldehyde (HCHO) in the
3 3
air with the range of approximately 1 µg/m to 1 mg/m in a time-weighted average (TWA) sample, for
long-term (1 h to 24 h) and short-term (5 min to 60 min) sampling. This method involves the collection
of compounds from air on to adsorbent cartridges coated with 2,4-dinitrophenylhydrazine (DNPH) and
subsequent analysis of the hydrazones formed by high performance liquid chromatography (HPLC) with
[7][8]
detection by ultraviolet absorption  .
This document can also be applied for the determination of at least 12 other aromatic as well as saturated
and unsaturated aliphatic carbonyl compounds (aldehydes and ketones), with modification, such as:
— acetaldehyde;
— acetone;
— benzaldehyde;
— butyraldehyde;
— capronaldehyde;
— 2,5-dimethylbenzaldehyde;
— formaldehyde;
— isovaleraldehyde;
— propionaldehyde;
— m-tolualdehyde;
— o-tolualdehyde;
— p-tolualdehyde;
— valeraldehyde.
This document does not apply to longer chained or unsaturated carbonyl compounds such as acrolein.
An alternative sampling method using sorbent tubes and analysis by thermal desorption using gas
chromatography with mass spectrometry (GC-MS) is given in Annex A.

2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
The method specified in this document involves the collection of compounds from air on to adsorbent
cartridges containing silica gel coated with 2,4-DNPH. The principle of the method is based on the specific
reaction of a carbonyl group with DNPH in the presence of an acid to form stable derivatives according to
the reaction shown in Figure 1. The DNPH derivatives are analysed for the parent aldehydes and ketones
[7][8]
utilizing HPLC with UV detection or diode array detection  . The detection has been extended to other
carbonyl compounds that can be determined as outlined in 10.3.5.
The preparation of sampling cartridges from commercially available chromatographic grade silica gel
cartridges by the application of acidified DNPH to each cartridge is covered in this method. If pre-coated
DNPH silica gel cartridges are available, they should be used since they are generally more uniform in
manufacture and possess lower blank levels. However, if commercial cartridges are used, demonstrate that
they meet the performance criteria of this document. An advantage of commercial cartridges is that they
are available with larger particle size silica gel – this results in a lower pressure drop across the cartridge.
These low pressure drop cartridges can be more suitable for sampling air using battery-powered personal
sampling pumps.
Carbonyl compound 2,4-DNPH DNPH derivative
(aldehyde or ketone)
Key
R alkyl group
R' aldehyde or ketone (alkyl group)
Figure 1 — Reaction of carbonyl compounds to form 2,4-dinitrophenylhydrazones
5 Limitations and interferences
5.1 General
The sampling flow rate specified in this document has been validated for sampling rates up to 1,5 l/min.
This flow rate limitation is set principally due to the high pressure drop (>8 kPa at 1,0 l/min) across the
user-prepared silica gel cartridges, which have particle sizes of 55 µm to 105 µm. These cartridges are not
generally compatible with battery-powered pumps used in personal sampling equipment (e.g. those used by
industrial hygienists).
The solid-sorbent sampling procedure is specific for sampling and analysis of formaldehyde. Interferences in
this method are caused by certain isomeric aldehydes or ketones that can be unresolved by the HPLC system
when analysing for other aldehydes and ketones. Any organic compounds that have the same retention times
and significant absorbance at 360 nm as the DNPH derivative of formaldehyde interfere. Such interferences
can often be overcome by altering the separation conditions (e.g. using alternative HPLC columns or mobile
phase compositions).
Formaldehyde contamination of the DNPH reagent is a frequently encountered problem. The DNPH shall
be purified by multiple recrystallizations in UV-grade acetonitrile (ACN). Recrystallization is accomplished,
at 40 °C to 60 °C, by slow evaporation of the solvent to maximize crystal size. Impurity levels of carbonyl
compounds in the DNPH are determined prior to use by HPLC and should be less than 0,15 µg per cartridge.
Exposure of the DNPH coated sampling cartridges to direct sunlight can produce artefacts and should be
[9]
avoided  .
Acrolein and crotonaldehyde cannot be accurately quantified by the method. Inaccurate results for these
compounds can result from the formation of multiple derivative peaks and the instability of the peak
[10]
ratios .
Nitrogen dioxide reacts with DNPH. High concentrations of NO (e.g. for gas cooking stoves) can cause
problems as the retention time of the DNPH derivative can be similar to that of the DNPH formaldehyde
[11] [12]
derivative, depending on the HPLC column and the parameters (see VDI 3862 , VDI 3862 and Reference
[13]
).
5.2 Ozone interference
If there is suspicion that abnormally high levels of ozone are present in the area being sampled (e.g. from
office copiers), special care should be taken. Ozone has been shown to interfere negatively by reacting with
[14]
both DNPH and its derivatives (hydrazones) in the cartridge  . The extent of interference depends on the
temporal variations of both the ozone and the carbonyl compounds and the duration of sampling. Significant
negative interference from ozone has been observed even at concentrations of formaldehyde and ozone
3 3 [13]
typical of clean ambient air (2 µg/m and 80 µg/m , respectively)  . The presence of ozone in the sample is
readily inferred upon analysis by the appearance of new compounds with retention times shorter than that
of the hydrazone of formaldehyde. Figure 2 shows chromatograms of samples of a formaldehyde-spiked air
stream with and without ozone.

Key
A relative absorbance
t time (min)
A with ozone
B without ozone
1 unknown substance
2 DNPH
3 formaldehyde
4 acetaldehyde
Figure 2 — Cartridge samples of formaldehyde in an air stream with and without ozone
The simplest solution to manage ozone interference is to remove the ozone before the sampled air reaches
the cartridge. This can be accomplished by the use of an ozone denuder or scrubber placed in front of the
cartridge. Both ozone denuder and scrubber cartridges are commercially available.
Use an ozone denuder of 1 m of copper tubing with an outside diameter of 0,64 cm and an inside diameter
of 0,46 cm, and with a capacity of about 200 µg/m3 h. Before using it, fill it with a saturated solution of
potassium iodide in water, allow it to stand for a few minutes (e.g. 5 min), and then drain it. Finally, dry the
denuder with a stream of clean air or nitrogen for about 1 h.Test aldehydes (formaldehyde, acetaldehyde,
propionaldehyde, benzaldehyde and p-tolualdehyde) that were dynamically spiked into an ambient sample
[15]
air stream have passed through the ozone denuder with practically no losses.
Commercial ozone scrubbers made from a cartridge filled with 300 mg to 500 mg of granular potassium
[16]
iodide are also effective for removing ozone.
6 Safety measures
2,4-dinitrophenylhydrazine is explosive in the dry state and therefore, it shall be handled with extreme
care. It is also toxic (in rats, LD = 654 mg/kg), potentially mutagenic, and irritating to the eyes and skin.
Perchloric acid at concentrations less than 68 % mass fraction is stable and non-oxidizing at room
temperature. However, it is readily dehydrated at temperatures above 160 °C and can cause explosions on
contact with alcohols, wood, cellulose and other oxidizable materials. Perchloric acid should be stored in a
cool, dry place and used only in a chemical fume hood with caution.

7 Apparatus
Usual laboratory apparatus and in particular the following.
7.1 Sampling
7.1.1 Sampling cartridge packed with silica gel and coated with DNPH in accordance with Clause 9 or as
available commercially.
The cartridge shall contain at least 350 mg of silica gel with a DNPH loading of a mass fraction of at least
0,29 %. The ratio of the silica gel bed diameter to bed length shall not exceed 1:1. The capacity of the cartridge
for formaldehyde shall be at least 75 µg and the collection efficiency shall be at least 95 % at a sampling
rate of 1,5 l/min. Sampling cartridges with very low blank levels and high performance are commercially
available.
NOTE A pressure drop through the user-prepared sample cartridge of about 19 kPa at a sampling rate of 1,5 l/min
has been observed. Some commercially available pre-coated cartridges exhibit lower pressure drops, which permit
the use of battery-operated personal sampling pumps.
7.1.2 Air sampling pump capable of accurately and precisely sampling at a flow rate of 0,1 l/min to 1,5 l/
min.
7.1.3 Flow controller, such as mass flow meters, mass flow controllers or another suitable device for
metering and setting air flow rates of 0,50 l/min to 1,20 l/min through the sample cartridge (see 10.1 for
more information on flow controller requirements).
7.1.4 Flow calibrator capable of measuring the flowrate through the cartridge accurately to within 0,1 %
of the flowrate used, such as an appropriate rotameter, soap-bubble meter or wet test meter.
7.2 Sample preparation
7.2.1 Cartridge containers, e.g. borosilicate glass culture tubes (20 mm × 125 mm) with polypropylene
screw caps.
7.2.2 Non-absorbent gloves.
Polythene gloves have been found suitable.
7.2.3 Transportation containers, such as friction-top metal cans (e.g. with a volume of 4 l) or other
suitable containers, with polyethylene air-bubble packing or other suitable padding, to hold and cushion the
sealed cartridge containers.
NOTE The heat sealable foil-lined plastic pouch of the type included with some commercial pre-coated DNPH
cartridges can be used for storing a DNPH-coated cartridge after sampling, if appropriate.
7.2.4 Support for coating cartridges.
A suitable inert support for holding drying cartridges shall be used, e.g. a syringe rack (see Figure 3).
7.2.5 Cartridge drying manifold such as a support with gas connectors and with multiple standard male
syringe connectors (see Figure 3).
The apparatus specified in 7.2.4 and 7.2.5 is needed only if the user chooses to make their own DNPH-coated
cartridges.
a) Rack for coating cartridges
b) Rack for drying DNPH coated cartridges
Key
1 10 ml glass syringe
2 test tube rack
3 cartridges
4 waste beaker
5 N gas stream
6 syringe fitting
7 waste vial
Figure 3 — Syringe rack for coating and drying sample cartridges

7.3 Sample analysis
7.3.1 HPLC system, consisting of
a) a mobile phase reservoir with an outgassing device (e.g. membrane under reduced pressure);
b) a high-pressure pump;
c) an injection valve (automatic sampler with a 25 µl or other convenient loop volume);
d) a C-18 reverse phase (RP) column (e.g. 25 cm, 4,6 mm inside diameter, 5 µm particle size);
e) a UV detector or diode array detector operating at 360 nm;
f) a data recording system.
The DNPH-formaldehyde derivative is determined using isocratic reverse phase HPLC, equipped with
an ultraviolet (UV) absorption detector operated at 360 nm. A blank cartridge is likewise desorbed and
analysed. Formaldehyde and other carbonyl compounds in the sample are identified and quantified by
comparison of their retention times and peak heights or peak areas with those of standard solutions.
NOTE 1 Most commercial HPLC analytical systems are adequate for this application.
NOTE 2 A column oven can be used to assure constant column operating temperature and improve reproducibility.
7.3.2 Syringes and pipettes.
7.3.2.1 HPLC injection syringes with capacity of at least four times the loop volume (see 7.3.1).
7.3.2.2 Syringes with a volume of 10 ml, to prepare DNPH-coated cartridges (polypropylene syringes are
adequate).
7.3.2.3 Syringe fittings and plugs, to connect cartridges to the sampling system and to cap prepared
cartridges.
7.3.2.4 Pipettes positive-displacement, repetitive-dispersing type, with capacities in the range of 0 ml to
[17]
10 ml (see ISO 8655-2 ).
8 Reagents and materials
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade, e.g. best
quality grade, grade for chemical analysis or grade for HPLC analysis, and distilled or demineralized water
or water of equivalent purity.
8.1 2,4-dinitrophenylhydrazine, recrystallized at least twice with UV grade acetonitrile before use.
8.2 Acetonitrile, UV grade (each batch of solvent should be tested before use).
8.3 Perchloric acid, with a mass fraction of 60 %, ρ = 1,51 kg/l, reagent grade (best source).
8.4 Hydrochloric acid, with a mass fraction of 36,5 % to 38 %, ρ = 1,19 kg/l, reagent grade (best source).
8.5 Hydrochloric acid of 2 mol/l, reagent grade (best source).
8.6 Formaldehyde solution, with a mass fraction of 37 %, reagent grade (best source).

8.7 Aldehydes and ketones, high purity, used for preparation of DNPH derivative standards (optional).
8.8 Ethanol or methanol, HPLC grade.
8.9 Nitrogen, high purity grade (best source).
8.10 Charcoal, granular (best source).
8.11 Helium, high purity grade (best source).
9 Preparation of reagents and cartridges
9.1 Purification of 2,4-dinitrophenylhydrazine
Formaldehyde contamination of the DNPH reagent is a frequently encountered problem. The DNPH (8.1) shall
be purified by multiple recrystallizations in UV grade acetonitrile (8.2). Recrystallization is accomplished,
at 40 °C to 60 °C, by slow evaporation of the solvent to maximize crystal size. Impurity levels of carbonyl
compounds in the DNPH are determined prior to use by HPLC and should be less than 0,15 µg per cartridge
and per individual compound.
Prepare a supersaturated solution of DNPH by boiling excess DNPH in 200 ml of acetonitrile for approximately
1 h. After 1 h, remove and transfer the supernatant to a covered beaker on a hot plate and allow gradual
cooling to 40 °C to 60 °C. Maintain the solution at this temperature (40 °C) until a solvent with a volume
fraction of 95 % has evaporated. Decant the solution to waste and rinse the remaining crystals twice with
three times their apparent volume of acetonitrile. Transfer the crystals to another clean beaker, add 200 ml
of acetonitrile, heat to boiling, and again let crystals grow slowly at 40 °C to 60 °C until a solvent with a
volume fraction of 95 % has evaporated. Repeat this rinsing process.
Take an aliquot of the second rinse, dilute 10 times with acetonitrile, acidify with 1 ml of 3,8 mol/l perchloric
acid (8.3) per 100 ml of DNPH solution and analyse by HPLC, in accordance with 10.3.4.
WARNING — Carry out this procedure under a properly ventilated hood and behind an explosion
shield.
NOTE An acid is necessary to catalyse the reaction of carbonyl compounds with DNPH. Most strong inorganic acids
such as hydrochloric, sulfuric, phosphoric or perchloric acids can be used satisfactorily. In rare cases, hydrochloric
and sulfuric acids cause problems.
An acceptable impurity level is less than 0,025 µg/ml of formaldehyde hydrazine in recrystallized DNPH
reagent or DNPH with a mass fraction of 0,02 %.
If the impurity level is not acceptable for the intended sampling application, repeat recrystallization.
Transfer the purified crystals to an all-glass reagent bottle, add 200 ml of acetonitrile, stopper, shake gently
and allow to stand overnight. Analyse the supernatant by HPLC in accordance with 10.3.4. If the impurity
level surpasses the acceptable limit, pipette off the solution to waste, then add 25 ml of acetonitrile to the
purified crystals. Repeat rinsing with 20 ml portions of acetonitrile until an acceptable low impurity level in
the supernatant is confirmed by HPLC analysis.
If the impurity level is acceptable, add another 25 ml of acetonitrile, stopper, shake the reagent bottle and
then set aside. The saturated solution above the purified crystals is the stock DNPH reagent. Maintain only a
minimum volume of saturated solution adequate for day-to-day operation. This minimizes waste of purified
reagent, should it be necessary to re-rinse the crystals to decrease the level of impurity for applications
requiring more stringent purity specifications. Use clean pipettes when removing saturated DNPH stock
solution for any analytical applications. Do not pour the stock solution from the reagent bottle.

9.2 Preparation of DNPH formaldehyde derivative
To a portion of the recrystallized DNPH (9.1), add a sufficient quantity of HCl of 2 mol/l (8.5) to obtain
an approximately saturated solution. Add formaldehyde (8.6) that is in molar excess of the DNPH to this
solution. Filter the DNPH-formaldehyde precipitate, wash it with HCl of 2 mol/l and water, and then allow it
to dry in air.
Check the purity of the DNPH-formaldehyde derivative by melting point determination (165 °C to 166 °C) or
HPLC analysis. If the impurity level is not acceptable, recrystallize the derivative in ethanol (8.8). Repeat the
purity check and recrystallize as necessary until an acceptable level of purity (e.g. mass fraction of 99 %) is
achieved.
The DNPH-formaldehyde derivative should be stored under refrigeration (4 °C) and protected from light. It
should be stable for at least six months. Storage under nitrogen (8.9) or argon further prolongs the lifetime
of the derivative.
Melting points of DNPH derivatives of several carbonyl compounds are given in Annex B.
DNPH derivatives of formaldehyde and other carbonyls (8.7) suitable for use as standards are commercially
available both in the form of pure crystals and as individual or mixed stock solutions in acetonitrile.
9.3 Preparation of DNPH formaldehyde standards
Prepare a standard stock solution of the DNPH-formaldehyde derivative by dissolving accurately weighed
amounts in acetonitrile (8.2). Prepare a working calibration standard mix from the standard stock solution.
The concentration of the DNPH-formaldehyde derivative in the standard mix solutions should be adjusted to
reflect the range of concentrations expected in real samples.
Individual stock solutions of approximately 100 mg/l can be prepared by dissolving 10 mg of the solid
derivative in 100 ml of acetonitrile. The individual solution is used to prepare calibration standards
containing the derivative of interest at concentrations of 0,5 µg/ml to 20 µg/ml, that spans the concentration
of interest.
Store all standard solutions in tightly capped containers in a refrigerator and protected from light. Allow
them to equilibrate to room temperature before use. They should be replaced after four weeks.
9.4 Preparation of DNPH coated silica gel cartridges
9.4.1 General
This procedure shall be performed in an atmosphere with a very low aldehyde background concentration.
All glassware and plasticware shall be thoroughly cleaned and rinsed with deionized water and aldehyde-
free acetonitrile (8.2). Contact of reagents with laboratory air shall be minimized. Gloves shall be worn when
handling the cartridges.
9.4.2 DNPH coating solution
Pipette 30 ml of saturated DNPH stock solution into a 1 000 ml volumetric flask, then add 500 ml
acetonitrile (8.2). Acidify with 1,0 ml of concentrated HCl (8.5).
The atmosphere above the acidified solution should preferably be filtered through a DNPH-coated silica
gel cartridge, to minimize contamination from laboratory air. Shake solution, then make up to volume with
acetonitrile. Stopper the flask, invert and shake several times until the solution is homogeneous. Transfer
the acidified solution to a reagent bottle equipped with a positive-displacement dispenser of capacity in the
0 ml to 10 ml range.
Prime the dispenser and slowly dispense 10 ml to 20 ml to waste. Dispense an aliquot solution to a sample
vial and check the impurity level of the acidified solution by HPLC in accordance with 10.3.4. The impurity
level of formaldehyde should be <0,025 µg/ml.

9.4.3 Coating of silica gel cartridges
Open the cartridge package, connect the short end of the silica gel cartridge (7.1.1) to a 10 ml syringe,
and place it in the syringe rack (7.2.4) as illustrated in Figure 3. Using a positive-displacement repetitive
pipette (7.3.2.4), add 10 ml of acetonitrile (8.2) to each of the syringes. Let liquid drain to waste by gravity.
Remove any air bubbles that are trapped between the syringe and the silica cartridge by displacing them
with the acetonitrile in the syringe.
Set the repetitive dispenser, containing the acidified DNPH coating solution, to dispense 7 ml into the
cartridges. Once the effluent flow at the outlet of the cartridge has stopped, dispense 7 ml of the coating
reagent into each of the syringes. Let the coating reagent drain by gravity through the cartridge until flow at
the other end of the cartridge stops. Wipe away the excess liquid at the outlet of each of the cartridges with
clean tissue paper.
Assemble a drying manifold as shown in Figure 3 b). This contains a previously prepared DNPH-coated
cartridge at each of the exit ports (e.g. scrubber or “guard cartridges”). These “guard cartridges” serve to
remove traces of formaldehyde that can be present in the nitrogen (8.9) gas supply. They can be prepared
by drying a few of the newly coated cartridges according to the following instructions and testing these to
ensure the purity of the rest.
— Insert cartridge connectors [flared at both ends, 0,64 cm × 2,5 cm outside diameter polytetrafluoroethylene
(PTFE) tubing with the inside diameter slightly smaller than the outside diameter of the cartridge port]
on to the long end of the scrubber cartridges.
— Remove the cartridges from the syringes and connect the short ends of the cartridges to the open end of
the cartridge connectors already attached to the scrubber cartridges.
— Pass nitrogen (8.9) through each of the cartridges at about 300 ml/min to 400 ml/min. Rinse the exterior
surfaces and outlet end of the cartridges with acetonitrile using a Pasteur pipette. After 15 min, stop the
flow of nitrogen, wipe the cartridge exterior free of acetonitrile and remove the dried cartridges. Plug
both ends of the coated cartridge with standard polypropylene male syringe plugs and place the plugged
cartridge in a borosilicate glass culture tube with polypropylene screw caps (7.2.1).
— Put a serial number and a lot number label on each of the individual cartridge glass storage containers
and refrigerate the prepared lot until use.
Sampling cartridges have been found to be stable for at least six months when stored at 4 °C in the absence
of light.
10 Procedure
10.1 Sample collection
Assemble the sampling system and ensure that the pump (7.1.2) is capable of constant flow rate throughout
the sampling period. The sampling cartridges (7.1.1) can be safely used for sampling air when the
temperature is above 10 °C. If required, add an ozone denuder or scrubber (see 5.2).
Before sample collection, check the system for leaks. Plug the inlet of the cartridge so no flow is indicated at
the outlet end of the pump. The flow meter should not indicate any air flow through the sampling apparatus.
For unattended or extended sampling periods, a mass flow controller (7.1.3) or, as appropriate, a compensated
personal sampling pump should be used to maintain constant flow. The flow controller should be set at least
20 % below the fixed maximum air flow rate through the cartridge.
NOTE 1 The silica gel is held in the cartridge between two fine-porosity filter frits. Air flow during sampling can
change as airborne particulates deposit on the front frit. The flow change can be significant when sampling particulate-
laden atmospheres.
Install the entire assembly (including a “dummy” sampling cartridge) and check the flow rate at a value
near the desired rate. Flow rates of 0,5 l/min to 1,2 l/min shall be employed. The total number of moles of

carbonyl in the volume of air sampled shall not exceed that of the DNPH (2 mg or 0,01 mol/cartridge; 1 mg to
2 mg/cartridge for commercially available pre-coated cartridges). In general, a safe estimate of the sample
size should be lower than 75 % of the DNPH mass loading of the cartridge [100 µg to 200 µg as HCHO, with
respect to interferences to be taken into account (see Clause 5)]. Generally, calibration can be accomplished
using a soap-bubble flow meter or calibrated wet test meter (7.1.4) connected to the flow exit, assuming the
system is leak tight.
[18]
NOTE 2 ISO 13137 specifies an appropriate calibration scheme that does not require a sealed flow system
downstream of the pump.
Measure and record the sampling flow rate at the beginning and end of the sampling period to determine
sample volume. If the sampling period exceeds 2 h, the flow rate should be measured at intermediate points
during the sampling period. Include a rotameter to allow observation of the flow rate without interruption
of the sampling process. Alternatively, a sampling pump which directly measures and continuously records
the flow rate can be used.
Before sampling, remove the cartridge container from the friction-top metal can or other suitable container.
Let the cartridge warm to a temperature above 10 °C in the glass tube before connecting it to the sampling
train.
If a commercial pre-coated DNPH cartridge is used, let the cartridge warm to a temperature above 10 °C
before connecting to the sampling train.
Using gloves (7.2.2), remove the syringe plugs and connect the cartridge to the sampling system with
a syringe adapter fitting. Connect the cartridge to the sampling train so that the short end becomes the
sample inlet.
With commercial pre-coated DNPH cartridges, follow the manufacturer's instructions.
Turn the sampler on and adjust the flow to the desired rate. A typical flow rate through one cartridge is 1,0 l/
min and 0,8 l/min for two cartridges in tandem. Operate the sampler for the desired period, with periodic
recording of the sampling variables.
If the ambient air temperature during sampling is below 10 °C, the sampling cartridge should be kept in a
warmer environment. No significant effects of relative humidity have been observed for sampling under
various weather conditions — cold, wet and dry winter months as well as hot and humid summer months.
At the end of the sampling period, check the flow rate just before stopping the flow. If the flow rates at the
beginning and end of the sampling period differ by more than 10 %, the sample should be marked as suspect.
If there is a need to convert the concentrations to standard conditions (temperature and pressure) by
calculation, temperature and pressure have to be measured during sampling.
Immediately after sampling, remove the cartridge (using gloves) from the sampling system, cap with the
original end plugs and place it back in the original labelled container. Seal with PTFE tape and place in a
friction-top can (7.2.3) containing 2 cm to 5 cm depth of granular charcoal (8.10) or in another suitable
container with appropriate padding. If appropriate, a heat-sealable foil-lined plastic pouch may be used for
storing the exposed cartridge. Refrigerate the exposed sample cartridge until analysis. The refrigeration
period prior to analysis should not exceed 30 days.
If samples are to be transported to a central laboratory for analysis, the duration of the non-refrigerated
period should be kept to a minimum, preferably less t
...

SLOVENSKI STANDARD
oSIST ISO/FDIS 16000-3:2026
01-julij-2026
Notranji zrak - 3. del: Določanje formaldehida in drugih karbonilnih spojin v
notranjem zraku in zraku v preskusnih komorah - Metoda aktivnega vzorčenja
Indoor air - Part 3: Determination of formaldehyde and other carbonyl compounds in
indoor air and test chamber air - Active sampling method
Air intérieur - Partie 3: Dosage du formaldéhyde et d'autres composés carbonylés dans
l'air intérieur et dans l'air des chambres d'essai - Méthode par échantillonnage actif
Ta slovenski standard je istoveten z: ISO/FDIS 16000-3
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
oSIST ISO/FDIS 16000-3:2026 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST ISO/FDIS 16000-3:2026
oSIST ISO/FDIS 16000-3:2026
FINAL DRAFT
International
Standard
ISO/FDIS 16000-3
ISO/TC 146/SC 6
Indoor air —
Secretariat: DIN
Part 3:
Voting begins on:
2026-06-10
Determination of formaldehyde
and other carbonyl compounds in
Voting terminates on:
2026-08-05
indoor air and test chamber air —
Active sampling method
Air intérieur —
Partie 3: Dosage du formaldéhyde et d'autres composés
carbonylés dans l'air intérieur et dans l'air des chambres d'essai
— Méthode par échantillonnage actif
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 16000-3:2026(en) © ISO 2026

oSIST ISO/FDIS 16000-3:2026
FINAL DRAFT
ISO/FDIS 16000-3:2026(en)
International
Standard
ISO/FDIS 16000-3
ISO/TC 146/SC 6
Indoor air —
Secretariat: DIN
Part 3:
Voting begins on:
Determination of formaldehyde
and other carbonyl compounds in
Voting terminates on:
indoor air and test chamber air —
Active sampling method
Air intérieur —
Partie 3: Dosage du formaldéhyde et d'autres composés
carbonylés dans l'air intérieur et dans l'air des chambres d'essai
— Méthode par échantillonnage actif
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
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Published in Switzerland Reference number
ISO/FDIS 16000-3:2026(en) © ISO 2026

ii
oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Principle . 2
5 Limitations and interferences . 2
5.1 General .2
5.2 Ozone interference .3
6 Safety measures . 4
7 Apparatus . 5
7.1 Sampling .5
7.2 Sample preparation .5
7.3 Sample analysis . .6
8 Reagents and materials . 7
9 Preparation of reagents and cartridges . 7
9.1 Purification of 2,4-dinitrophenylhydrazine .7
9.2 Preparation of DNPH formaldehyde derivative .8
9.3 Preparation of DNPH formaldehyde standards .8
9.4 Preparation of DNPH coated silica gel cartridges .9
9.4.1 General .9
9.4.2 DNPH coating solution.9
9.4.3 Coating of silica gel cartridges .9
10 Procedure .10
10.1 Sample collection . . .10
10.2 Process blanks .11
10.3 Sample analysis . 12
10.3.1 Sample preparation . 12
10.3.2 Sample desorption . 12
10.3.3 HPLC calibration . 12
10.3.4 HPLC analysis for formaldehyde . 15
10.3.5 HPLC analysis of other aldehydes and ketones .17
11 Calculations . 19
12 Performance criteria and quality assurance .20
12.1 General . 20
12.2 Standard operating procedures (SOPs) . 20
12.3 HPLC system performance . 20
12.4 Sample loss .21
12.5 Measurement plan .21
13 Precision and uncertainty .21
14 Test report .21
Annex A (informative) Determination of acrolein .23
Annex B (informative) Melting points of DNPH carbonyl derivatives .26
Annex C (informative) Precision and uncertainty .27
Bibliography .29

iii
oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement. For an explanation of the voluntary nature of standards, the meaning of ISO
specific terms and expressions related to conformity assessment, as well as information about ISO's
adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 6, Indoor air.
This fourth edition cancels and replaces the third edition (ISO 16000-3:2022), which has been technically
revised.
The main change is as follows: Annex A has been added which provides a suitable method for the
determination of acrolein.
A list of all parts in the ISO 16000 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
Introduction
This document is intended to be used for characterizing indoor air following the sampling strategy specified
[1]
in ISO 16000-2 . This document applies to 14 aldehydes and ketones. Formaldehyde is the simplest
carbonyl compound, with one carbon, one oxygen and two hydrogen atoms. In its monomolecular state,
formaldehyde is a colourless, pungent and reactive gas. Formaldehyde has been used in the production of
urea-formaldehyde resins, adhesives and insulating foams. Emissions from particle (chip) board and wall
[2]
insulation are the major sources of formaldehyde in indoor air. As formaldehyde has a high toxic potential ,
determining its level accurately is key for air quality.
When formaldehyde is collected by passing air through a reactive medium that converts the compound to
a derivative of lower vapour pressure is more efficiently retained by the sampler and its level can be easily
analysed.
[3] [4] [5] [6]
ISO 16017-1 , ISO 16017-2 , ISO 12219-1 and ISO 12219-5 describe analytical methods for a broader
spectrum of volatile organic compounds (VOC) and can be used if other groups besides carbonyl compounds
are to be analyzed.
Instead of systematic IUPAC nomenclature, traditional names are used in this document. Some equivalent
names are:
— acetaldehyde for ethanal;
— acetone for 2-propanone;
— butyraldehyde for butanal;
— capronaldehyde for hexanal;
— formaldehyde for methanal;
— isovaleraldehyde for 3-methylbutanal;
— propionaldehyde for propanal;
— m-tolualdehyde for 3-methylbenzaldehyde;
— o-tolualdehyde for 2-methylbenzaldehyde;
— p-tolualdehyde for 4-methylbenzaldehyde;
— valeraldehyde for pentanal.
v
oSIST ISO/FDIS 16000-3:2026
oSIST ISO/FDIS 16000-3:2026
FINAL DRAFT International Standard ISO/FDIS 16000-3:2026(en)
Indoor air —
Part 3:
Determination of formaldehyde and other carbonyl
compounds in indoor air and test chamber air — Active
sampling method
Warning — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It
is the responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any national regulatory conditions.
1 Scope
This document specifies a sampling method to determine the quantity of formaldehyde (HCHO) in the
3 3
air with the range of approximately 1 µg/m to 1 mg/m in a time-weighted average (TWA) sample, for
long-term (1 h to 24 h) and short-term (5 min to 60 min) sampling. This method involves the collection
of compounds from air on to adsorbent cartridges coated with 2,4-dinitrophenylhydrazine (DNPH) and
subsequent analysis of the hydrazones formed by high performance liquid chromatography (HPLC) with
[7][8]
detection by ultraviolet absorption .
This document can also be applied for the determination of at least 12 other aromatic as well as saturated
and unsaturated aliphatic carbonyl compounds (aldehydes and ketones), with modification, such as:
— acetaldehyde;
— acetone;
— benzaldehyde;
— butyraldehyde;
— capronaldehyde;
— 2,5-dimethylbenzaldehyde;
— formaldehyde;
— isovaleraldehyde;
— propionaldehyde;
— m-tolualdehyde;
— o-tolualdehyde;
— p-tolualdehyde;
— valeraldehyde.
This document does not apply to longer chained or unsaturated carbonyl compounds such as acrolein.
An alternative sampling method using sorbent tubes and analysis by thermal desorption using gas
chromatography with mass spectrometry (GC-MS) is given in Annex A.

oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
The method specified in this document involves the collection of compounds from air on to adsorbent
cartridges containing silica gel coated with 2,4-dinitrophenylhydrazine (DNPH). The principle of the
method is based on the specific reaction of a carbonyl group with DNPH in the presence of an acid to form
stable derivatives according to the reaction shown in Figure 1. The DNPH derivatives are analysed for the
parent aldehydes and ketones utilizing high performance liquid chromatography (HPLC) with UV detection
[7][8]
or diode array detection . The detection has been extended to other carbonyl compounds that can be
determined as outlined in 10.3.5.
The preparation of sampling cartridges from commercially available chromatographic grade silica gel
cartridges by the application of acidified DNPH to each cartridge is covered in this method. If pre-coated
DNPH silica gel cartridges are available, they should be used since they are generally more uniform in
manufacture and possess lower blank levels. However, if commercial cartridges are used, demonstrate that
they meet the performance criteria of this document. An advantage of commercial cartridges is that they
are available with larger particle size silica gel – this results in a lower pressure drop across the cartridge.
These low pressure drop cartridges can be more suitable for sampling air using battery-powered personal
sampling pumps.
Carbonyl compound 2,4-Dinitrophenylhydrazine DNPH deriative
(aldehyde or ketone) (DNPH)
Key
R alkyl group
R' H aromatic group
Figure 1 — Reaction of carbonyl compounds to form 2,4-dinitrophenylhydrazones
5 Limitations and interferences
5.1 General
The sampling flow rate specified in this document has been validated for sampling rates up to 1,5 l/min.
This flow rate limitation is set principally due to the high pressure drop (>8 kPa at 1,0 l/min) across the
user-prepared silica gel cartridges, which have particle sizes of 55 µm to 105 µm. These cartridges are not
generally compatible with battery-powered pumps used in personal sampling equipment (e.g. those used by
industrial hygienists).
oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
The solid-sorbent sampling procedure is specific for sampling and analysis of formaldehyde. Interferences in
this method are caused by certain isomeric aldehydes or ketones that can be unresolved by the HPLC system
when analysing for other aldehydes and ketones. Any organic compounds that have the same retention times
and significant absorbance at 360 nm as the DNPH derivative of formaldehyde interfere. Such interferences
can often be overcome by altering the separation conditions (e.g. using alternative HPLC columns or mobile
phase compositions).
Formaldehyde contamination of the DNPH reagent is a frequently encountered problem. The DNPH shall
be purified by multiple recrystallizations in UV-grade acetonitrile (ACN). Recrystallization is accomplished,
at 40 °C to 60 °C, by slow evaporation of the solvent to maximize crystal size. Impurity levels of carbonyl
compounds in the DNPH are determined prior to use by HPLC and should be less than 0,15 µg per cartridge.
Exposure of the DNPH coated sampling cartridges to direct sunlight can produce artefacts and should be
[9]
avoided .
Acrolein and crotonaldehyde cannot be accurately quantified by the method. Inaccurate results for these
compounds can result from the formation of multiple derivative peaks and the instability of the peak
[10]
ratios .
Nitrogen dioxide reacts with DNPH. High concentrations of NO (e.g. for gas cooking stoves) can cause
problems as the retention time of the DNPH derivative can be similar to that of the DNPH formaldehyde
[11] [12]
derivative, depending on the HPLC column and the parameters (see VDI 3862 , VDI 3862 and Reference
[13]
).
5.2 Ozone interference
If there is suspicion that abnormally high levels of ozone are present in the area being sampled (e.g. from
office copiers), special care should be taken. Ozone has been shown to interfere negatively by reacting with
[14]
both DNPH and its derivatives (hydrazones) in the cartridge . The extent of interference depends on the
temporal variations of both the ozone and the carbonyl compounds and the duration of sampling. Significant
negative interference from ozone has been observed even at concentrations of formaldehyde and ozone
3 3 [13]
typical of clean ambient air (2 µg/m and 80 µg/m , respectively) . The presence of ozone in the sample is
readily inferred upon analysis by the appearance of new compounds with retention times shorter than that
of the hydrazone of formaldehyde. Figure 2 shows chromatograms of samples of a formaldehyde-spiked air
stream with and without ozone.

oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
Key
A relative absorbance
t time (min)
A with ozone
B without ozone
1 unknown substance
2 DNPH
3 formaldehyde
4 acetaldehyde
Figure 2 — Cartridge samples of formaldehyde in an air stream with and without ozone
The simplest solution to manage ozone interference is to remove the ozone before the sampled air reaches
the cartridge. This can be accomplished by the use of an ozone denuder or scrubber placed in front of the
cartridge. Both ozone denuder and scrubber cartridges are commercially available.
Use an ozone denuder of 1 m of copper tubing with an outside diameter of 0,64 cm and an inside diameter
of 0,46 cm, and with a capacity of about 200 µg/m3 h. Before using it, fill it with a saturated solution of
potassium iodide in water, allow it to stand for a few minutes (e.g. 5 min), and then drain it. Finally, dry the
denuder with a stream of clean air or nitrogen for about 1 h.Test aldehydes (formaldehyde, acetaldehyde,
propionaldehyde, benzaldehyde and p-tolualdehyde) that were dynamically spiked into an ambient sample
[15]
air stream have passed through the ozone denuder with practically no losses .
Commercial ozone scrubbers made from a cartridge filled with 300 mg to 500 mg of granular potassium
[16]
iodide are also effective for removing ozone .
6 Safety measures
2,4-dinitrophenylhydrazine is explosive in the dry state and therefore, it shall be handled with extreme
care. It is also toxic (in rats, LD = 654 mg/kg), potentially mutagenic, and irritating to the eyes and skin.
Perchloric acid at concentrations less than 68 % mass fraction is stable and non-oxidizing at room
temperature. However, it is readily dehydrated at temperatures above 160 °C and can cause explosions on
contact with alcohols, wood, cellulose and other oxidizable materials. Perchloric acid should be stored in a
cool, dry place and used only in a chemical fume hood with caution.

oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
7 Apparatus
Usual laboratory apparatus and in particular the following.
7.1 Sampling
7.1.1 Sampling cartridge packed with silica gel and coated with DNPH in accordance with Clause 9 or as
available commercially.
The cartridge shall contain at least 350 mg of silica gel with a DNPH loading of a mass fraction of at least
0,29 %. The ratio of the silica gel bed diameter to bed length shall not exceed 1:1. The capacity of the cartridge
for formaldehyde shall be at least 75 µg and the collection efficiency shall be at least 95 % at a sampling
rate of 1,5 l/min. Sampling cartridges with very low blank levels and high performance are commercially
available.
NOTE A pressure drop through the user-prepared sample cartridge of about 19 kPa at a sampling rate of 1,5 l/min
has been observed. Some commercially available pre-coated cartridges exhibit lower pressure drops, which permit
the use of battery-operated personal sampling pumps.
7.1.2 Air sampling pump capable of accurately and precisely sampling at a flow rate of 0,1 l/min to 1,5 l/
min.
7.1.3 Flow controller, such as mass flow meters, mass flow controllers or another suitable device for
metering and setting air flow rates of 0,50 l/min to 1,20 l/min through the sample cartridge (see 10.1 for
more information on flow controller requirements).
7.1.4 Flow calibrator capable of measuring the flowrate through the cartridge accurately to within 0,1 %
of the flowrate used, such as an appropriate rotameter, soap-bubble meter or wet test meter.
7.2 Sample preparation
7.2.1 Cartridge containers, e.g. borosilicate glass culture tubes (20 mm × 125 mm) with polypropylene
screw caps.
7.2.2 Non-absorbent gloves.
Polythene gloves have been found suitable.
7.2.3 Transportation containers, such as friction-top metal cans (e.g. with a volume of 4 l) or other
suitable containers, with polyethylene air-bubble packing or other suitable padding, to hold and cushion the
sealed cartridge containers.
NOTE The heat sealable foil-lined plastic pouch of the type included with some commercial pre-coated DNPH
cartridges can be used for storing a DNPH-coated cartridge after sampling, if appropriate.
7.2.4 Support for coating cartridges.
A suitable inert support for holding drying cartridges shall be used, e.g. a syringe rack (see Figure 3).
7.2.5 Cartridge drying manifold such as a support with gas connectors and with multiple standard male
syringe connectors (see Figure 3).
The apparatus specified in 7.2.4 and 7.2.5 is needed only if the user chooses to make their own DNPH-coated
cartridges.
oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
a) Rack for coating cartridges
b) Rack for drying DNPH coated cartridges
Key
1 10 ml glass syringes
2 test tube rack
3 cartridges
4 waste beakers
5 N gas stream
6 syringe fitting
7 waste vials
Figure 3 — Syringe rack for coating and drying sample cartridges
7.3 Sample analysis
7.3.1 HPLC system, consisting of
a) a mobile phase reservoir with an outgassing device (e.g. membrane under reduced pressure);
b) a high-pressure pump;
c) an injection valve (automatic sampler with a 25 µl or other convenient loop volume);
d) a C-18 reverse phase (RP) column (e.g. 25 cm, 4,6 mm inside diameter, 5 µm particle size);
e) a UV detector or diode array detector operating at 360 nm;
f) a data recording system.
The DNPH-formaldehyde derivative is determined using isocratic reverse phase HPLC, equipped with
an ultraviolet (UV) absorption detector operated at 360 nm. A blank cartridge is likewise desorbed and
analysed. Formaldehyde and other carbonyl compounds in the sample are identified and quantified by
comparison of their retention times and peak heights or peak areas with those of standard solutions.
NOTE 1 Most commercial HPLC analytical systems are adequate for this application.
NOTE 2 A column oven can be used to assure constant column operating temperature and improve reproducibility.

oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
7.3.2 Syringes and pipettes.
7.3.2.1 HPLC injection syringes with capacity of at least four times the loop volume (see 7.3.1).
7.3.2.2 Syringes with a volume of 10 ml, to prepare DNPH-coated cartridges (polypropylene syringes are
adequate).
7.3.2.3 Syringe fittings and plugs, to connect cartridges to the sampling system and to cap prepared
cartridges.
7.3.2.4 Pipettes positive-displacement, repetitive-dispersing type, with capacities in the range of 0 ml to
[17]
10 ml (see ISO 8655-2 ).
8 Reagents and materials
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade, e.g. best
quality grade, grade for chemical analysis or grade for HPLC analysis, and distilled or demineralized water
or water of equivalent purity.
8.1 2,4-dinitrophenylhydrazine, recrystallized at least twice with UV grade acetonitrile before use.
8.2 Acetonitrile, UV grade (each batch of solvent should be tested before use).
8.3 Perchloric acid, with a mass fraction of 60 %, ρ = 1,51 kg/l, reagent grade (best source).
8.4 Hydrochloric acid, with a mass fraction of 36,5 % to 38 %, ρ = 1,19 kg/l, reagent grade (best source).
8.5 Hydrochloric acid of 2 mol/l, reagent grade (best source).
8.6 Formaldehyde solution, with a mass fraction of 37 %, reagent grade (best source).
8.7 Aldehydes and ketones, high purity, used for preparation of DNPH derivative standards (optional).
8.8 Ethanol or methanol, HPLC grade.
8.9 Nitrogen, high purity grade (best source).
8.10 Charcoal, granular (best source).
8.11 Helium, high purity grade (best source).
9 Preparation of reagents and cartridges
9.1 Purification of 2,4-dinitrophenylhydrazine
Formaldehyde contamination of the DNPH reagent is a frequently encountered problem. The DNPH (8.1) shall
be purified by multiple recrystallizations in UV grade acetonitrile (8.2). Recrystallization is accomplished,
at 40 °C to 60 °C, by slow evaporation of the solvent to maximize crystal size. Impurity levels of carbonyl
compounds in the DNPH are determined prior to use by HPLC and should be less than 0,15 µg per cartridge
and per individual compound.
Prepare a supersaturated solution of DNPH by boiling excess DNPH in 200 ml of acetonitrile for approximately
1 h. After 1 h, remove and transfer the supernatant to a covered beaker on a hot plate and allow gradual

oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
cooling to 40 °C to 60 °C. Maintain the solution at this temperature (40 °C) until a solvent with a volume
fraction of 95 % has evaporated. Decant the solution to waste and rinse the remaining crystals twice with
three times their apparent volume of acetonitrile. Transfer the crystals to another clean beaker, add 200 ml
of acetonitrile, heat to boiling, and again let crystals grow slowly at 40 °C to 60 °C until a solvent with a
volume fraction of 95 % has evaporated. Repeat this rinsing process.
Take an aliquot of the second rinse, dilute 10 times with acetonitrile, acidify with 1 ml of 3,8 mol/l perchloric
acid (8.3) per 100 ml of DNPH solution and analyse by HPLC, in accordance with 10.3.4.
Warning — Carry out this procedure under a properly ventilated hood and behind an explosion
shield.
NOTE An acid is necessary to catalyse the reaction of carbonyl compounds with DNPH. Most strong inorganic acids
such as hydrochloric, sulfuric, phosphoric or perchloric acids can be used satisfactorily. In rare cases, hydrochloric
and sulfuric acids cause problems.
An acceptable impurity level is less than 0,025 µg/ml of formaldehyde hydrazine in recrystallized DNPH
reagent or DNPH with a mass fraction of 0,02 %.
If the impurity level is not acceptable for the intended sampling application, repeat recrystallization.
Transfer the purified crystals to an all-glass reagent bottle, add 200 ml of acetonitrile, stopper, shake gently
and allow to stand overnight. Analyse the supernatant by HPLC in accordance with 10.3.4. If the impurity
level surpasses the acceptable limit, pipette off the solution to waste, then add 25 ml of acetonitrile to the
purified crystals. Repeat rinsing with 20 ml portions of acetonitrile until an acceptable low impurity level in
the supernatant is confirmed by HPLC analysis.
If the impurity level is acceptable, add another 25 ml of acetonitrile, stopper, shake the reagent bottle and
then set aside. The saturated solution above the purified crystals is the stock DNPH reagent. Maintain only a
minimum volume of saturated solution adequate for day-to-day operation. This minimizes waste of purified
reagent, should it be necessary to re-rinse the crystals to decrease the level of impurity for applications
requiring more stringent purity specifications. Use clean pipettes when removing saturated DNPH stock
solution for any analytical applications. Do not pour the stock solution from the reagent bottle.
9.2 Preparation of DNPH formaldehyde derivative
To a portion of the recrystallized DNPH (9.1), add a sufficient quantity of HCl of 2 mol/l (8.5) to obtain
an approximately saturated solution. Add formaldehyde (8.6) that is in molar excess of the DNPH to this
solution. Filter the DNPH-formaldehyde precipitate, wash it with HCl of 2 mol/l and water, and then allow it
to dry in air.
Check the purity of the DNPH-formaldehyde derivative by melting point determination (165 °C to 166 °C) or
HPLC analysis. If the impurity level is not acceptable, recrystallize the derivative in ethanol (8.8). Repeat the
purity check and recrystallize as necessary until an acceptable level of purity (e.g. mass fraction of 99 %) is
achieved.
The DNPH-formaldehyde derivative should be stored under refrigeration (4 °C) and protected from light. It
should be stable for at least six months. Storage under nitrogen (8.9) or argon further prolongs the lifetime
of the derivative.
Melting points of DNPH derivatives of several carbonyl compounds are given in Annex B.
DNPH derivatives of formaldehyde and other carbonyls (8.7) suitable for use as standards are commercially
available both in the form of pure crystals and as individual or mixed stock solutions in acetonitrile.
9.3 Preparation of DNPH formaldehyde standards
Prepare a standard stock solution of the DNPH-formaldehyde derivative by dissolving accurately weighed
amounts in acetonitrile (8.2). Prepare a working calibration standard mix from the standard stock solution.
The concentration of the DNPH-formaldehyde derivative in the standard mix solutions should be adjusted to
reflect the range of concentrations expected in real samples.

oSIST ISO/FDIS 16000-3:2026
ISO/FDIS 16000-3:2026(en)
Individual stock solutions of approximately 100 mg/l can be prepared by dissolving 10 mg of the solid
derivative in 100 ml of acetonitrile. The individual solution is used to prepare calibration standards
containing the derivative of interest at concentrations of 0,5 µg/ml to 20 µg/ml, that spans the concentration
of interest.
Store all standard solutions in tightly capped containers in a refrigerator and protected from light. Allow
them to equilibrate to room temperature before use. They should be replaced after four weeks.
9.4 Preparation of DNPH coated silica gel cartridges
9.4.1 General
This procedure shall be performed in an atmosphere with a very low aldehyde background concentration.
All glassware and plasticware shall be thoroughly cleaned and rinsed with deionized water and aldehyde-
free acetonitrile (8.2). Contact of reagents with laboratory air shall be minimized. Gloves shall be worn when
handling the cartridges.
9.4.2 DNPH coating solution
Pipette 30 ml of saturated DNPH stock solution into a 1 000 ml volumetric flask, then add 500 ml
acetonitrile (8.2). Acidify with 1,0 ml of concentrated HCl (8.5).
The atmosphere above the acidified solution should preferably be filtered through a DNPH-coated silica
gel cartridge, to minimize contamination from laboratory air. Shake solution, then make up to volume with
acetonitrile. Stopper the flask, invert and shake several times until the solution is homogeneous. Transfer
the acidified solution to a reagent bottle equipped with a positive-displacement dispenser of capacity in the
0 ml to 10 ml range.
Prime the dispenser and slowly dispense 10 ml to 20 ml to waste. Dispense an aliquot solution to a sample
vial and check the impurity level of the acidified solution by HPLC in accordance with 10.3.4. The impurity
level of formaldehyde should be <0,025 µg/ml.
9.4.3 Coating of silica gel cartridges
Open the cartridge package, connect the short end of the silica gel cartridge (7.1.1) to a 10 ml syringe,
and place it in the syringe rack (7.2.4) as illustrated in Figure 3. Using a positive-displacement repetitive
pipette (7.3.2.4), add 10 ml of acetonitrile (8.2) to each of the syringes. Let liquid drain to waste by gravity.
Remove any air bubbles that are trapped between the syringe and the silica cartridge by displacing them
with the acetonitrile in the syringe.
Set the repetitive dispenser, containing the acidified DNPH coating solution, to dispense 7 ml into the
cartridges. Once the effluent flow at the outlet of the cartridge has stopped, dispense 7 ml of the coating
reagent into each of the syringes. Let the coating reagent drain by gravity through the cartridge until flow at
the other end of the cartridge stops. Wipe away the excess liquid at the outlet of each of the cartridges with
clean tissue paper.
Assemble a drying manifold as shown in Figure 3 b). This contains a previously prepared DNPH-coated
cartridge at each of the exit ports (e.g. scrubber or “guard cartridges”). These “guard cartridges” serve to
remove traces of formaldehyde that can be present in the nitrogen (8.9) gas supply. They can be prepared
by drying a few of the newly coated cartridges according to the following instructions and testing these to
ensure the purity of the rest.
— Insert cartridge connectors [flared at both ends, 0,64 cm × 2,5 cm outside diameter polytetrafluoroethylene
(PTFE) tubing with the inside diameter slightly smaller than the outside diameter of the cartridge port]
on to the long end of the scrubber cartridges.
— Remove the cartridges from the syringes and connect the short ends of the cartridges to the open end of
the cartridge connectors already attached to the scrubber cartridges.

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ISO/FDIS 16000-3:2026(en)
— Pass nitrogen (8.9) through each of the cartridges at about 300 ml/min to 400 ml/min. Rinse the exterior
surfaces and outlet end of the cartridges with acetonitrile using a Pasteur pipette. After 15 min, stop the
flow of nitrogen, wipe the cartridge exterior free of acetonitrile and remove the dried cartridges. Plug
both ends of the coated cartridge with standard polypropylene male syringe plugs and place the plugged
cartridge in a borosilicate glass culture tube with polypropylene screw caps (7.2.1).
— Put a serial number and a lot number label on each of the individual cartridge glass storage containers
and refrigerate the prepared lot until use.
Sampling cartridges have been found to be stable for at least six months when stored at 4 °C in the absence
of light.
10 Procedure
10.1 Sample collection
Assemble the sampling system and ensure that the pump (7.1.2) is capable of constant flow rate throughout
the sampling period. The sampling cartridges (7.1.1) can be safely used for sampling air when the
temperature is above 10 °C. If required, add an ozone denuder or scrubber (see 5.2).
Before sample collection, check the system for leaks. Plug the inlet of the cartridge so no flow is indicated at
the outlet end of the pump. The flow meter should not indicate any air flow through the sampling apparatus.
For unattended or extended sampling periods, a mass flow controller (7.1.3) or, as appropriate, a compensated
personal sampling pump should be used to maintain constant flow. The flow controller should be set at least
20 % below the fixed maximum air flow rate through the cartridge.
NOTE 1 The silica gel is held in the cartridge between two fine-porosity filter frits. Air flow during sampling can
change as airborne particulates deposit on the front frit. The flow change can be significant when sampling particulate-
laden atmospheres.
Install the entire assembly (including a “dummy” sampling cartridge) and check the flow rate at a value
near the desired rate. Flow rates of 0,5 l/min to 1,2 l/min shall be employed. The total number of moles of
carbonyl in the volume of air sampled shall not exceed that of the DNPH (2 mg or 0,01 mol/cartridge; 1 mg to
2 mg/cartridge for commercially available pre-coated cartridges). In general, a safe estimate of the sample
size should be lower than 75 % of the DNPH mass loading of the cartridge [100 µg to 200 µg as HCHO, with
respect to interferences to be taken into account (see Clause 5)]. Generally, calibration can be accomplished
using a soap-bubble flow meter or calibrated wet test meter (7.1.4) connected to the flow exit, assuming the
system is le
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