ASTM D1840-22

Standard Test Method for Naphthalene Hydrocarbons in Aviation Turbine Fuels by Ultraviolet Spectrophotometry

SIGNIFICANCE AND USE
5.1 This test method for naphthalene hydrocarbons is one of a group of tests used to assess the combustion characteristics of aviation turbine fuels of the kerosene boiling range. The naphthalene hydrocarbon content is determined because naphthalenes, when burned, tend to have a relatively larger contribution to a sooty flame, smoke, and thermal radiation than single ring aromatics.
SCOPE
1.1 This test method covers the determination, by ultraviolet spectrophotometry, of the total concentration of naphthalene, acenaphthene, and alkylated derivatives of these hydrocarbons in jet fuels. This test method is designed to analyze fuels containing not more than 5 % of such components and having end points below 315 °C (600 °F). The range of concentrations used in the interlaboratory test programs which established the precision statements for this test method was 0.08 % to 5.6 % by volume. This test method determines the maximum amount of naphthalenes that could be present.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see 8.1 and 8.2.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Dec-2022
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.04.0F - Absorption Spectroscopic Methods

Relations

• Refers: ASTM E169-04(2014) - Standard Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
• Effective Date: 01-Aug-2014
• Refers: ASTM E131-10 - Standard Terminology Relating to Molecular Spectroscopy
• Effective Date: 01-Mar-2010
• Refers: ASTM E169-04(2009) - Standard Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
• Effective Date: 01-Oct-2009
• Refers: ASTM E275-08 - Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
• Effective Date: 15-Oct-2008
• Refers: ASTM E131-05 - Standard Terminology Relating to Molecular Spectroscopy
• Effective Date: 01-Sep-2005
• Refers: ASTM E169-04 - Standard Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
• Effective Date: 01-Nov-2004
• Refers: ASTM E131-02 - Standard Terminology Relating to Molecular Spectroscopy
• Effective Date: 10-Sep-2002
• Refers: ASTM E275-01 - Standard Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers
• Effective Date: 10-Feb-2001
• Refers: ASTM E275-93 - Standard Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near-Infrared Spectrophotometers
• Effective Date: 10-Feb-2001
• Refers: ASTM E131-00a - Standard Terminology Relating to Molecular Spectroscopy
• Effective Date: 10-Sep-2000
• Refers: ASTM E169-99 - Standard Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
• Effective Date: 10-Feb-1999

Overview

ASTM D1840-22 specifies the standard test method for determining the concentration of naphthalene hydrocarbons in aviation turbine (jet) fuels using ultraviolet (UV) spectrophotometry. This standard, developed by ASTM International, is integral for assessing the combustion characteristics of kerosene-range aviation fuels, focusing particularly on identifying naphthalene, acenaphthene, and their alkylated derivatives. Excessive levels of these hydrocarbons are significant because, when combusted, naphthalenes are more prone to producing sooty flames, smoke, and increased thermal radiation compared to single ring aromatics.

This method is suitable for jet fuels containing up to 5% of these components by volume, and is designed for products with a boiling endpoint below 315°C (600°F). The range of tested concentrations in the original method validation was between 0.08% and 5.6% by volume.

Key Topics

• Test Principle: The method utilizes ultraviolet spectrophotometry to measure the absorbance of a jet fuel sample solution at 285 nm. The absorbance correlates with the total naphthalene hydrocarbon concentration.
• Sample Limits: Designed for fuels with no more than 5% naphthalene, acenaphthene, and their alkyl derivatives.
• Spectrophotometer Specifications: Uses precise wavelength and absorbance calibration with a repeatability standard of ±0.5%, ensuring reliable quantification.
• Interferences: Certain aromatic compounds (e.g., phenanthrenes, dibenzothiophenes) can contribute to apparent naphthalene content, but the boiling endpoint restriction minimizes most interference.
• Dilution and Calibration Procedures: The standard provides detailed instructions for dilution and calibration to keep absorbance readings within an optimal range, enhancing reproducibility.
• Reporting: Results are reported to the nearest 0.01% by volume.
• Precision and Bias: Repeatability and reproducibility are defined based on interlaboratory studies, ensuring industry-accepted levels of reliability.

Applications

• Aviation Fuel Quality Control: Ensuring that jet fuels conform to industry safety and performance requirements by monitoring aromatic content, especially naphthalenes, which affect combustion by increasing soot and smoke.
• Regulatory Compliance: Used by fuel manufacturers, suppliers, and laboratories to meet domestic and international aviation fuel standards.
• Research and Development: Supports the formulation of cleaner and more efficient aviation turbine fuels by providing accurate measurement of potentially problematic aromatic hydrocarbons.
• Military and Civil Aviation: Referenced by agencies such as the U.S. Department of Defense for jet fuel procurement and quality assurance.

Related Standards

• ASTM E131: Terminology Relating to Molecular Spectroscopy - provides definitions for spectroscopy-related terms utilized in this test method.
• ASTM E169: Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis - offers foundational practices for UV-Vis analysis.
• ASTM E275: Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers - addresses instrument calibration and performance checks relevant to ASTM D1840-22.

Practical Value

Adhering to ASTM D1840-22 enables aviation fuel stakeholders to objectively measure and control naphthalene hydrocarbon content, contributing to improved engine performance, reduced emissions, and increased regulatory compliance. This standard is a cornerstone in the aviation industry’s efforts to produce and maintain safe, efficient, and environmentally responsible jet fuels through proven ultraviolet spectrophotometric techniques.

For further technical details, users should consult the official ASTM D1840-22 publication and ensure compliance with health, safety, and environmental guidelines as stated by ASTM International.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D1840 − 22
Standard Test Method for
Naphthalene Hydrocarbons in Aviation Turbine Fuels by
Ultraviolet Spectrophotometry
This standard is issued under the fixed designation D1840; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* E169 PracticesforGeneralTechniquesofUltraviolet-Visible
Quantitative Analysis
1.1 Thistestmethodcoversthedetermination,byultraviolet
E275 Practice for Describing and Measuring Performance of
spectrophotometry, of the total concentration of naphthalene,
Ultraviolet and Visible Spectrophotometers
acenaphthene, and alkylated derivatives of these hydrocarbons
in jet fuels. This test method is designed to analyze fuels
3. Terminology
containing not more than 5 % of such components and having
end points below 315 °C (600 °F).The range of concentrations 3.1 Definitions:
used in the interlaboratory test programs which established the
3.1.1 Definitions of terms and symbols relating to absorp-
precision statements for this test method was 0.08 % to 5.6 %
tion spectroscopy in this test method shall conform to Termi-
by volume. This test method determines the maximum amount
nology E131. Terms of particular significance are the follow-
of naphthalenes that could be present.
ing:
3.1.2 radiant energy, n—energy transmitted as electromag-
1.2 The values stated in SI units are to be regarded as
netic waves.
standard. No other units of measurement are included in this
standard.
3.1.3 radiant power, P, n—rate at which energy is trans-
ported in a beam of radiant energy.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 absorbance, A, n—the molecular property of a sub-
priate safety, health, and environmental practices and deter-
stance that determines its ability to take up radiant power,
mine the applicability of regulatory limitations prior to use.
expressed by
For specific warning statements, see 8.1 and 8.2.
A 5 log 1/T 52log T (1)
~ !
10 10
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
where:
ization established in the Decision on Principles for the
T = transmittance as defined in 3.2.5.
Development of International Standards, Guides and Recom-
3.2.1.1 Discussion—It may be necessary to correct the
mendations issued by the World Trade Organization Technical
observed transmittance (indicated by the spectrophotometer)
Barriers to Trade (TBT) Committee.
by compensating for reflectance losses, solvent absorption
losses, or refraction effects.
2. Referenced Documents
3.2.2 absorptivity, a, n—the specific property of a substance
2.1 ASTM Standards:
to absorb radiant power per unit sample concentration and path
E131 Terminology Relating to Molecular Spectroscopy
length, expressed by
a 5 A/bc (2)
This test method is under the jurisdiction of ASTM Committee D02 on
where:
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.04.0F on Absorption Spectroscopic Methods. A = absorbance defined in 3.2.1,
Current edition approved Dec. 15, 2022. Published January 2023. Originally
b = sample cell path length, and
approved in 1961. Last previous edition approved in 2017 as D1840 – 07 (2017).
c = quantity of absorbing substance contained in a unit
DOI: 10.1520/D1840-22.
volume of solvent.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.2.2.1 Discussion—Quantitative ultraviolet analyses are
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. based upon the absorption law, known as Beer’s law. The law
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1840 − 22
TABLE 1 Interfering Compounds
statesthattheabsorbanceofahomogeneoussamplecontaining
an absorbing substance is directly proportional to the concen- Error in Percentage of
Type of Interfering Compound Naphthalenes Caused by 1 %
tration of the absorbing substance at a single wavelength,
Interfering Compound
expressed by
Phenanthrenes 2
Dibenzothiophenes 2
A 5 abc (3)
Biphenyls 1
Benzothiophenes 0.6
where:
Anthracenes 0.1
A = absorbance as defined in 3.2.1,
a = absorptivity as defined in 3.2.2,
b = sample cell path length, and
c = quantity of absorbing substance contained in a unit spectral slit width of 1 nm or less. Wavelength measurements
volume of solvent. shall be repeatable and known to be accurate within 0.1 nm or
less as measured by mercury emission line at 253.65 nm or the
3.2.3 concentration, c, n—the quantity of naphthalene hy-
absorptionspectrumofeitherholmiumoxideglassat287.5 nm
drocarbons in grams per litre of isooctane.
or holmium oxide solution at 287.1 nm. At the 0.4 absorbance
3.2.4 sample cell path length, b, n—the distance, in
level in the spectral region between 240 nm and 300 nm, ab-
centimetres, measured in the direction of propagation of the
sorbance measurements shall be repeatable within 60.5 % or
beam of radiant energy, between the surfaces of the specimen
better. In the absorbance range encompassing 0.2 to 0.8, the
on which the radiant energy is incident and the surface of the
photometric accuracy shall not differ by more than 60.5 % of
specimen from which it is emergent.
samples whose absorbance has been established by a standard-
3.2.4.1 Discussion—This distance does not include the
izing laboratory.
thickness of the cell in which the specimen is contained.
7.1.1 Discussion—Many manufacturers provide secondary
3.2.5 transmittance, T, n—the molecular property of a sub-
standards, traceable to NIST primary standards, for checking
stance that determines its transportability of radiant power
the wavelength accuracy and photometric accuracy of spectro-
expressed by
photometers. These materials may be used to verify spectro-
photometer performance provided that they have been recali-
T 5 P/P (4)
o
brated periodically as recommended by the manufacturer.
where:
7.2 It shall be initially and thereafter periodically demon-
P = radiant power passing through the sample, and
strated that an instrument can be operated in a manner to give
P = radiant power incident upon the sample.
o
test results equivalent to those described in 7.1.
4. Summary of Test Method
NOTE 1—For recommended methods of testing spectrophotometers to
be used in this test method, refer to Practice E275. Other preferred
4.1 The total concentration of naphthalenes in jet fuels is
alternatives to those in 7.1 are potassium dichromate in perchloric acid
determined by measurement of the absorbance at 285 nm of a
(NIST SRM 935 series as described in Practice E275) for photometric
solution of the fuel at known concentration.
accuracy and a 20 mg⁄Lhigh (>99 %) purity naphthalene in spectroscopic
grade isooctaneforwavelengthaccuracy.Thelatterhasaminormaximum
5. Significance and Use
at 285.7 nm. The naphthalene solution shall not be used for photometric
accuracy.
5.1 This test method for naphthalene hydrocarbons is one of
agroupoftestsusedtoassessthecombustioncharacteristicsof
7.3 Vitreous Silica Cells, two, having path lengths of
aviation turbine fuels of the kerosene boiling range. The
1.00 cm 6 0.005 cm.
naphthalene hydrocarbon content is determined because
7.4 Pipets, Class A.
naphthalenes, when burned, tend to have a relatively larger
7.5 Lens Paper.
contribution to a sooty flame, smoke, and thermal radiation
than single ring aromatics.
7.6 Balance, capable of taring or weighing 100 g to the
nearest0.0001 g.Thebalanceshallbeaccurateto 60.0002 gat
6. Interferences
a 100 g load.
6.1 Interferences add to the apparent naphthalene content.
8. Solvents
Phenanthrenes, dibenzothiophenes, biphenyls,
benzothiophenes, and anthracenes interfere if present. The end
8.1 Spectroscopic 2,2,4 Trimethylpentane (Isooctane).
point limitation of 315 °C will minimize this interference
(Warning—Isooctane is extremely flammable, harmful if in-
except for benzothiophenes and biphenyls. The contribution to
haled.)
measured naphthalene content by the presence of 1 % of such
NOTE 2—Spectroscopic-grade isooctane is available commercially.
interfering compounds can be estimated from Table 1.
Technical-grade isooctane is a satisfactory base stock for the preparation
6.2 Saturated hydrocarbons, olefins, thiophenes, and alkyl of spectroscopic solvent. Allow about 4 L or 5 L of this material to
percolate through a column of activated silica gel (74 µm) 50.8 mm to
or cycloalkyl derivatives of benzene will not interfere.
76.2 mm in diameter and 0.6 m to 0.9 m in depth. Collect only the portion
of the solvent that h
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D1840 − 07 (Reapproved 2017) D1840 − 22
Standard Test Method for
Naphthalene Hydrocarbons in Aviation Turbine Fuels by
Ultraviolet Spectrophotometry
This standard is issued under the fixed designation D1840; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope Scope*
1.1 This test method covers the determination, by ultraviolet spectrophotometry, of the total concentration of naphthalene,
acenaphthene, and alkylated derivatives of these hydrocarbons in jet fuels. This test method is designed to analyze fuels containing
not more than 5 % of such components and having end points below 315 °C (600 °F); however, the (600 °F). The range of
concentrations used in the interlaboratory test programs which established the precision statements for this test method were
0.03 % to 4.25 % by volume for Procedure A, and was 0.08 % to 5.6 % by volume for Procedure B. volume. This test method
determines the maximum amount of naphthalenes that could be present.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. For specific warning statements, see 8.1 and 8.2.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E131 Terminology Relating to Molecular Spectroscopy
E169 Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
3. Terminology
3.1 Definitions:
3.1.1 Definitions of terms and symbols relating to absorption spectroscopy in this test method shall conform to Terminology E131.
Terms of particular significance are the following:
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.04.0F on Absorption Spectroscopic Methods.
Current edition approved Oct. 1, 2017Dec. 15, 2022. Published November 2017January 2023. Originally approved in 1961. Last previous edition approved in 20132017
as D1840 – 07 (2013).(2017). DOI: 10.1520/D1840-07R17.10.1520/D1840-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1840 − 22
3.1.2 radiant energy, n—energy transmitted as electromagnetic waves.
3.1.3 radiant power, P, n—rate at which energy is transported in a beam of radiant energy.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorbance, A, n—the molecular property of a substance that determines its ability to take up radiant power, expressed by
A 5 log ~1/T! 52log T (1)
10 10
where:
T = transmittance as defined in 3.2.5.
3.2.1.1 Discussion—
It may be necessary to correct the observed transmittance (indicated by the spectrophotometer) by compensating for reflectance
losses, solvent absorption losses, or refraction effects.
3.2.2 absorptivity, a, n—the specific property of a substance to absorb radiant power per unit sample concentration and path length,
expressed by
a 5 A/bc (2)
where:
A = absorbance defined in 3.2.1,
b = sample cell path length, and
c = quantity of absorbing substance contained in a unit volume of solvent.
3.2.2.1 Discussion—
Quantitative ultraviolet analyses are based upon the absorption law, known as Beer’s law. The law states that the absorbance of
a homogeneous sample containing an absorbing substance is directly proportional to the concentration of the absorbing substance
at a single wavelength, expressed by
A 5 abc (3)
where:
A = absorbance as defined in 3.2.1,
a = absorptivity as defined in 3.2.2,
b = sample cell path length, and
c = quantity of absorbing substance contained in a unit volume of solvent.
3.2.3 concentration, c, n—the quantity of naphthalene hydrocarbons in grams per litre of isooctane.
3.2.4 sample cell path length, b, n—the distance, in centimetres, measured in the direction of propagation of the beam of radiant
energy, between the surfaces of the specimen on which the radiant energy is incident and the surface of the specimen from which
it is emergent.
3.2.4.1 Discussion—
This distance does not include the thickness of the cell in which the specimen is contained.
3.2.5 transmittance, T, n—the molecular property of a substance that determines its transportability of radiant power expressed by
T 5 P/P (4)
o
where:
P = radiant power passing through the sample, and
P = radiant power incident upon the sample.
o
D1840 − 22
4. Summary of Test Method
4.1 The total concentration of naphthalenes in jet fuels is determined by measurement of the absorbance at 285 nm of a solution
of the fuel at known concentration.
5. Significance and Use
5.1 This test method for naphthalene hydrocarbons is one of a group of tests used to assess the combustion characteristics of
aviation turbine fuels of the kerosene boiling range. The naphthalene hydrocarbon content is determined because naphthalenes,
when burned, tend to have a relatively larger contribution to a sooty flame, smoke, and thermal radiation than single ring aromatics.
6. Interferences
6.1 Interferences add to the apparent naphthalene content. Phenanthrenes, dibenzothiophenes, biphenyls, benzothiophenes, and
anthracenes interfere if present. The end point limitation of 315 °C will minimize this interference except for benzothiophenes and
biphenyls. The contribution to measured naphthalene content by the presence of 1 % of such interfering compounds can be
estimated from Table 1.
6.2 Saturated hydrocarbons, olefins, thiophenes, and alkyl or cycloalkyl derivatives of benzene will not interfere.
7. Apparatus
7.1 Spectrophotometer, equipped to measure the absorbance of solutions in the spectral region 240 nm to 300 nm with a spectral
slit width of 1 nm or less. Wavelength measurements shall be repeatable and known to be accurate within 0.1 nm or less as
measured by mercury emission line at 253.65 nm or the absorption spectrum of either holmium oxide glass at 287.5 nm or
holmium oxide solution at 287.1 nm. At the 0.4 absorbance level in the spectral region between 240 nm and 300 nm, absorbance
measurements shall be repeatable within 60.5 % or better. In the absorbance range encompassing 0.2 to 0.8, the photometric
accuracy shall not differ by more than 60.5 % of samples whose absorbance has been established by a standardizing laboratory.
7.1.1 Discussion—Many manufacturers provide secondary standards, traceable to NIST primary standards, for checking the
wavelength accuracy and photometric accuracy of spectrophotometers. These materials may be used to verify spectrophotometer
performance provided that they have been recalibrated periodically as recommended by the manufacturer.
7.2 It shall be initially and thereafter periodically demonstrated that an instrument can be operated in a manner to give test results
equivalent to those described in 7.1.
NOTE 1—For recommended methods of testing spectrophotometers to be used in this test method, refer to Practice E275. Other preferred alternatives to
those in 7.1 are potassium dichromate in perchloric acid (NIST SRM 935 series as described in Practice E275) for photometric accuracy and a 20 mg ⁄L
high (>99 %) purity naphthalene in spectroscopic grade isooctane for wavelength accuracy. The latter has a minor maximum at 285.7 nm. The naphthalene
solution shall not be used for photometric accuracy.
7.3 Vitreous Silica Cells, two, having path lengths of 1.00 cm 6 0.005 cm.
7.4 Pipets, Class A.
7.5 Lens Paper.
TABLE 1 Interfering Compounds
Error in Percentage of
Type of Interfering Compound Naphthalenes Caused by 1 %
Interfering Compound
Phenanthrenes 2
Dibenzothiophenes 2
Biphenyls 1
Benzothiophenes 0.6
Anthracenes 0.1
D1840 − 22
7.6 Balance, capable of taring or weighing 100 g to the nearest 0.0001 g. The balance shall be accurate to 60.0002 g at a 100 g
load.
8. Solvents
8.1 Spectroscopic 2,2,4 Trimethylpentane (Isooctane). (Warning—Isooctane is extremely flammable, harmful if inhaled.)
NOTE 2—Spectroscopic-grade isooctane is available commercially. Technical-grade isooctane is a satisfactory base stock for the preparation of
spectroscopic solvent. Allow about 4 L or 5 L of this material to percolate through a column of activated silica gel (74 μm) 50.8 mm to 76.2 mm in
diameter and 0.6 m to 0.9 m in depth. Collect only the portion of the solvent that has a transmission compared to distilled water greater than 90 % over
the entire spectral range from 240 nm to 300 nm. Store in scrupulously clean glass-stoppered bottles and always keep covered. In general it will be best
to use a fresh portion of silica gel in preparing a new batch of solvent. However the gel can be reactivated by pouring 500 mL of acetone through the
column, draining, drying by suction, and heating the gel in thin layers in an oven at 400 °C until white color is restored. Activated silica gel is stored
in closed containers.
8.2 Solvents for Cleaning Cells—Acetone or ethyl alcohol (Warning—Acetone and ethyl alcohol are extremely flammable and
can be harmful if inhaled), with residue after evaporation no greater than 10 mg ⁄kg.
NOTE 3—The 10 mg ⁄kg is the American Chemical Society (ACS) reagent grade maximum specification. An ACS reagent grade solvent may be used
without further testing.
9. Calibration and Standardization
9.1 Instead of direct calibration of the spectrophotometer with known naphthalenes, the average absorptivity of the C to C
10 13
naphthalenes at 285 nm can be taken at 33.7 L ⁄g·cm. The data used to calculate this average are given in Table 2.
10. Procedure A—Serial Dilution
NOTE 4—The user may use alternative Procedure B if preferred.
10.1 For recommended techniques, refer to Practices E169. Check carefully sections on handling and cleaning of cells and
glassware, instrument adjustments, and method of absorbance measurement.
10.2 Sample Preparation—Prepare three dilutions of the sample as follows:Add an appropriate mass of sample to a clean, dry,
tared 100 mL volumetric flas
...