ASTM D8478-23

Standard Test Method for N-Hexane Recoverable Total Oil and Grease and Total Petroleum Hydrocarbons in Water by ATR-Infrared Determination

SIGNIFICANCE AND USE
5.1 The presence and concentration of oil and grease in domestic and industrial wastewater is of concern to the public because of its deleterious aesthetic effect and its impact on aquatic life.  
5.2 Regulations and standards have been established that require monitoring of TOG and TPH in produced water and wastewater.
SCOPE
1.1 This test method covers the determination of total oil and grease, and total petroleum hydrocarbons in produced water and wastewater by an infrared (IR) determination of n-hexane extractable substances from the sample. Included in this estimation of total oil and grease are any other compounds soluble in the n-hexane.  
1.2 This test method defines total oil and grease in produced water and wastewater as that which is extractable in the test method and measured by IR absorption from 3.34 µm to 3.54 µm (2825 cm-1 to 2994 cm-1). Similarly, this test method defines total petroleum hydrocarbons in produced water and wastewater as that oil and grease which is not adsorbed by silica gel in the test method, and is measured by IR absorption from 3.34 µm to 3.54 µm (2825 cm-1 to 2994 cm-1). Alternative methods for total oil and grease or total petroleum hydrocarbons, or both, can produce differing results.  
1.3 This method covers the range of 5 mg/L to 175 mg/L for total oil and grease and the range of 5 mg/L to 50 mg/L for total petroleum hydrocarbons. The range may be extended to a lower or higher level by extraction of a larger or smaller sample volume collected separately.  
1.4 This test method uses horizontal attenuated total reflectance (HATR) with a cubic zirconia crystal.  
1.5 This test method is intended as a field test only and should be treated as such. This method is not intended to replace laboratory-based regulatory methods currently in use.  
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.7 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. See Guide D3856 for more information.  
1.8 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-Apr-2023
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.06 - Methods for Analysis for Organic Substances in Water

Relations

• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D3856-11 - Standard Guide for Management Systems in Laboratories Engaged in Analysis of Water
• Effective Date: 15-Nov-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D3370-07 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2007
• Refers: ASTM D1129-06ae1 - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006
• Refers: ASTM D1129-06a - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006
• Refers: ASTM D2777-06 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Aug-2006
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM E168-06 - Standard Practices for General Techniques of Infrared Quantitative Analysis (Withdrawn 2015)
• Effective Date: 01-Mar-2006
• Refers: ASTM D1129-06 - Standard Terminology Relating to Water
• Effective Date: 15-Feb-2006
• Refers: ASTM D3856-95(2006) - Standard Guide for Good Laboratory Practices in Laboratories Engaged in Sampling and Analysis of Water
• Effective Date: 15-Feb-2006

Overview

ASTM D8478-23 is a standard test method developed by ASTM International for the reliable determination of N-hexane recoverable total oil and grease (TOG) as well as total petroleum hydrocarbons (TPH) in produced water and wastewater. Using Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy, the standard enables rapid field-based quantification of extractable organic material, supporting environmental monitoring and regulatory compliance for domestic, industrial, and oil production wastewater streams.

This test method is especially valuable for its ability to provide field-based analysis, guiding timely decisions regarding wastewater treatment and discharge-but it does not replace comprehensive laboratory-based regulatory testing.

Key Topics

• Test Scope: Covers the analysis of total oil and grease, and total petroleum hydrocarbons in water samples via IR measurement of n-hexane extractables.
• Measurement Range: Applicable for TOG from 5 mg/L to 175 mg/L, and TPH from 5 mg/L to 50 mg/L, with flexibility for lower or higher concentrations through sample volume adjustments.
• ATR-IR Technology: Utilizes horizontal attenuated total reflectance (HATR) with a cubic zirconia crystal to measure extract absorption in the IR range 3.34 μm to 3.54 μm (2825 cm⁻¹ to 2994 cm⁻¹).
• Sample Types: Suitable for both produced water (from oil and gas operations) and general domestic or industrial wastewater.
• Extraction Specificity: Not only targets oil and grease but also any n-hexane soluble compounds; employs silica gel treatment to distinguish non-polar TPH fractions.
• Field Use: Designed for field analysis with clear guidelines on calibration, quality control, and matrix interferences.
• Regulatory Context: Supports monitoring to comply with environmental regulations requiring the measurement of oil, grease, and petroleum hydrocarbons in water.

Applications

Implementing ASTM D8478-23 provides several practical benefits for industries and environmental authorities:

• Wastewater Monitoring: Enables on-site assessment of oil and grease contamination in effluent streams from industrial, municipal, and oil & gas operations.
• Environmental Compliance: Assists facilities in meeting established regulatory limits for TOG and TPH before environmental discharge, protecting aquatic life and public aesthetics.
• Process Control: Delivers immediate feedback for operators adjusting treatment processes or managing accidental hydrocarbon releases.
• Site Assessments and Spill Response: Facilitates initial screening in environmental impact evaluations, including oil spill or contamination events, where rapid results are critical.
• Cost Effectiveness: Reduces laboratory turnaround times and transport costs for preliminary screening, allowing for targeted laboratory confirmation when needed.
• Data Consistency: Adheres to a recognized international framework for data comparability and repeatability, essential for standardized reporting and audits.

Related Standards

ASTM D8478-23 aligns with and complements a range of international and national standards for water analysis and environmental protection, including:

• ASTM D3856 - Guide for Management Systems in Laboratories Engaged in Analysis of Water
• ASTM D1129/D1193/D2777/D3370/D5847 - Terminology, water specifications, and practices for sampling and quality control in water analysis
• EPA Method 1664, Revision A - Standard for n-hexane extractable material (oil and grease) analysis by gravimetry
• 40 CFR Part 136 - US EPA guidelines for test procedures related to pollutant analysis in water
• 49 CFR Part 172 - US Department of Transportation standards related to hazardous material handling in sampling and analysis
• ASTM E168 - Practices for general techniques of infrared quantitative analysis

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Keywords: ASTM D8478-23, total oil and grease, TOG, total petroleum hydrocarbons, TPH, ATR-IR, infrared spectroscopy, n-hexane extraction, wastewater analysis, environmental compliance, field test, oil in water, industrial water quality, water monitoring, standard test method, petroleum hydrocarbons, produced water, silica gel, cubic zirconia crystal.

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: D8478 − 23
Standard Test Method for
N-Hexane Recoverable Total Oil and Grease and Total
Petroleum Hydrocarbons in Water by ATR-Infrared
Determination
This standard is issued under the fixed designation D8478; 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.
1. Scope 1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method covers the determination of total oil
responsibility of the user of this standard to establish appro-
and grease, and total petroleum hydrocarbons in produced
priate safety, health, and environmental practices and deter-
water and wastewater by an infrared (IR) determination of
mine the applicability of regulatory limitations prior to use.
n-hexane extractable substances from the sample. Included in
See Guide D3856 for more information.
this estimation of total oil and grease are any other compounds
1.8 This international standard was developed in accor-
soluble in the n-hexane.
dance with internationally recognized principles on standard-
1.2 This test method defines total oil and grease in produced
ization established in the Decision on Principles for the
water and wastewater as that which is extractable in the test
Development of International Standards, Guides and Recom-
method and measured by IR absorption from 3.34 μm to
mendations issued by the World Trade Organization Technical
-1 -1
3.54 μm (2825 cm to 2994 cm ). Similarly, this test method
Barriers to Trade (TBT) Committee.
defines total petroleum hydrocarbons in produced water and
wastewater as that oil and grease which is not adsorbed by
2. Referenced Documents
silica gel in the test method, and is measured by IR absorption
-1 -1
2.1 ASTM Standards:
from 3.34 μm to 3.54 μm (2825 cm to 2994 cm ). Alternative
D1129 Terminology Relating to Water
methods for total oil and grease or total petroleum
D1193 Specification for Reagent Water
hydrocarbons, or both, can produce differing results.
D2777 Practice for Determination of Precision and Bias of
1.3 This method covers the range of 5 mg/L to 175 mg/L for
Applicable Test Methods of Committee D19 on Water
total oil and grease and the range of 5 mg/L to 50 mg/L for total
D3370 Practices for Sampling Water from Flowing Process
petroleum hydrocarbons. The range may be extended to a
Streams
lower or higher level by extraction of a larger or smaller
D3856 Guide for Management Systems in Laboratories
sample volume collected separately.
Engaged in Analysis of Water
D5847 Practice for Writing Quality Control Specifications
1.4 This test method uses horizontal attenuated total reflec-
for Standard Test Methods for Water Analysis
tance (HATR) with a cubic zirconia crystal.
E168 Practices for General Techniques of Infrared Quanti-
1.5 This test method is intended as a field test only and
tative Analysis
should be treated as such. This method is not intended to
2.2 CFR Publications:
replace laboratory-based regulatory methods currently in use.
40 CFR Part 136 Guidelines Establishing Test Procedures
1.6 The values stated in SI units are to be regarded as
for the Analysis of Pollutants
standard. No other units of measurement are included in this
49 CFR Part 172 Hazardous Materials Table, Special
standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee D19 on Water contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
and is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for Standards volume information, refer to the standard’s Document Summary page on
Organic Substances in Water. the ASTM website.
Current edition approved April 15, 2023. Published May 2023. DOI: 10.1520/ Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St.,
D8478-23. NW, Washington, DC 20401, http://www.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8478 − 23
Provisions, Hazardous Materials Communications, Emer- 6. Interferences
gency Response Information, Training Requirements, and
6.1 Soaps, detergents, surfactants, and other materials can
Security Plans
form emulsions that can reduce the amount of oil and grease
2.3 EPA Standards:
extracted from a sample. This test method contains procedures
Method 1664, Revision A N-Hexane Extractable Material
that can assist the analyst in breaking such emulsions.
(HEM; Oil and Grease) and Silica Gel Treated N-Hexane
6.2 Organic compounds and other materials not considered
Extractable Material (SGTHEM; Non-polar Material) by
as oil and grease on the basis of chemical structure can be
Extraction and Gravimetry
extracted and measured as total oil and grease. Of those
measured, certain ones will be adsorbed by silica gel while
3. Terminology
others will not. Those not adsorbed are measured as total
3.1 Definitions:
petroleum hydrocarbons.
3.1.1 For definitions of terms used in this test method, refer
6.3 Sulfur present in the sample can extract into n-hexane
to Terminology D1129 and Practices E168.
and cause a positive bias in the results. See Annex A2 for
3.2 Definitions of Terms Specific to This Standard:
testing details.
3.2.1 horizontal attenuated total reflection (HATR) crystal,
n—horizontally oriented infrared transmitting crystal shaped so
7. Apparatus
that light will pass through the filter while reflecting off the top
7.1 Filter Paper, ashless, quantitative, general-purpose,
and bottom crystal face; as light strikes the top crystal the light
11 cm diameter, 8 μm pore size.
will be attenuated by any sample placed on the top crystal at
specific wavelengths corresponding to the molecular shape and
7.2 Glass Sample Bottle, minimum 125 mL, with screw cap
chemistry of the sample; this attenuation can be used to
having a fluoropolymer liner.
generate an infrared spectrum of the sample.
7.3 Glass Graduated Cylinder, 100 mL
3.2.2 total oil and grease (TOG), n—organic material that
7.4 Glass Funnel.
can be extracted from produced water or wastewater by this
test method and which can be measured by infrared absorption 7.5 Volumetric Flasks, glass, various.
in the region from 3.34 μm to 3.54 μm.
7.6 Polytetrafluoroethylene (PTFE) Spritz Bottle, one-piece
3.2.3 total petroleum hydrocarbon (TPH), n—non-polar or-
wash bottle for rinsing.
ganic material that can be extracted from produced water or
7.7 Syringes, 100 μL, 25 mL.
wastewater, and which can be measured by infrared absorption
7.8 Glass Separatory-Funnel, 500 mL, with fluoropolymer
in the region from 3.34 μm to 3.54 μm.
stopcock and stopper (optional).
4. Summary of Test Method
7.9 Volumetric Pipettes, glass, various (optional).
4.1 A sample of produced water or wastewater between
7.10 Analytical Balance (optional).
100 mL and 250 mL is extracted with a proportional amount of
7.11 Infrared Analyzer, scanning or non-scanning, capable
n-hexane at a ratio of 10:1 (sample to n-hexane). A portion of
-1
of measuring absorption from 3.34 μm to 3.54 μm (2825 cm
the extract is evaporated on the HATR crystal and examined by
-1
to 2994 cm ). In order for the analyzer to comply, the standard
infrared spectroscopy (IR) for a total oil and grease measure-
deviation of 10 measurements with no sample present shall not
ment. If a total petroleum hydrocarbons measurement is
exceed 0.1 mAU.
required, a portion of the extract is contacted with silica gel to
7.11.1 HATR Crystal. The apparatus shall use a cubic
remove polar substances, thereby producing a solution contain-
zirconia HATR crystal which contains a trough that prevents
ing non-polar material. The non-polar material is measured by
the n-hexane from spreading off the crystal.
infrared spectroscopy.
8. Reagents and Materials
5. Significance and Use
5.1 The presence and concentration of oil and grease in 8.1 Purity of Reagents—Spectroscopic grade (preferred) or
reagent grade chemicals shall be used in tests. Unless other-
domestic and industrial wastewater is of concern to the public
because of its deleterious aesthetic effect and its impact on wise indicated, it is intended that all reagents shall conform to
the specifications of the committee on analytical reagents of the
aquatic life.
American Chemical Society, where such specifications are
5.2 Regulations and standards have been established that
available. Other grades may be used, provided it is first
require monitoring of TOG and TPH in produced water and
wastewater.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Available from United States Environmental Protection Agency (EPA), William Standard-Grade Reference Materials, American Chemical Society, Washington,
Jefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460, DC. For suggestions on the testing of reagents not listed by the American Chemical
http://www.epa.gov. Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
Consult the manufacturer’s operation manual for the specific instructions U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
related to the infrared spectrometer or analyzer to be used. copeial Convention, Inc. (USPC), Rockville, MD.
D8478 − 23
ascertained that the reagent is of sufficiently high purity to are biased low precludes the collection of composite samples
permit its use without lessening the accuracy of the determi- for determination of TOG and TPH. Therefore, samples must
nation. be collected as grab samples. If a composite measurement is
required, individual grab samples collected at prescribed time
8.2 Purity of Water—Unless otherwise indicated, references
intervals may be analyzed separately and the concentrations
to laboratory or reagent water shall be understood to mean
averaged.
reagent water conforming to Specification D1193, Type II.
9.3 Preserve the sample with a sufficient quantity of either
8.3 Isopropyl Alcohol—95 % minimum purity.
sulfuric acid (see 8.10) or hydrochloric acid (see 8.11) to a pH
8.4 n-Hexane—95 % minimum purity, evaporation residue
of 2 or lower and refrigerate at 2 °C to 6 °C from the time of
less than 5 mg/L. Used for extraction.
collection until extraction. The amount of acid required will be
dependent upon the pH and buffer capacity of the sample at the
8.5 Hexadecane—98 % minimum purity.
time of collection. If the amount of acid required is not known,
8.6 Soybean Oil—CAS No. 8001-22-7, analytical standard.
make the pH measurement on a separate sample that will not be
8.7 Mineral Oil—CAS No. 8042-47-5, 98 % minimum
analyzed. Introduction of pH paper to an actual sample or
purity.
sample cap can remove some oil from the sample. To more
accurately calculate the final TOG or TPH concentration, or
8.8 Silica Gel, anhydrous, 75 μm to 150 μm, high-purity
both, of the extract, the volume of acid added to each sample
grade 923—Dry at 200 °C to 250 °C for 24 h minimum and
can be recorded, then subtracted from the final measured
store in a desiccator or tightly sealed container. Determine the
sample volume.
n-hexane soluble material content of the silica gel by extracting
10 g of silica gel with 25 mL of n-hexane and collect the elute
NOTE 2—If the sample is to be shipped by commercial carrier, see 40
in a flask. Filter and analyze the elute by IR. The n-hexane
CFR Part 136, Table II Footnote 3 (if HCl is used) or 49 CFR part 172 (if
H SO is used) for pH limits.
soluble material must be less than 5 mg/L.
2 4
9.4 For those circumstances requiring the collection of
8.9 Sodium Sulfate (Na SO ), ACS, granular anhydrous—
2 4
multiple aliquots of one sample, each aliquot is to be collected
Dry at 200 °C to 250 °C for 24 h minimum and store in a
in either of the following ways: (1) collect simultaneously in
tightly sealed container until use.
parallel, if possible, or (2) collect as grab samples in rapid
NOTE 1—Powdered sodium sulfate should not be used because water
succession, filling ⁄3 of each container at a time and continuing
can cause it to solidify.
until all containers are full, consistent with 9.1.
8.10 Sulfuric Acid (1 + 1)—Slowly and carefully add 1
volume of sulfuric acid (H SO , sp gr 1.84 g/cm ) to 1 volume
2 4
10. Preparation of Calibration and Spiking Solutions
of water, stirring and cooling the solution during the addition
10.1 Oil Types:
(optional HCl replacement).
10.1.1 Mineral Oil—Used for calibrating the apparatus for
8.11 Hydrochloric Acid, ACS, 1 + 1—Mix equal volumes of
TPH.
concentrated HCl and water.
10.1.2 50:50 Mix of Hexadecane/Soybean Oil—Used for
8.12 Sodium Chloride (NaCl), crystalline, ACS—for use in
calibrating the apparatus for TOG.
breaking emulsions, if needed. Wet thoroughly with n-hexane
10.1.3 Known Oil—In a few cases, the composition of the
before using.
oil and grease in a sample will be known. In such cases, it is
possible to develop a calibration with the known target oil as
9. Sampling
long as all other steps in this test method are followed.
However, for such calibrations it is not possible to develop
9.1 Collect the sample in accordance with the principles
reproducibility statements and the repeatability statement of
described in Practice D3370, using a glass bottle equipped with
this test method will not be valid.
a screw cap having a fluoropolymer liner. Pre-rinse the sample
bottle and cap with the n-hexane prior to sample collection. Do
10.2 Calibration Mixtures:
not rinse the sample bottle with the sample to be analyzed. Fill 10.2.1 Calibration Stock Solution—Weigh 200 mg 6 2 mg
bottle with a known amount of sample (100 mL to 250 mL),
of oil into a 100-mL volumetric flask and fill to the mark with
larger sample sizes may be collected if necessary. If the n-hexane. Mix well. The resulting concentration is 2000 mg/L.
extraction is to be done in the sample bottle, leave enough
This solution will be termed “stock solution.”
headspace for the amount of n-hexane required for extraction,
10.2.2 Using volumetric pipettes, transfer various amounts
else keep the headspace at a minimum. Do not allow the
of stock solution into volumetric flasks and fill to the mark with
sample to overflow the bottle during collection. Preventing
n-hexane. The equation for calculating the calibration of the
overflow can be impossible in some sampling situations,
standard is as follows:
however, measures should be taken to minimize overflow at all
C 5 C × V ⁄ V (1)
std stock t f
times.
where:
9.2 Use the entire sample because removing a portion would
C = final concentration of the standard in mg/L,
std
not apportion the oil and grease that adheres to the bottle
C = concentration of the stock solution in mg/L,
stock
surfaces. The high probability that extractable matter can
V = volume of stock solution transferred in mL, and
t
adhere to sampling equipment and result in measurements that
D8478 − 23
11.4 Calibration:
V = final volume of the calibration solution in mL.
f
11.4.1 Equilibrate the instrument and all samples to the
10.2.2.1 Calibration Solution A—Place 0.5 mL of stock
temperature of the operating environment (15 °C to 27 °C)
solution in a 10-mL volumetric flask and fill to the mark with
prior to analysis.
n-hexane. Calibration Solution A = 100 mg/L, equivalent to
11.4.2 Allow the instrument to warm up for the period of
10 mg ⁄L TOG or TPH in a 150-mL water sample extracted into
time recommended by the manufacturer before attempting a
a 15-mL volume of n-hexane.
calibration.
10.2.2.2 Calibration Solution B—Place 1.5 mL of stock
11.4.3 Using a level, make sure the HATR sample plate and
solution in a 10-mL volumetric flask and fill to the mark with
crystal are level. Since the method requires n-hexane to be
n-hexane. Calibration Solution B = 300 mg/L, equivalent to
evaporated off, only a thin film of oil is measured on the
30 mg ⁄L TOG or TPH in a 150-mL water sample extracted into
instrument.
a 15-mL volume of n-hexane.
11.4.4 Clean the HATR crystal of any residual oil or other
10.2.2.3 Calibration Solution C—Place 2.5 mL of stock
contamination by applying about 1 mL of n-hexane to the
solution in a 10-mL volumetric flask and fill to the mark with
crystal and wiping across the crystal in one direction with a
n-hexane. Calibration Solution C = 500 mg/L, equivalent to
disposable wipe. Avoid rubbing back and forth since this can
50 mg ⁄L TOG or TPH in a 150-mL water sample extracted into
re-contaminate the crystal. Repeat the cleaning of the crystal
a 15-mL volume of n-hexane.
with isopropyl alcohol. Follow the instrument manufacturer’s
10.2.2.4 Calibration Solution D—Place 5.0 mL of stock
recommendation for determining crystal cleanliness.
solution in a 10-mL volumetric flask and fill to the mark with
11.4.5 Using a 100 μL glass syringe, deposit a specific
n-hexane. Calibration Solution D = 1000 mg/L, equivalent to
amount of n-hexane on the crystal based on the instrument
100 mg/L TOG or TPH in a 150-mL water sample extracted
manufacturer’s recommendation. It is crucial to use the same
into a 15-mL volume of n-hexane.
amount of volume for every measurement.
10.2.2.5 Calibration Solution E—Place 7.5 mL of stock
11.4.6 Allow enough time for the n-hexane to evaporate.
solution in a 10-mL volumetric flask and fill to the mark with
The minimum evaporation time is 3 min and the maximum
n-hexane. Calibration Solution E = 1500 mg/L, equivalent to
evaporation time is 5 min. If the n-hexane does not evaporate
150 mg/L TOG or TPH in a 150-mL water sample extracted
completely before taking a baseline detector response, the
into a 15-mL volume of n-hexane.
results will have a negative bias.
10.2.2.6 Calibration Solution F—Place 10.0 mL of stock
11.4.7 Obtain a baseline detector response (zero) according
solution in a 10-mL volumetric flask. Calibration Solution F =
to the manufacturer’s instructions. A zero should be obtained
2000 mg/L, equivalent to 200 mg/L TOG or TPH in a 150-mL
before the first use and at least once every 60 min the
water sample extracted into a 15-mL volume of n-hexane.
instrument is in use.
10.3 TOG Precision and Recovery (TOG-PAR) Standard:
11.4.8 Clean the crystal according to 11.4.4.
10.3.1 Weigh in 45 mg 6 1 mg of a 50:50 mix of hexade-
11.4.9 Wash out the glass syringe with the first standard and
cane and soybean oil into sample bottle.
deposit a specific amount of standard on the crystal based on
10.3.2 Pour 900 mL 6 10 mL reagent water into the sample
the instrument manufacturer’s recommendation. It is crucial to
bottle in order to produce a TOG-PAR standard with approxi-
use the same amount of volume for every measurement.
mately 50 mg/L.
11.4.10 Allow enough time for the standard to evaporate.
10.4 TPH Precision and Recovery (TPH-PAR) Standard: The minimum evaporation time is 3 min and the maximum
10.4.1 Weigh in 45 mg 6 1 mg of mineral oil into sample
evaporation time is 5 min. If the standard does not evaporate
bottle. completely, the results will have a positive bias. If the
10.4.2 Pour 900 mL 6 10 mL reagent water into the sample
evaporation time is longer than 5 min, there can be an
bottle in order to produce a TPH-PAR standard with approxi- increased loss of volatile hydrocarbons causing a negative bias.
mately 50 mg/L.
All measurements (both calibration and sample measurements)
must use the same evaporation time.
11. Calibration and Standardization
11.4.11 Obtain an infrared detector response according to
11.1 Rely upon recommendations of the manufacturer of the
the manufacturer’s instructions and calculate the absorbance
-1 -1
analyzer because variations in design make it impractical to
value from 3.34 μm to 3.54 μm (2825 cm to 2994 cm ). The
offer specific instructions for this method. Also, in relation to
absorbance value may be calculated internally by the instru-
infrared filtometer operation, reference to scanning or running,
ment.
or both, should be interpreted to mean obtaining a reading or a
11.4.12 Clean the crystal according to 11.4.4.
-1 -1
plot from 3.34 μm to 3.54 μm (2825 cm to 2994 cm ).
11.4.13 Repeat 11.4.9 – 11.4.12 at least two more times for
the standard. Average the absorbance values recorded.
11.2 To ensure analytical values obtained using this test
11.4.14 Repeat 11.4.9 – 11.4.13 for the remaining standards.
method are valid and accurate within the confidence limits of
the test, the instrument manufacturer’s instructions and the
11.5 Calibration Curve—One of the following calibration
calibration procedure (11.4) must be followed when perform-
fits may be used in generating the calibration curve.
ing the test method.
11.5.1 Linear Calibration—A linear calibration may be used
11.3 Calibration Standards—Refer to 10.1 and 10.2 for if at least five calibration standards are included in the
calibration standard description. calibration. Two separate linear calibrations may be used for
D8478 − 23
the ranges of 50 mg ⁄L to 1000 mg/L (5 mg ⁄L to 100 mg ⁄L in for extraction, transfer the sample from the sample bottle to a
the water sample) and 1000 mg ⁄L to 2000 mg ⁄L (100 mg ⁄L to clean separatory funnel via a clean transfer funnel.
200 mg ⁄L in the water sample) as long as each calibration has 12.2.2 Add n-hexane at a proportion of 10:1 (sample to
at least five calibration standards. n-hexane) to the original sample volume and cap with the
original cap. If the sample has been transferred to a separatory
11.5.2 Quadratic Calibration—A quadratic calibration may
be used if at least six calibration standards are included in the funnel, shake the sample bottle to rinse all interior surfaces and
pour the n-hexane into the separatory funnel.
calibration.
12.2.3 Extract the sample by shaking vigorously for 2 min
11.5.3 Point-to-Point Calibration—A point-to-point calibra-
with periodic venting into a hood to release excess pressure.
tion may be used if the calibration using a quadratic equation
Vent the funnel slowly to prevent loss of sample.
is verified in accordance with 11.6. A point-to-point calibration
12.2.4 Allow the phases to separate.
requires at least six calibration standards.
NOTE 4—Certain types of samples, such as those containing a large
11.6 Calibration Verification:
amount of detergent, can form an emulsion during the extraction. If
11.6.1 Using the calibration constants determined in 11.5
emulsion forms between the phases and the emulsion is greater than
along with the absorbance values recorded in 11.4, calculate
one-third the volume of the extract layer, emulsion-breaking techniques
the predicted concentrations for all calibration standards. The
should be employed to complete the phase separation. The optimum
technique depends upon the sample, but may include stirring, filtration
error for any calibration standard shall not exceed the greater of
through glass wool, use of solvent phase separation paper, centrifugation,
3 ppm (30 ppm in n-hexane concentration) or 10 % relative of
use of an ultrasonic bath with ice, addition of NaCl, increasing the
the actual concentration of the standard. If one of the calibra-
temperature, lowering the pH, or other physical methods.
tion standards does not meet the error limit, this point must be
12.2.5 Place a filter paper in a filter funnel, add approxi-
reanalyzed. If the point still does not meet the error limit, it
mately 1 g of Na SO , rinse with a small portion of the extract
2 4
may be excluded but still must contain the minimal points
and discard the rinsate.
dictated in 11.5. The high or low point of the calibration may
be excluded but the reporting range must be modified to reflect NOTE 5—Use of the sodium sulfate is necessary to prevent water from
interfering in the determination. If the sodium sulfate cakes when
this change. If two points must be excluded, calibration must
contacted with the extract, flush once with 2 mL of n-hexane into the
be repeated, an
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