ASTM D5012-20

Standard Practice for Preparation of Materials Used for the Collection and Preservation of Atmospheric Wet Deposition

SIGNIFICANCE AND USE
4.1 Some chemical constituents of AWD are not stable and must be preserved before chemical analysis. Without sample preservation, it is possible that analytes can be lost through decomposition or sorption to the storage bottles.  
4.2 Contamination of AWD samples can occur during both sample preservation and sample storage. Proper selection and cleaning of sampling containers are required to reduce the possibility of contamination of AWD samples.  
4.3 The natural sponge and talc-free plastic gloves used in the following procedures should be recognized as potential sources of contamination. Individual experience should be used to select products that minimize contamination.
SCOPE
1.1 This practice presents recommendations for the cleaning of plastic or glass materials used for collection of atmospheric wet deposition (AWD). This practice also presents recommendations for the preservation of samples collected for chemical analysis.  
1.2 The materials used to collect AWD for the analysis of its inorganic constituents and trace elements should be plastic. High density polyethylene (HDPE) is most widely used and is acceptable for most samples including samples for the determination of the anions of acetic, citric, and formic acids. Borosilicate glass is a collection alternative for the determination of the anions from acetic, citric, and formic acid; it is recommended for samples for the determination of other organic compounds.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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.  
1.5 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: 31-Aug-2020
• ICS: 07.060 - Geology. Meteorology. Hydrology
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.03 - Ambient Atmospheres and Source Emissions

Relations

• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D1356-20a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Sep-2020
• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D1356-20 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Mar-2020
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D1695-07(2019) - Standard Terminology of Cellulose and Cellulose Derivatives
• Effective Date: 01-Dec-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D883-17 - Standard Terminology Relating to Plastics
• Effective Date: 15-Aug-2017
• Refers: ASTM D1356-15a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Oct-2015
• Refers: ASTM D1356-15 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Jul-2015

Overview

ASTM D5012-20: Standard Practice for Preparation of Materials Used for the Collection and Preservation of Atmospheric Wet Deposition provides essential guidelines to ensure the integrity of samples collected from precipitation events, including rain, snow, and other forms of atmospheric wet deposition (AWD). Atmospheric wet deposition analysis is key for understanding environmental pollution, acid rain, and atmospheric chemistry. The standard details the proper selection, cleaning, and preparation of containers and materials used to collect, store, and preserve AWD samples before chemical analysis.

Compliance with ASTM D5012-20 assures minimal sample contamination and analyte loss, supporting accurate, reproducible results in environmental monitoring and research.

Key Topics

• Sample Preservation: Preserving chemical species in AWD samples is critical because certain analytes are unstable and can decompose, volatilize, or adsorb onto container surfaces if not properly managed. The standard outlines preservation techniques, such as refrigeration, acidification, and use of preservatives, depending on the target analytes.
• Sample Container Selection and Preparation: The document provides criteria for choosing appropriate collection and storage materials, emphasizing the use of high-density polyethylene (HDPE) and borosilicate glass for different analytical needs. Thorough cleaning and preconditioning processes are detailed to avoid sample contamination.
• Contamination Prevention: Procedures for cleaning buckets, bottles, and associated equipment are specified. The standard highlights potential sources of contamination, such as natural sponges and gloves, and recommends techniques to minimize risks.
• Handling and Storage: Guidance is provided for handling AWD samples to minimize exposure to atmospheric contaminants and biological activity. The preparation and packaging of cleaned materials are also addressed.
• Trace Metals and Organic Compounds: Specialized container materials and cleaning steps are prescribed for trace metals (including mercury) and organic acids due to their susceptibility to contamination and sample loss.

Applications

ASTM D5012-20 is widely applied in:

• Environmental Monitoring: National and regional atmospheric deposition networks use this standard to ensure high-quality precipitation chemistry data for tracking acid rain, nutrient deposition, and pollution trends.
• Academic Research: Universities and research institutions conducting studies on atmospheric chemistry, hydrology, and ecosystem impacts utilize these practices for reproducible, accurate sampling.
• Regulatory Compliance: Laboratories performing wet deposition monitoring for government programs or environmental compliance employ these standard procedures to meet quality assurance requirements.
• Industrial and Consulting Services: Environmental consultants and analytical laboratories rely on ASTM D5012-20 to guarantee the reliability of sample collection and preservation in contract monitoring projects.

Related Standards

For comprehensive precipitation and water sampling expertise, refer to these related ASTM standards:

• ASTM D883: Terminology Relating to Plastics - definitions related to plastic materials.
• ASTM D1125: Test Methods for Electrical Conductivity and Resistivity of Water - procedures relevant for bottle rinsing validation.
• ASTM D1193: Specification for Reagent Water - requirements for water purity.
• ASTM D1356: Terminology Relating to Sampling and Analysis of Atmospheres.
• ASTM D2914: Test Methods for Sulfur Dioxide Content of the Atmosphere.
• ASTM D4453: Practice for Handling of High Purity Water Samples.

These documents complement ASTM D5012-20, providing terminology, test methods, and additional sample handling recommendations essential for high-integrity AWD sample collection.

Practical Value

Adopting ASTM D5012-20 ensures:

• Reliable collection and preservation of atmospheric wet deposition samples.
• Minimized risk of analyte loss and sample contamination.
• Consistent procedures supporting data comparability across monitoring networks and laboratories.
• Adherence to internationally recognized best practices, aiding in regulatory compliance and scientific publication.

By following ASTM D5012-20, organizations and researchers ensure the highest confidence in their atmospheric wet deposition analyses, contributing to critical environmental monitoring and decision-making processes.

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: D5012 − 20
Standard Practice for
Preparation of Materials Used for the Collection and
Preservation of Atmospheric Wet Deposition
This standard is issued under the fixed designation D5012; 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 D1125 Test Methods for Electrical Conductivity and Resis-
tivity of Water
1.1 Thispracticepresentsrecommendationsforthecleaning
D1129 Terminology Relating to Water
of plastic or glass materials used for collection of atmospheric
D1193 Specification for Reagent Water
wet deposition (AWD). This practice also presents recommen-
D1356 Terminology Relating to Sampling and Analysis of
dations for the preservation of samples collected for chemical
Atmospheres
analysis.
D1695 Terminology of Cellulose and Cellulose Derivatives
1.2 ThematerialsusedtocollectAWDfortheanalysisofits
inorganic constituents and trace elements should be plastic.
3. Terminology
High density polyethylene (HDPE) is most widely used and is
3.1 Definitions:
acceptable for most samples including samples for the deter-
3.1.1 For definitions of terms used in this practice, refer to
mination of the anions of acetic, citric, and formic acids.
Terminology D1129.
Borosilicate glass is a collection alternative for the determina-
3.1.2 For definition of plastic, refer to Terminology D1695
tion of the anions from acetic, citric, and formic acid; it is
and Terminology D883.
recommended for samples for the determination of other
3.1.3 FordefinitionofAWD(precipitation,meteorological),
organic compounds.
refer to Terminology D1356.
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
4. Significance and Use
standard.
4.1 Some chemical constituents of AWD are not stable and
1.4 This standard does not purport to address all of the
must be preserved before chemical analysis. Without sample
safety concerns, if any, associated with its use. It is the
preservation, it is possible that analytes can be lost through
responsibility of the user of this standard to establish appro-
decomposition or sorption to the storage bottles.
priate safety, health, and environmental practices and deter-
4.2 Contamination of AWD samples can occur during both
mine the applicability of regulatory limitations prior to use.
sample preservation and sample storage. Proper selection and
1.5 This international standard was developed in accor-
cleaning of sampling containers are required to reduce the
dance with internationally recognized principles on standard-
possibility of contamination of AWD samples.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 4.3 The natural sponge and talc-free plastic gloves used in
mendations issued by the World Trade Organization Technical
the following procedures should be recognized as potential
Barriers to Trade (TBT) Committee. sources of contamination. Individual experience should be
used to select products that minimize contamination.
2. Referenced Documents
2.1 ASTM Standards:
5. Apparatus
D883 Terminology Relating to Plastics
5.1 Instruments shall be selected in accordance with an
applicable test method given in Test Methods D1125.
This practice is under the jurisdiction ofASTM Committee D22 on Air Quality
and is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres
5.2 The conductivity cell shall be pipet or dip type with a
and Source Emissions.
cell constant (K) of 0.1.
Current edition approved Sept. 1, 2020. Published September 2020. Originally
approved in 1989. Last previous edition approved in 2013 as D5012 – 01 (2013).
6. Reagents and Materials
DOI: 10.1520/D5012-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.1 Purity of Reagents—Reagent grade acids and other
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
chemicals shall be used to reduce the risk of contaminating the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. AWD samples. Unless otherwise indicated, it is intended that
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5012 − 20
TABLE 1 Preservation of AWD Samples Collected for Inorganic Cation and Anion Determinations
Preservation Technique Species Determined Remarks Reference
No preservation All inorganic cations and Rapid analysis is required after collection because ion concentrations may change in (3-7)
anions samples. Ammonium, nitrate, and ortho-phosphate concentrations may be reduced
in samples that are biologically active. Cation and trace metal concentrations may
be reduced by sorption onto container surfaces.
Refrigerate 4°C All inorganic cations and an- Chilling may reduce the loss of ammonium, nitrate, and ortho-phosphate in samples (8-10)
ions that are biologically active. Samples must be allowed to come to ambient tempera-
ture (23–27°C) before performing pH and specific conductance determinations.
Specific conductance and pH determinations should be performed on-site as soon
as possible after sample collection.
2+ 2+ + +
HNO pH#2Ca ,Mg ,Na ,K Samples must first be filtered, or acid addition may dissolve particles in the AWD (4,5)
samples (see 7.4.1). Acid addition will interfere with anion determination, so a
separate aliquot will be needed for other ion determinations.
HCl, 5 mL/L All dissolved Hg and total Hg Samples for dissolved Hg are filtered through 0.45 µm capsule filter. Samples col- (1,2)
lected directly into specially cleaned, pretested, fluoropolymer bottle.
Filtration All inorganic cations and an- pH and specific conductance determinations may be affected by filtration. Care must (11)
ions be taken to minimize the possibility of sample contamination during filtration.
all reagents conform to the specifications of the Committee on 7.2 Samples Collected for Inorganic Cation and Anion
Analytical Reagents of the American Chemical Society where Determinations:
such specifications are available.
7.2.1 Samples collected for pH, specific conductance,
calcium, magnesium, potassium, sodium, chloride, fluoride,
6.2 Nitric acid, ultra pure.
andsulfateanalysisareoftenonlyplacedinpre-cleanedplastic
6.3 Nitric acid (1+9), dilute 1 volume concentrated nitric
containers (see Section 8) before analysis. If there is a delay
acid with 9 volumes of water.
between time of collection and time of analysis, a preservation
6.4 Chloroform, high performance liquid chromatography
technique may eliminate or moderate chemical and biological
reagent.
changes in the AWD samples. Table 1 summarizes the recom-
mended sample preservation techniques for AWD samples.
6.5 Hydrochloric acid, pretested for total and methyl mer-
cury.
7.3 Samples Collected for Organic Acids:
6.6 Purity of Water—Unless otherwise indicated, references 7.3.1 Samples collected for the analysis of acetate, citrate,
to water shall be understood to mean reagent water as defined formate, and other low molecular weight organic acid anions
by Type I of Specification D1193.AWD samples collected for (C -C ) should be preserved within minutes after collection.
1 12
organic analysis may require Type II (distilled) reagent water. OrganicacidshavebeendeterminedinAWDsamplescollected
from locations around the world (12-18).These compounds (in
7. Sample Preservation
particular formic and acetic acids) can constitute from a small
fraction to mostly all of the free acidity in AWD samples.
7.1 Interactionbetweenthesampleandtheatmospheremust
Because these acids are unstable in AWD samples, samples
be minimized. The sample container should be sealed as soon
must be analyzed within hours after collection or else a
as possible after collection or sub-sampling.AWD samples can
preservation technique is required. Table 2 summarizes the
be easily contaminated because of the low concentration levels
recommended sample preservation techniques for AWD
oftheiranalytes.Tracemetals,andpossiblyotherionsinAWD
samples.
samples, can be lost through sorption with the bottle or
container in which they are stored.AWD samples may contain
7.4 Samples Collected for Trace Dissolved Metals:
biologically active microorganisms which could affect the
7.4.1 Samplescollectedfortracemetalsshouldbefilteredto
concentration of many analytes. Immediate analysis of AWD
remove insoluble particulate matter often found in AWD
samples is best and chemical preservation should be used only
samples unless an AWD particulate trace element analysis is
when the preservation is shown not to interfere with the
desired. Filter pore size should be ≤0.45 µm. Filter materials
analysis being performed. Samples collected for total and
may contain trace elements, and the filters should be precon-
methyl mercury determinations are to be collected directly into
ditioned before use by filtering 300 mL of water in order to
specially cleaned, pretested, fluoropolymer bottle(s) (1 and
leach soluble impurities on the filter and from the filtration
2).
apparatus itself (19).Any filters used forAWD samples should
betestedtodetermineifthefiltercauseslossesorgainsoftrace
elements to theAWD sample.Test the preconditioned filters by
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
filtering 50 mL of water and determine the analyte concentra-
Standard-Grade Reference Materials, American Chemical Society, Washington,
tions of interest in the filtrate.
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
7.4.2 Acidify the AWD sample with nitric acid to pH ≤2to
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
minimize container adsorption of trace metals. The highest
copeial Convention, Inc. (USPC), Rockville, MD.
purity acid available should be used. Most AWD samples are
The boldface numbers in parentheses refer to the list of references at the end of
this standard. poorly buffered and only small quantities of acid (about 1
D5012 − 20
TABLE 2 Preservation of AWD Samples Collected for Organic Acid Determinations
Preservation Technique Species Determined Remarks Reference
Chloroform Acetate, citrate, formate, Analysis is usually by ion-exclusion chromatography because chloroform may (14,15)
C –C interfere with capillary GC-MS analysis. This preservative is often coupled with
1 5
sample storage at 4°C. When chloroform treatment is combined with storage in
the dark at 4°C, samples are reportedly stable for 60 days. Final chloroform
concentration in the AWD sample must be 0.2 % by weight.
Freeze at − 20°C Short-chain dicarboxylic acids Analysis is by capillary gas chromatography or GC-MS. Sample must be completely (17)
C –C in the liquid state before sample is prepared for analysis. Maximum storage time
2 12
has not been reported.
Chill at 4°C Low molecular weight acids This is a minimum procedure for organic acid preservation. This preservation (18)
technique will not preserve acetate and formate longer than 3 days. Degradation
may occur in less than 3 days.
mL/L) are required to reduce the AWD sample to a pH ≤2. 8.2.8 Fillthebuckettoabout7.5cmdepthwithwater,cover
Samples acidified with an acid may not be used for the with a clean lid (see 8.2.11 and 8.2.12) and store overnight.
determination of pH and certain other analytes.
8.2.9 Measure the specific conductance of the water in the
7.4.3 Acidify the AWD sample with 5 mL/L of pretested bucket. Transfer a portion of the rinse water to a clean
HCl for dissolved mercury and total mercury.
measuring vessel and determine the specific conductance. If
the specific conductance is greater than 2 µS/cm (Test Methods
8. Sample Containers
D1125), repeat 8.2.4 – 8.2.8.
8.2.10 Shake the inverted bucket to remove any excess
8.1 ManyAWD sampling networks use samplers that utilize
water and place the bucket in a clean plastic bag, making sure
either a bucket or bottle that is an integral component of the
that only the interio
...

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: D5012 − 01 (Reapproved 2013) D5012 − 20
Standard GuidePractice for
Preparation of Materials Used for the Collection and
Preservation of Atmospheric Wet Deposition
This standard is issued under the fixed designation D5012; 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
1.1 This guidepractice presents recommendations for the cleaning of plastic or glass materials used for collection of atmospheric
wet deposition (AWD). This guidepractice also presents recommendations for the preservation of samples collected for chemical
analysis.
1.2 The materials used to collect AWD for the analysis of its inorganic constituents and trace elements should be plastic. High
density polyethylene (HDPE) is most widely used and is acceptable for most samples including samples for the determination of
the anions of acetic, citric, and formic acids. Borosilicate glass is a collection alternative for the determination of the anions from
acetic, citric, and formic acid; it is recommended for samples for the determination of other organic compounds.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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:
D883 Terminology Relating to Plastics
D1125 Test Methods for Electrical Conductivity and Resistivity of Water
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
D1695 Terminology of Cellulose and Cellulose Derivatives
D2914 Test Methods for Sulfur Dioxide Content of the Atmosphere (West-Gaeke Method)
D4453 Practice for Handling of High Purity Water Samples
This guidepractice is under the jurisdiction of ASTM Committee D22 on Air Quality and is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres
and Source Emissions.
Current edition approved Oct. 1, 2013Sept. 1, 2020. Published October 2013September 2020. Originally approved in 1989. Last previous edition approved in 20082013
as D5012 – 01 (2008).(2013). DOI: 10.1520/D5012-01R13.10.1520/D5012-20.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5012 − 20
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this guide,practice, refer to Terminology D1129.
3.1.2 For definition of plastic, refer to Terminology D1695 and Terminology D883.
3.1.3 For definition of AWD ( (precipitation, meteorological),precipitation, meteorological), refer to Terminology D1356.
4. Significance and Use
4.1 Some chemical constituents of AWD are not stable and must be preserved before chemical analysis. Without sample
preservation, it is possible that analytes can be lost through decomposition or sorption to the storage bottles.
4.2 Contamination of AWD samples can occur during both sample preservation and sample storage. Proper selection and cleaning
of sampling containers are required to reduce the possibility of contamination of AWD samples.
4.3 The natural sponge and talc-free plastic gloves used in the following procedures should be recognized as potential sources of
contamination. Individual experience should be used to select products that minimize contamination.
5. Apparatus
5.1 Instruments shall be selected in accordance with an applicable test method given in Test Methods D1125.
5.2 The conductivity cell shall be pipet or dip type with a cell constant (K) of 0.10.1.
TABLE 1 Preservation of AWD Samples Collected for Inorganic Cation and Anion Determinations
Preservation Technique Species Determined Remarks Reference
No preservation All inorganic cations and Rapid analysis is required after collection because ion concentrations may change in (3-7)
anions samples. Ammonium, nitrate, and ortho-phosphate concentrations may be reduced
in samples that are biologically active. Cation and trace metal concentrations may
be reduced by sorption onto container surfaces.
Refrigerate 4°C All inorganic cations and an- Chilling may reduce the loss of ammonium, nitrate, and ortho-phosphate in samples (8-10)
ions that are biologically active. Samples must be allowed to come to ambient tempera-
ture (23–27°C) before performing pH and specific conductance determinations.
Specific conductance and pH determinations should be performed on-site as soon
as possible after sample collection.
2+ 2+ + +
HNO pH # 2 Ca , Mg , Na , K Samples must first be filtered, or acid addition may dissolve particles in the AWD (4,5)
samples (see 7.4.1). Acid addition will interfere with anion determination, so a
separate aliquot will be needed for other ion determinations.
HCl, 5 mL/L All dissolved Hg and total Hg Samples for dissolved Hg are filtered through 0.45 μm capsule filter. Samples col- (1,2)
lected directly into specially cleaned, pretested, fluoropolymer bottle.
Filtration All inorganic cations and an- pH and specific conductance determinations may be affected by filtration. Care must (11)
ions be taken to minimize the possibility of sample contamination during filtration.
6. Reagents and Materials
6.1 Purity of Reagents—Reagent grade acids and other chemicals shall be used to reduce the risk of contaminating the AWD
samples. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical
Reagents of the American Chemical Society where such specifications are available.
6.2 Nitric acid, ultra pure.
6.3 Nitric acid (1+9)—Dilute (1+9), dilute 1 volume concentrated nitric acid with 9 volumes of water.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for
Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. PharmaceuticalPharmacopeial Convention, Inc.
(USPC), Rockville, MD.
D5012 − 20
TABLE 2 Preservation of AWD Samples Collected for Organic Acid Determinations
Preservation Technique Species Determined Remarks Reference
Chloroform Acetate, citrate, formate, Analysis is usually by ion-exclusion chromatography because chloroform may (14,15)
C –C interfere with capillary GC-MS analysis. This preservative is often coupled with
1 5
sample storage at 4°C. When chloroform treatment is combined with storage in
the dark at 4°C, samples are reportedly stable for 60 days. Final chloroform
concentration in the AWD sample must be 0.2 % by weight.
Freeze at − 20°C Short-chain dicarboxylic acids Analysis is by capillary gas chromatography or GC-MS. Sample must be completely (17)
C –C in the liquid state before sample is prepared for analysis. Maximum storage time
2 12
has not been reported.
Chill at 4°C Low molecular weight acids This is a minimum procedure for organic acid preservation. This preservation (18)
technique will not preserve acetate and formate longer than 3 days. Degradation
may occur in less than 3 days.
6.4 Chloroform, high performance liquid chromatography reagent.
6.5 Hydrochloric acid, pretested for total and methyl mercury.
6.6 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type
I of Specification D1193. AWD samples collected for organic analysis may require Type II (distilled) reagent water.
7. Sample Preservation
7.1 Interaction between the sample and the atmosphere must be minimized. The sample container should be sealed as soon as
possible after collection or sub-sampling. AWD samples can be easily contaminated because of the low concentration levels of their
analytes. Trace metals, and possibly other ions in AWD samples, can be lost through sorption with the bottle or container in which
they are stored. AWD samples may contain biologically active microorganisms which could affect the concentration of many
analytes. Immediate analysis of AWD samples is best and chemical preservation should be used only when the preservation is
shown not to interfere with the analysis being performed. Samples collected for total and methyl mercury determinations are to
be collected directly into specially cleaned, pretested, fluoropolymer bottle(s) (1 and 2).
7.2 Samples Collected for Inorganic Cation and Anion Determinations:
7.2.1 Samples collected for pH, specific conductance, calcium, magnesium, potassium, sodium, chloride, fluoride, and sulfate
analysis are often only placed in pre-cleaned plastic containers (see Section 8) before analysis. If there is a delay between time
of collection and time of analysis, a preservation technique may eliminate or moderate chemical and biological changes in the
AWD samples. Table 1 summarizes the recommended sample preservation techniques for AWD samples.
7.3 Samples Collected for Organic Acids:
7.3.1 Samples collected for the analysis of acetate, citrate, formate, and other low molecular weight organic acid anions (C -C )
1 12
should be preserved within minutes after collection. Organic acids have been determined in AWD samples collected from locations
around the world (12-18). These compounds (in particular formic and acetic acids) can constitute from a small fraction to mostly
all of the free acidity in AWD samples. Because these acids are unstable in AWD samples, samples must be analyzed within hours
after collection or else a preservation technique is required. Table 2 summarizes the recommended sample preservation techniques
for AWD samples.
7.4 Samples Collected for Trace Dissolved Metals:
7.4.1 Samples collected for trace metals should be filtered to remove insoluble particulate matter often found in AWD samples
unless an AWD particulate trace element analysis is desired. Filter pore size should be ≤0.45 μm. Filter materials may contain trace
elements, and the filters should be preconditioned before use by filtering 300 mL of water in order to leach soluble impurities on
the filter and from the filtration apparatus itself (19). Any filters used for AWD samples should be tested to determine if the filter
causes losses or gains of trace elements to the AWD sample. Test the preconditioned filters by filtering 50 mL of water and
determine the analyte concentrations of interest in the filtrate.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
D5012 − 20
7.4.2 Acidify the AWD sample with nitric acid to pH ≤2 to minimize container adsorption of trace metals. The highest purity acid
available should be used. Most AWD samples are poorly buffered and only small quantities of acid (about 1 mL/L) are required
to reduce the AWD sample to a pH ≤2. Samples acidified with an acid may not be used for the determination of pH and certain
other analytes.
7.4.3 Acidify the AWD sample with 5 mL/L of pretested HCl for dissolved mercury and total mercury.
8. Sample Containers
8.1 Many AWD sampling networks use samplers that utilize either a bucket or bottle that is an integral component of the AWD
samplers. These collection techniques allow “wet-only” samples to be obtained, meaning the bucket or bottle is only exposed to
the atmosphere during the precipitation event. The preparation or cleaning procedures described in Section 8 apply to the
automated AWD samplers that use buckets, and the sample storage bottles to which the AWD sample is tra
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