ASTM E1645-21

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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: E1645 − 20a E1645 − 21
Standard Practice for
Preparation of Dried Paint Samples by Hotplate or
Microwave Digestion for Subsequent Lead Analysis
This standard is issued under the fixed designation E1645; 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 practice covers the sample preparation procedures for paint samples that are collected during the assessment, management
or control of lead hazards.
1.2 This practice describes the digestion procedures using a hot plate or microwave oven or apparatus for paint samples that are
to be analyzed for lead content.
1.3 This practice covers the general considerations for quantitative sample extraction for total recoverable lead in dried paint
samples (either bulk paint or paint powder) using hot plate or microwave heating techniques, or both.
1.4 This practice contains notes that are explanatory and not part of the mandatory requirements of the standard.
1.5 This practice is based on NIOSH Methods 7082 and 7105, and on an EPA standard operating procedure for lead in paint.
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. For specific warning statements, see 6.1.2, 6.1.2.1, 6.1.2.2, 6.3.2.4, 7.2.18.2.1, and 7.2.28.2.2.
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.
2. Referenced Documents
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
E288 Specification for Laboratory Glass Volumetric Flasks
This practice is under the jurisdiction of ASTM Committee D22 on Air Quality and is the direct responsibility of Subcommittee D22.12 on Sampling and Analysis of
Lead for Exposure and Risk Assessment.
Current edition approved Nov. 1, 2020Sept. 1, 2021. Published December 2020October 2021. Originally approved in 1994. Last previous edition approved in 2020 as
E1645 – 20.E1645 – 20a. DOI: 10.1520/E1645-20A.10.1520/E1645-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. 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
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E969 Specification for Glass Volumetric (Transfer) Pipets
E1605 Terminology Relating to Lead in Buildings
E1729 Practice for Field Collection of Dried Paint Samples for Subsequent Lead Determination
2.2 ISO Documents:
ISO Guide 30 Reference materials — Selected terms and definitions
ISO 1042 Laboratory glassware — One-mark volumetric flasks
ISO 8655 Piston-operated volumetric apparatus — Part 1: Terminology, general requirements and user recommendations
2.3 Other Documents:
NTIS No. PB92–114172 Standard Operating Procedures for Lead in Paint by Hotplate- or Microwave-based Acid Digestions
and Atomic Absorption or Inductively Coupled Plasma Emission Spectrometry
NMAM 7082 and 7105 NIOSH Manual of Analytical Methods, 4th ed.
3. Terminology
3.1 Definitions—For definitions of terms relating to the preparation of dried paint samples that are not given here, refer to
Terminologies D1129, D1356, or E1605.
3.1.1 batch, n—a group of field or quality control samples that are processed together using the same reagents and equipment.
3.1.2 digestate, n—an acidified aqueous solution that results from digestion of the sample.
3.1.3 digestion, n—the sample preparation process that solubilizes (extracts) targeted analytes present in the sample, and results
in an acidified aqueous solution called the digestate.
3.1.4 extraction, n—the dissolution of target analytes from a solid matrix into a liquid form. During sample digestion, target
analytes are extracted (solubilized) into an acid solution.
3.1.5 method blank, n—a sample, devoid of analyte, that is analyzed to determine its contribution to the total blank (background)
reading.
3.1.6 non-spiked sample, n—a sample, devoid of analyte, that is targeted for addition of analyte but is not fortified with all target
analytes prior to sample preparation.
3.1.6.1 Discussion—
Analysis results for this sample are used to correct for background levels in the blank medium that is used for spiked and spiked
duplicate samples.
3.1.7 reagent blank, n—a digestate that reflects the maximum treatment given any one sample within a batch of samples, except
that it has no sample placed initially into the digestion vessel. (The same reagents and processing conditions that are applied to
field samples within a batch are also applied to the reagent blank.)
3.1.7.1 Discussion—
Analysis results from this sample provide information on the level of potential contamination resulting from only laboratory
sources that are experienced by samples processed within the batch.
3.1.8 reference material (certified reference material) (CRM), n—reference material accompanied by a certificate, one or more of
whose property values are certified by a procedure which establishes its traceability to an accurate realization of the unit in which
the property values are expressed; each certified value is accomplished by an uncertainty at a stated level of confidence. ISO Guide
3.1.9 sample set, n—a group of samples (one or more).
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
U.S. EPA, Research Triangle Park, NC (1991). Available from National Technical Information Service (NTIS), 5301 Shawnee Rd., Alexandria, VA 22312,
http://www.ntis.gov.
P.M. Eller, and M.E. Cassinelli, Eds., National Institute for Occupational Safety & Health, Cincinnati, OH (1994). Available from NIOSH Publications, 1150 Tusculum
Ave, Cincinnati, OH 45226, Mail Stop C14, http://www.cdc.gov/niosh.
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3.1.10 spiked sample or spiked duplicate sample, n—a blank medium that contains no purposely added analyte to which a known
amount of analyte is added before preparation.
3.1.10.1 Discussion—
Analysis results for these samples are used to provide information on the precision and accuracy of the overall process.
4. Summary of Practice
4.1 Lead in dried paint samples (chips, powder, and so forth) is solubilized (extracted) by digestion with nitric acid and hydrogen
peroxide facilitated by heat, or by a mixture of nitric acid and hydrochloric acid facilitated by microwave energy. (It is assumed
that the paint samples were collected in accordance with Practice E1729; however, this practice can be used for any collected paint
sample.) The lead content of the digested sample is then in a form ready for measurement.
5. Significance and Use
5.1 Paint in buildings and related structures needs to be monitored for lead content in order to determine the potential lead hazard.
Hence, effective and efficient methods are required for the preparation of paint samples that may contain lead.
5.2 This practice may be used for the digestion of paint samples that are collected during various lead-hazard control and risk
assessment activities associated with lead abatement in and around buildings and related structures. This practice is also suitable
for the digestion of paint samples collected from locations such as commercial buildings.
5.3 This practice may be used to prepare samples that have been obtained in order to ensure compliance with laws that govern
lead content in paints.
5.4 This practice may be used to prepare samples that have been collected for risk assessment purposes.
5.5 This practice is intended for use with paint samples that are prepared for subsequent analysis by quantitative analytical
methods.
6. Apparatus
6.1 Heating Equipment:
6.1.1 Electric Hot Plate—suitable for operation at surface temperatures up to at least 140 °C. A temperature of at least 100 °C,
as measured by a thermometer placed inside a borosilicate glass container (on the hot plate) filled with digestion solution, should
be attainable. (See Note 1.)
NOTE 1—Provided that the hot plate is capable of handling the extra heating required, use of a 12 to 25-mm (approximately 0.5 to 1-in.) thick aluminum
plate placed on the burner head can help reduce the presence of hot spots common to electric hot plates.
6.1.2 Microwave Extraction Apparatus:
Warning—Ensure that manufacturer’s safety recommendations are followed.
NOTE 2—The procedure described is for microwave digestion systems with a temperature control system. Microwave digestion systems that are equipped
only with a pressure control system or lower pressure vessels, or both, may be used, provided that a prior assessment of the dissolution efficiency is carried
out.
6.1.2.1 Microwave Digestion System—designed for closed vessel digestion, with power output regulation, fitted with a temperature
control system capable of sensing the temperature to within 62 °C, and automatically adjusting the microwave power output
within 2 s. The microwave cavity shall be resistant to chemical attack, and equipped with exhaust ventilation for acid vapor
protection of the unit and operator. All electronics shall be protected against corrosion to ensure safe operation. Safety interlocks,
to shut off magnetron power output, shall be contained within the oven door opening mechanism.
Warning—Domestic (kitchen) microwave ovens shall not be used, since there are very significant hazards associated with their
use for the procedure described in this standard. For example, acid vapors released into the cavity can corrode safety devices that
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prevent the magnetron from shutting off when the door is opened, potentially exposing the operator to microwave energy. Also,
the fumes generated can be extremely hazardous.
NOTE 3—A pressure control system is also very useful, since it provides a safeguard against the possibility of sample loss due to excessive pressure
buildup and partial venting of the sample vessels.
6.1.2.2 Lined Sample Vessels—closed, designed for carrying out microwave digestions, capable of withstanding a temperature of
at least 180 °C and with an internal volume of at least 50 mL. The vessels must be transparent to microwave energy, and vessel
liners shall be chemically inert. The vessels must be capable of withstanding high internal pressures (up to at least 3000 kPa) and
temperatures (up to at least 180 °C). Vessels shall also be equipped with a safety relief valve or disc that will prevent vessel rupture
or ejection of the vessel cap. Such vessels consist of an inner liner and cover made of a microwave transparent and chemically
resistant material (usually a fluorocarbon polymer such as tetra-fluoromethoxil polymer (TFM), which contains and isolates the
sample solution from a high strength, outer pressure structure. Other types of sample vessels designed to operate at equivalent or
higher temperatures or pressures, or both, may be used.
Warning—For closed vessel designs, the material from which the outer vessels are made is usually not as chemically inert as
the liner material. Since the outer vessels provide the strength required to withstand the high pressures within the inner liners, they
must be inspected regularly to check for any chemical or physical degradation.
6.2 Glassware and Supplies:
6.2.1 Apparatus-Hot Plate Digestion:
6.2.1.1 Borosilicate glass beakers, 125-mL or 50-mL with watchglass covers,
6.2.1.2 Borosilicate volumetric flasks meeting Specification E288 or conforming to ISO 1042, 100-mL and 200-mL,
6.2.1.3 Borosilicate volumetric pipets meeting Specification E969 or piston-operated pipets conforming to ISO 8655, volume as
needed,
6.2.1.4 Linear polyethylene bottles with caps, 100-mL,
6.2.1.5 Analytical balance, accurate to 60.1 mg,
6.2.1.6 Glass funnels,
6.2.1.7 Filter paper, and
6.2.1.8 Weighing Paper or Weighing Boat.
6.2.2 Apparatus-Microwave Digestion:
6.2.2.1 Centrifuge, with 30 mL polysulfone centrifuge tubes and polypropylene screw closure,
6.2.2.2 Borosilicate volumetric pipets meeting Specification E969 or piston-operated pipets conforming to ISO 8655, volume as
needed,
6.2.2.3 Mechanical shaker, and
6.2.2.4 Analytical balance, accurate to 60.1 mg.
6.2.3 Mortar and pestle (porcelain or agate), shatter box, or mixer mill.
6.2.4 Plastic gloves, powderless.
6.2.5 Thermometers, red alcohol, that cover a range from 0 °C to 110 °C.
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6.3 Reagents:
6.3.1 Reagents-Hot Plate Digestion:
6.3.1.1 Concentrated nitric acid, ACS reagent grade or spectrographic grade 16.0 M HNO ,
6.3.1.2 Nitric acid, mass fraction 10 %: Add 100 mL concentrated HNO to 500 mL ASTM Type I water (see Water, 6.3.1.4.
References to ASTM Type I water shall mean reagent water as defined by Type I of Specification D1193). (ASTM Type I water:
minimum resistivity of 16.7 megohm·cm, or equivalent.) Dilute to 1 L with ASTM Type I water,
6.3.1.3 Hydrogen peroxide, mass fraction 30 % H O ; ACS reagent grade, and
2 2
6.3.1.4 ASTM Type I water.
6.3.2 Reagents-Microwave Digestion:
6.3.2.1 Concentrated nitric acid, ACS reagent grade or spectrographic grade 16.0 M HNO ,
6.3.2.2 Concentrated hydrochloric acid, ACS reagent grade 12.3 M HCl,
6.3.2.3 ASTM Type I water, and
6.3.2.4 Extraction Solution—In a 1-L volumetric flask, combine the following in order and mix well: 500 mL ASTM Type I water,
60 mL concentrated HNO and 180 mL concentrated HCl. Allow to cool to room temperature and dilute to 1 L with ASTM Type
I water. (Warning—Nitric and hydrochloric acid mists and vapors are toxic. Prepare in a well-ventilated fume hood.)
7. Equipment Preparation
7.1 Wash glassware and plastic equipment with laboratory detergent, rinse with tap water, soak for at least 4 hours in volume
fraction 35 % nitric acid and water, rinse three times with ASTM Type I Water, and allow
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