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October 2012 

CHAPTER THREE 

TABLE OF CONTENTS 

Section Page 

 

3.0 INTRODUCTION 1 

3.1 DEFINITIONS 1 

3.2 SAFETY 4 

3.3 SAMPLING CONSIDERATIONS 4 

3.4 SPECIAL CONSIDERATIONS FOR DETERMINING INORGANIC ANALYTES AT 

ULTRA-TRACE CONCENTRATION LEVELS 

6 

3.5 REAGENT PURITY 11 

3.6 SAMPLE DIGESTION METHODS 11 

3.7 METHODS FOR DETERMINATION OF INORGANIC ANALYTES 13 

3.8 REFERENCES FOR PREVIOUS SECTIONS AND THE TABLES AND FIGURES 16 

TABLE 

3-1 MATERIALS FOR USE IN SAMPLE COLLECTION FOR INORGANIC ANALYTE 

DETERMINATIONS 

19 

3-2 RECOMMENDED SAMPLE HOLDING TIMES, PRESERVATION, COLLECTION 

QUANTITIES, AND DIGESTION VOLUMES FOR SELECTED INORGANIC ANALYTE 

DETERMINATIONS IN AQUEOUS AND SOLID SAMPLES 

20 

3-3 EXAMPLES OF THE ANALYTICAL BLANK INFLUENCE ON ULTRA-TRACE 

ANALYSIS OF ELEMENTS IN GLASS 

22 

3-4 EXAMPLES OF LEAD CONCENTRATIONS IN AIR 22 

3-5 CLEANLINESS LEVELS IN INTERNATIONAL STANDARD ISO 14644-1 23 

3-6 PARTICULATE CONCENTRATIONS IN LABORATORY AIR 24

3-7 NON-CONTAMINATING MATERIALS AND FOR USE AS DIGESTION VESSELS AND 

SAMPLE CONTAINERS IN ULTRA-TRACE ANALYSIS 

24 

FIGURE 

3-1 COMPARISON OF CLEAN VERSUS CONVENTIONAL SAMPLING AND ANALYSIS 

TECHNIQUES USED IN THE ANALYSIS OF SOUTH TEXAS ESTUARY WATERS 

25 

3-2 COMPARISON OF PARTICLE COUNT ANALYSIS OF A CLEAN ROOM AND A 

STANDARD LABORATORY AT DUQUESNE UNIVERSITY IN PITTSBURGH, PA 

26 

3-3 PARTICLE SIZE COMPARISON CHART FOR COMMON PARTICULATES 27 

 

Appendix A SUMMARY OF UPDATES/CHANGES IN CHAPTER 3 28 
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CHAPTER THREE 

INORGANIC ANALYTES

 Prior to employing the methods in this chapter, analysts are advised to consult the 

disclaimer statement at the front of this manual and the information in Chapter Two for guidance 

on the allowed flexibility in the choice of apparatus, reagents, and supplies. In addition, unless 

specified in a regulation, the use of SW-846 methods is not mandatory in response to Federal 

testing requirements. The information contained in each procedure is provided by EPA as 

guidance to be used by the analyst and the regulated community in making judgments 

necessary to meet the data quality objectives or needs for the intended use of the data. 

For a summary of changes in Chapter Three, please see Appendix A at the end of this 

document. 

3.0 INTRODUCTION 

 This chapter provides guidance for the analysis of inorganic analytes in a variety of 

matrices. The analytical methods are written as specific steps in the overall analysis scheme -- 

sample handling and preservation, sample digestion or preparation, and sample analysis for 

specific inorganic components. From these methods, the analyst should assemble a total 

analytical protocol which is appropriate for the sample to be analyzed and for the information 

required. This introduction discusses the options available in general terms, provides 

background information on the analytical techniques, and highlights some of the considerations 

to be made when selecting a total analysis protocol. 

3.1 DEFINITIONS 

 The following terms are relevant for the determination of inorganic analytes: 

Calibration blank: The calibration blank is a sample of analyte-free media 

prepared with the same amounts of acids or other reagents as were the standards 

and samples that can be used along with prepared standards to calibrate the 

instrument. A calibration blank may also be used to verify absence of instrument 

contamination (e.g., initial calibration blank and continuing calibration blank). 

Calibration curve: The functional relationship between instrument response and 

target analyte concentration determined for a series of calibration standards. The 

calibration curve is obtained by plotting the instrument response versus 

concentration and performing a regression analysis of the data. 

Calibration standards: A series of solutions containing the target analyte at known 

and various concentrations used to calibrate the instrument response with respect 

to analyte concentration (i.e., preparation of the calibration curve). 

Continuing calibration verification (CCV): A solution containing a known 

concentration of analyte typically derived from the same source as the calibration 

standards. The CCV is used to assure calibration accuracy during each analysis 

run. It should be run for each analyte as described in the particular analytical 

method. At a minimum, it should be analyzed at the beginning of the run and after 
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the last analytical sample. The CCV concentration should be at or near the midrange levels of the calibration curve. 

Dissolved metals: The concentration of metals determined in an aqueous sample 

after the sample is filtered through a 0.45-μm filter (see Method 3005). 

Initial calibration verification (ICV) standard: A certified or independently-prepared 

solution from a source other than used for the calibration standards and used to 

verify the accuracy of the initial calibration. 

Instrument detection limit (IDL): Typically used in metals analysis to evaluate the 

instrument noise level and response changes over time for analytes of interest. 

IDLs in μg/L can be estimated as the mean of the blank results plus three times the 

standard deviation of 10 replicate analyses of the reagent blank solution. (Use zero 

for the mean if the mean is negative). Each measurement should be performed as 

though it were a separate calibration standard (i.e., each measurement must be 

followed by a rinse and/or any other procedure normally performed between the 

analysis of separate samples). IDLs should be determined at least once using new 

equipment, after major instrument maintenance such as changing the detector, 

and/or at a frequency designated by the project. An instrument log book should be 

kept with the dates and information pertaining to each IDL performed. 

Laboratory control sample (LCS): A volume of reagent water spiked with known 

concentrations of analytes and carried through the sample preparation and 

determinative procedure. It is used to monitor laboratory performance on analyte 

loss/recovery in a clean matrix. The LCS should be prepared from the same 

source as the calibration standards to remove potential error contribution from 

standards of different sources. An independently prepared LCS may also be 

obtained as or prepared from a certified reference solution or prepared from a 

certified reagent solid or from an alternate lot reagent solid relative to the 

calibration standards source if, for each analytical batch, at least one LCS is 

prepared from the same source as the calibration standards. In this way, if the 

recoveries of both the LCS and the matrix spike are outside the acceptance limits, 

the analyst will be able to determine whether the problem is due to calibration error 

or matrix interference. 

Linear range: In both inductively coupled plasma optical emission spectrometry 

(ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) analysis, 

the concentration range over which instrument response is linear. The linear range 

establishes the highest concentration that may be reported without diluting the 

sample. Following calibration, the laboratory may choose to analyze a standard at 

a higher concentration than the high standard in the calibration. The standard must 

recover within 10% of the true value, and if successful, establishes the linear 

range. The linear range standards must be analyzed in the same instrument run as 

the calibration they are associated with (i.e., on a daily basis) but may be analyzed 

anywhere within that run. If a linear range standard is not analyzed for any specific 

element, the highest standard in the calibration becomes the linear range. 

NOTE: Other standards exist that have alternative methods for determining the 

linear range (e.g., ISO 17025). Therefore, the method used to define and verify the 

linear range should meet the requirements of the project. 

Lower limit of quantitation (LLOQ): The lowest point of quantitation, or in most 

cases, the lowest point in the calibration curve, which is ideally less than or equal 
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to the desired regulatory action levels based on the stated project requirements. 

Laboratory-specific recovery limits should be established when the laboratory has 

determined sufficient data points exist. Individual methods specify recovery limits 

for use until the laboratory has sufficient data to determine acceptance limits 

statistically. 

Method blank: A volume of reagent water equal to that used for aqueous samples, 

or, otherwise, a clean, empty container, equivalent to that used for actual solid 

samples, processed through each sample preparation and determinative 

procedure. Analysis of a method blank is used to assess contamination from the 

laboratory environment, sample processing equipment, and/or reagents. 

Method of standard addition (MSA): An alternative calibration procedure employed 

when the instrument response of the analyte of interest is different in a particular 

matrix than when it is in reagent water. The procedure is generally reserved for 

analyzing complex matrices. The standard addition technique involves the addition 

of known amounts of the target analyte to each of a series of replicate sample 

aliquots. The final concentrations of the sample replicates should span the 

calibration range of the method. The analytical responses versus the standard 

addition concentration for each of the replicates is plotted. After performing a 

linear regression, the curve is extrapolated to the x-axis. The analyte 

concentration in the original unspiked sample is equal to the inverse of the xintercept. See Method 7000, for more information. 

Sample holding time: The storage time allowed between sample collection and 

sample analysis when the designated preservation and storage techniques are 

employed. Different times may be specified for holding field samples prior to 

extraction, digestion, or other such preparation procedures versus holding 

prepared samples (e.g. an extract or a digestate) prior to analysis. 

Sensitivity: The ability of an analytical technique or instrument to discriminate 

between small differences in analyte concentration (Reference 1). For metals 

analysis, the following methods are commonly employed to determine sensitivity. 

(a) Atomic absorption (AA): The concentration of metal, in mg/L, that 

produces a transmission of 1%. 

(b) Graphite furnace AA (GFAA): The mass of analyte required to give a 

response of 0.044 absorbance-seconds. 

(c) Inductively coupled plasma (ICP-OES or ICP-MS): Sensitivity is 

measured in terms of the instrument detection limits as defined elsewhere 

in the definitions. 

Spectral Interference Check solution (SIC): A solution containing both interfering 

and analyte elements of known concentration that can be used in ICP-OES and 

ICP-MS analysis to verify background and inter-element correction factors. 

Suspended metals: The concentration of metals determined in the portion of an 

aqueous sample that is retained by a 0.45-μm filter (Method 3005). 

 

Total acid soluble/recoverable metals: The concentration of metals determined in 

an unfiltered sample following digestion using hot mineral acid by Methods 3005, 

3010, 3015, 3020, 3050, or 3051. 
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October 2012 

NOTE: Methods 3010 and 3020 state they are used to determine “total metals”. 

However, because these methods do not use hydrofluoric acid, they are unable to 

break down silicates and have been defined here for the “total acid 

soluble/recoverable metals” fraction. 

Total metals: The concentration of metals determined in a sample following 

digestion by Method 3052. 

3.2 SAFETY 

 The methods in this chapter do not address all safety issues associated with their use. 

The laboratory is responsible for maintaining a safe work environment and a current awareness 

file of OSHA regulations regarding the safe handling of the chemicals specified in this method. 

A reference file of material safety data sheets (MSDSs) should be available to all personnel 

involved in these analyses. 

 The toxicity or carcinogenicity of each reagent used in these methods has not been 

precisely defined. However, each chemical compound should be treated as a potential health 

hazard. From this viewpoint, exposure to these chemicals should be reduced to the lowest 

possible level by whatever means available. The following additional references to laboratory 

safety are available: 

1. "Carcinogens - Working with Carcinogens," Department of Health, Education, and 

Welfare, Public Health Service, Centers for Disease Control, National Institute for 

Occupational Safety and Health, Publication No. 77-206, August 1977. 

2. "Handbook of Chemical Health and Safety," American Chemical Society, Oxford 

University Press, New York, 2001. 

3. "NIOSH Pocket Guide to Chemical Hazards," Department of Health and Human 

Services, Centers for Disease Control, National Institute for Occupational Safety and 

Health, Publication No. 2005-149, September 2005. 

4. "Occupational Safety and Health Standards," 29 CFR Part 1910, Occupational Safety 

and Health Administration, Department of Labor. 

5. "Safety in Academic Chemistry Laboratories," 7th Edition, Volumes 1 and 2, American 

Chemical Society, Committee on Chemical Safety, Washington, D.C., 2003. 

3.3 SAMPLING CONSIDERATIONS 

3.3.1 Sample Collection 

 The fundamental goal of all field sampling activities is to collect samples that are 

representative of the water, soil or waste from which they were collected. Thus, 

representative sampling may be considered to be the sampling analog to analytical 

accuracy. Of equal importance is sampling precision for ensuring consistency both within 

a single sampling event and between sampling events conducted over time. Sampling 

imprecision can be a significant source of measurement error. High quality field practices 

are, therefore, necessary for generating representative samples on a consistent basis. 

Sampling quality assurance includes the development of a quality assurance plan, data 
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quality objectives and the generation of field quality control samples including equipment 

rinsates, trip blanks and field duplicates. Regardless of the specific program needs, the 

documentation of all relevant field and sample information is the final essential component 

of a sampling event for providing evidence that proper procedures and quality assurance 

were performed during sample collection. Use of inadequate field procedures and 

documentation can jeopardize an entire sampling program despite adequate planning, 

analytical facilities, and personnel. 

 While advances in analytical sensitivity are continuing to be made that allow for 

quantification of environmental contaminants at ultra-trace levels (i.e., < 0.1 ppb), clean 

sampling techniques are consequently being devised and practiced in order to minimize or 

eliminate sources of contamination during the collection of samples intended for ultra-trace 

contaminant testing. Such clean sampling and analysis techniques are not generally 

needed or required under the RCRA program and are beyond the scope of this chapter. 

However, as an introduction to this topic, Sec. 3.4 provides a more detailed discussion on 

the special category and requirements of clean analysis for determining constituents at 

ultra-trace levels. 

3.3.2 Sample Containers 

 Sample container materials can introduce either positive or negative errors in 

measurement, particularly at low or ultra-trace levels, by contributing contaminants 

through leaching or surface desorption, or by depleting concentrations through adsorption. 

Additionally, the sample containers should be compatible with the reagents used for 

sample preservation. Thus, the collection and containment of the sample prior to analysis 

requires particular attention. Sample contamination introduced through field collection 

activities including sample containment and shipment can be assessed from the analysis 

of equipment rinsates and trip blanks. Guidelines on the selection of appropriate sample 

container materials for the collection of inorganic analytical samples are provided in Table 

3-1. 

3.3.3 Cleaning of Sample Containers 

 Sample containers should be scrupulously clean so as not to introduce 

contaminants that could interfere with quantification of the target analyte(s). This is of 

particular importance when determining trace or ultra-trace analyte concentration levels. 

The following cleaning sequence has been determined to be adequate to minimize 

contamination in the sample bottle, whether borosilicate glass, linear polyethylene, 

polypropylene, or PTFE: 

• Phosphate-free detergent 

• Tap water 

• 1:1 HNO3

• Tap water 

• 1:1 HCl 

• Tap water 

• Reagent water 

NOTE: Chromic acid should not be used to clean glassware, especially if chromium is 

to be included in the analytical scheme. Commercial, non-chromate products may be 

used in place of chromic acid, if adequate cleaning is documented by an analytical quality 

control program. Chromic acid should not be used with plastic bottles. 
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3.3.4 Sample Handling and Preservation 

 Recommended materials to use for sample collection are listed in Table 3-1. 

Sample holding times, recommended collection volumes or masses and recommended 

digestion volumes, and preservatives are listed in Table 3-2. The sample collection and 

digestion amounts depend on the combination of digestion or extraction and determinative 

procedures that will be employed for a given sample as well as the sensitivity and tolerable 

sampling errors that are required for a specific project (see References 20 through 22). 

Likewise, the use of alternative preservatives to those indicated in Table 3-2 may be 

necessary depending on the objectives of the project. In all cases, the sample quantity 

that is collected should be representative of the bulk material whenever feasible. 

3.3.5 Sample Preparation 

 For all non-speciated digestion methods, great reduction in analytical variability can 

be achieved through the use of appropriate sample preparation procedures. Generally, a 

reduction in subsampling variance can be accomplished by increasing the subsample 

aliquot size, reducing the sample particle size, and/or thoroughly mixing the resulting fines 

(see References 20 through 23 for additional information on sampling and sub-sampling). 

Under most circumstances, it is recommended that the sample be analyzed without drying. 

If it is necessary to report the analytical data on a dry-weight basis, then a separate aliquot 

may be analyzed for moisture content and the wet-weight data corrected accordingly. 

 If the sample cannot be well-mixed and homogenized in the form in which it was 

received by the laboratory, then air- or oven-drying at 30 °C or less, crushing, sieving, 

grinding, and mixing should be performed as needed or feasible to homogenize the 

sample until the subsampling variance is less than the data quality objectives of the 

analysis. While proper sample preparation generally produces great reduction in 

analytical variability, it should be noted that in certain unusual circumstances there could 

be loss of volatile metals (e.g., mercury, organometallics) or irreversible chemical changes 

( e.g., precipitation of insoluble species, change in valence state) caused by inappropriate 

sample preparation procedures. 

 Variability due to sample heterogeneity is assessed by analyzing individually 

prepared sample replicates such as field duplicates (FD), laboratory matrix duplicates 

(MD), and matrix spike (MS)/matrix spike duplicate (MSD). Variability inherent in the 

analytical determinative procedure can be assessed by matrix spiking of individually 

digested samples (i.e., post-digestion matrix spike) or by analyzing laboratory splits of the 

digestate. 

3.4 SPECIAL CONSIDERATIONS FOR DETERMINING INORGANIC ANALYTES AT ULTRATRACE CONCENTRATION LEVELS 

3.4.1 Clean Sampling Techniques 

 For the determination of ultra-trace analyte concentrations in environmental 

samples, it is essential that samples be collected and subsequently managed using 

techniques specifically designed to minimize sample contamination from field collection 

activities and to ensure target analyte stability. Such techniques represent a special 

category of sampling procedures designed specifically for ultra-trace analyses and are 

commonly referred to as clean or ultra-clean sampling procedures. Clean sampling 

methods are generally not intended for the determination of discharges from industrial 

facilities. Rather, they are primarily applicable for the determination of ambient element 

concentrations at levels of 0.1 ppb or less. At these concentrations, the opportunity for 
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sample contamination during sample collection or analysis in the laboratory is significant 

and should be managed accordingly. Figure 3-1 provides a demonstration of the impact of 

clean sampling and analysis techniques on data obtained for estuarine waters. Clean 

sampling typically involves the following key steps: 

• Special container pre-cleaning and pre-packaging requirements 

• Specific sampling equipment and container materials selection 

• Specific cleaning protocols for sampling equipment

• Equipment and container blank determinations prior to field use 

• "Clean hands/dirty hands" sample collection techniques based on a 2-person 

sampling crew 

- Dirty hands sampler manages sampling equipment only 

- Clean hands sampler manages the sample container 

• Special sample packaging prior to shipment 

• Use of a laboratory trained and properly equipped to perform clean analysis of 

the analytes of interest 

 Given the laboratory resources required to perform clean analysis techniques, it is 

paramount that samples be collected using ultra-clean techniques and conditions in the 

field. Otherwise, subsequent analytical efforts become futile. The information provided in 

this section is intended only as an introduction to the topic of clean sampling. Specific 

guidelines for clean sampling may be found in Reference 2 and other sources. 

3.4.2 Clean Analysis and the Analytical Blank 

 The significant role of the analytical blank in chemical analysis of trace metals 

cannot be overemphasized. Sensitive instrumentation such as ICP-MS, ICP-OES, and 

GFAA requires that sample preparation be at least as sophisticated as the instruments 

used for analysis. The analytical blank is normally a primary source of error in ultra-trace 

element analysis. Ultra-trace analysis is as dependent on control of the analytical blank as 

it is on the bias and precision of the instrument making the measurement. Inability to 

control contamination is frequently the limiting factor in trace (parts per million (ppm) to 

parts per billion (ppb)) and ultra-trace (ppb to parts per trillion (ppt)) analysis. Analytical 

blank contributions occur from the following four major sources (References 3 through 7): 

• The atmosphere in which the sample preparation and analysis are conducted 

• The purity and the quantities of the reagents used in sample preparation, 

including all reagents added directly to the sample

• The materials and equipment used in digestion or extraction vessels that come 

in contact with the sample during the sample preparation and analysis (i.e., the 

cleanliness and maintenance as well as their material properties). 

• The analyst’s technique and skill in preparing the samples and performing the 

analyses 

 The four primary areas that affect the analytical blank can be demonstrated using 

standard reference materials in analysis. Table 3-3 illustrates and isolates the main 

influencing parameters on the blank: environment, reagents, materials, and analyst skills. 

The skill of the analyst was kept constant as the same analyst changed the environment, 

reagents, and combinations of these parameters in the analysis (see Reference 6). The 

trace elements in glass (TEG) standard reference material from the National Institute of 

Standards and Technology (NIST) was used to keep sample homogeneity constant and to 

permit removal of the sampling error by using sample sizes in which appropriate 

homogeneity had previously been demonstrated. It is important to note that the 

relationship of the precision and measurement remained relatively constant. The 
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significance of the first two major sources of contamination, environment and reagents, is 

evaluated. The contamination in the laboratory air and in the acid used for the reagent 

blank altered the accuracy of the example above by over two orders of magnitude for both 

lead and silver. The larger influence of the two sources in this example is the laboratory 

environment in which the samples were prepared. 

3.4.2.1 Sample Preparation and Analysis Atmosphere 

 The atmosphere in which the sample is prepared is a major source of 

contamination for most target analytes when analyzing at ultra-trace levels. With 

the exception of some rare constituents, contamination from airborne sources 

represents the most significant of the four main contamination sources. For 

example, the mercury in a dental amalgam filling may cause blank 

contamination. To illustrate this point, Table 3-4 presents concentrations of lead 

found in samples of ambient air. 

 This contamination can also be seen in the comparison of 58,000 

particles per liter of air measured in a normal laboratory in Pittsburgh, PA, and 

inside a clean chamber in an adjacent laboratory five meters away. Figure 3-2 

demonstrates the dramatic difference between the two environments. Costeffective methods of creating clean chambers for sample preparation are 

documented along with this data in Reference 4. 

 Any laboratory air that comes into contact with the sample may deposit 

airborne contamination into the sample. The sample is especially vulnerable 

when it is being digested with acid. When samples are being digested with 

acid(s), contamination of the sample by particulates in the laboratory air can 

cause results that are biased high. 

 To prevent air from contaminating a sample for ultra-trace analysis, the 

sample should be processed in a clean environment. This is much easier to 

accomplish than it may appear at first. These precautions are becoming state-ofthe-art in many analytical and environmental laboratories. The prevention of 

airborne contamination is most frequently dealt with by employing a laminar flow 

clean bench or a clean laboratory facility. Instructions are referenced for the 

construction of both from component parts; both are relatively inexpensive and 

uncomplicated, once the concepts are understood (Reference 4). 

 There are many sources of airborne contamination. Several of the 

sources have been described and their particle size ranges are provided in 

Figure 3-3. These sources primarily provide particulates in discrete size ranges. 

Depending on whether the laboratory is located in an industrial, urban, or rural 

area, or near the sea, the distribution of these source particles will be different, 

as will their composition. The vertical dashed line in Figure 3 indicates the 

particle size cutoff, usually 0.5 μm, for the high efficiency particulate air (HEPA) 

filter used to prevent particulate contamination. Particles above this size cannot 

pass through a HEPA filter that is in good working order. These filters are in 

common use today (References 4 and 8). 

 The definition of clean air is derived from International Standard ISO 

14644-1, which defines cleanliness levels. Table 3-5 lists these conditions. 

"Laminar flow" is directed coherent air movement that does not contain any 

turbulence. 
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 A dramatic reduction in airborne contaminants can be achieved by using 

HEPA-filtered air in laminar-flow clean hoods or entire clean laboratories. Table 

3-6 demonstrates the dramatic differences in airborne contaminant 

concentrations in an ordinary laboratory, a clean laboratory, and a clean hood 

inside a clean laboratory. 

3.4.2.2 Reagent Purity for Ultra-trace Analysis 

 The purity of the reagents used for acid digestion, leaching, and 

extraction is extremely important to the overall level of the blank. Reagents have 

very different purities, depending on their processing grade and purpose. 

Frequently, the analyst should purchase special reagents, or purify lesser-grade 

reagents prior to use, in order to minimize the analytical blank. 

 

 In addition to the purity of the reagents, the quantity of reagent that is 

added to the sample may have a significant impact. When reagents are added, 

they bring with them elemental and molecular components that exist as 

contaminants. Increasing the reagent used in excess of the stoichiometric 

reaction, leads to greater potential for blank contamination. Reagents of high 

purity should either be purchased or produced in the laboratory. 

 In the preparation of high purity reagents, there is only one significant and 

practical choice for the method of purification, i.e., sub-boiling distillation 

(References 9 through 11). Different from normal distillation, sub-boiling 

distillation uses an infrared radiation source to heat the reagent to a temperature 

just below the boiling point. This use prevents the formation of bubbles that rise 

and burst at the surface of the liquid. Thus, the aerosolized solution particles are 

left in solution and prevented from physically transporting contaminants 

throughout the distillation apparatus. Sub-boiling distillation is a slower but very 

reliable method of purifying all of the common mineral acids and many organic 

reagents used in analytical methods. It relies exclusively on the vapor pressure 

of the reagent, and contaminant, and can therefore be specifically optimized for 

purification of the mineral acids if the object is to remove metal ions. Of all acids, 

nitric acid, for a variety of reasons, can be purified to excellent quality. Sources 

for sub-boiling apparatus equipment and methods for constructing one are 

provided in the references. Purchasing sub-boiling acids from commercial 

sources is also an option. Construction or purchase of sub-boiling reagent 

purification equipment may be cost effective for some laboratories depending on 

the quantity of reagents required for sample throughput. 

3.4.2.3 Materials for Sample Preparation, Storage, and Analysis 

 For ultra-trace analyses, only certain materials are preferred for use in the 

construction of sample vessels and instrument components that come into 

contact with the sample. Over the past two decades, materials identified as 

being non-contaminating have become the top choices for bottles, beakers, 

reaction vessels, storage containers, nebulizers, and instrument components for 

trace and ultra-trace analysis. The materials are the same as those currently 

being used in many digestion vessels, bomb liners, and microwave vessels. The 

materials are characterized by being thermally durable, chemically resistant or 

inert, non-contaminating, and possessing appropriate compression and tensile 

strength. Table 3-7 lists, in order of preference, several types of, noncontaminating materials that are chemically inert to most acid reactions. These 
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materials have been evaluated and tested extensively for their potential to 

contaminate (References 4, 6, 7, 12, and 13). 

 With the exception of polyethylene, the materials listed in Table 3-7 are 

those most commonly used for sample preparation vessels, both atmospheric 

pressure vessels and closed vessel liners that come into contact with the sample. 

These materials are the most stable to acid reactions (with the exception of 

quartz and glass if hydrofluoric acid is used). Fluoropolymers are the most 

common and were adapted from other chemical uses for application in pressure 

systems. The fluoropolymers have the highest range of use temperatures for 

most plastics, ranging from 270-300 °C. They are also chemically inert to the 

majority of mineral acids and combinations thereof. Sulfuric acid has a boiling 

point of approximately 330 °C and can damage all fluoropolymers by melting 

them. Quartz and glass can safely contain sulfuric acid at these high 

temperatures, but borosilicate glass is not appropriate for ultra-trace elemental 

analysis (References 7 and 13). Glass actually forms a gel layer that hydrates 

and leaches, transferring contaminants from the glass to the sample solution. 

While these quantities may be considered minute, they would be detected in 

blanks and samples undergoing ultra-trace analyses.

 Polyethylene is suitable for storage of diluted samples after digestion, but 

it does not have a thermal-use temperature appropriate for digestion. It is also 

not sufficiently inert to be useful as a digestion vessel or vessel liner, similar to 

polycarbonate and polypropylene. The low cost of polyethylene and its relative 

inertness to cool, weakly acidic solutions make it an excellent storage container 

for trace element solutions (Reference 4). 

3.4.2.4 Analytical Technique and Synergistic Equipment 

 The fourth significant source of analytical blank contamination is the skill 

of the analyst and the appropriateness of the technique being performed. 

Analytical blank control has been explained as the combination of atmosphere, 

reagent, material, and protocol being performed. Also, the skill and awareness of 

the analyst as well as the way in which the combinations of the aforementioned 

clean chemistry techniques are applied will have a significant effect on the final 

contamination error and analytical blank control. Sample preparation 

instrumentation may also assist in these protocols. For example, microwave 

sample preparation assists each of these parameters in synergistic ways, thus 

lowering the analytical blank, improving blank precision, and enhancing overall 

quality control and transferability of methods. Some instrumentation and 

fundamental processes involved in specific sample preparation procedures 

assists the analyst by incorporating useful clean chemistry concepts into 

instrumentation and method structure. Such instrumentation is pertinent since 

microwave methods now exist that provide sample preparation for leaching or 

total analysis of many target analytes simultaneously. As an example, the skill of 

the analyst with regard to clean chemistry is assisted by the method structure 

and microwave equipment as indicated below: 

• If a closed or controlled atmospheric microwave vessel is prepared in a clean 

hood and sealed before leaving the clean environment, the sample will not be 

affected by atmospheric contamination during the reaction, since it has not 

been removed from a clean environment. 
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• The vessel materials described previously might not normally be used by 

many laboratories, and therefore the advantages of the fluoropolymers would 

not be realized if they were not required in most microwave reaction vessels 

as they commonly are. 

• The time that the sample spends in digestion, leaching, or extraction may be 

reduced from hours to minutes, thus reducing the potential leaching of 

contaminants from the container walls. 

• Because most microwave systems are sealed systems, evaporation of the 

reagent before it reacts productively is prevented and smaller quantities of 

reagents are used, thus preventing excess and unnecessary accumulation of 

contaminants in the blank. 

 By reducing the exposure variables, the blank variability is consequently 

reduced in size and is more consistent. An example of these components 

working together has been provided in the literature, where analysis under 

different conditions has verified these conclusions (References 4, 14 and 15). 

The example illustrates the isolation of the blank optimization areas: 

environment, reagents, materials, and analyst skills. The skill of the analyst is 

kept more constant as the instrument dictates cleaner, chemically-appropriate 

procedures. 

3.5 REAGENT PURITY 

 The purity of the reagents used for sample preservation, acid digestion, leaching, 

extraction and analysis is extremely important for preventing or minimizing sample 

contamination. Reagents have very different purities, depending on their processing grade and 

purpose. Reagent grade, ACS grade or better are recommended for use with most SW-846 

methods. Sample contamination introduced through sample preservation, handling, preparation 

and analysis is assessed from the analysis of method blanks. 

3.6 SAMPLE DIGESTION METHODS 

Many of the methods listed below employ HCl in the digestion process. Chlorine is an 

interferant in ICP-MS analysis and its use in sample digestion is discouraged except when 

absolutely necessary or when the instrument manufacturer has indicated that the use of HCl will 

not adversely affect the equipment and accurate quantitation of the desired target analytes. 

However, please note that recoveries of certain metals may be biased low when using nitric acid 

only. Interference from chlorine may be minimized by use of collision or reaction cell 

instrumentation. 

 The methods in SW-846 for sample digestion or dissolution include: 

Method 3005A: Acid Digestion of Waters for Total Recoverable or Dissolved Metals for 

Analysis by FLAA or ICP Spectroscopy 

 This method may be used for the preparation of ground water and surface water samples 

for total recoverable and dissolved metal determinations by FLAA, ICP-OES, or ICP-MS. The 

unfiltered or filtered sample is heated with dilute HCl and HNO3 prior to metal determination. 
SW-846 Update V THREE - 12 Revision 5 

October 2012 

Method 3010A: Acid Digestion of Aqueous Samples and Extracts for Total Metals for Analysis 

by FLAA or ICP Spectroscopy 

 This method may be used for the preparation of waste samples for total recoverable metal 

determinations by FLAA, ICP-OES, or ICP-MS. The samples are vigorously digested with nitric 

acid followed by dilution with hydrochloric acid. The method is applicable to aqueous samples, 

leachates, and mobility-procedure extracts. 

Method 3015A: Microwave Assisted Acid Digestion of Aqueous Samples and Extracts

 This method may be used for the preparation of aqueous samples, mobility-procedure 

extracts, and wastes that contain suspended solids for total recoverable metal determinations 

by FLAA, GFAA, ICP-OES, or ICP-MS. Nitric acid and hydrochloric acid are added to the 

sample in a PTFE digestion vessel and heated in a microwave unit prior to metals 

determination. 

Method 3020A: Acid Digestion of Aqueous Samples and Extracts for Total Metals for Analysis 

by GFAA Spectroscopy 

 This method may be used for the preparation of waste samples for total recoverable 

metals determinations by GFAA or ICP-MS. The samples are vigorously digested with nitric 

acid followed by dilution with nitric acid. The method is applicable to aqueous samples, 

leachates, and mobility-procedure extracts. 

Method 3031: Acid Digestion of Oils for Metals Analysis by Atomic Absorption or ICP 

Spectrometry 

 This method may be used for the preparation of waste oils, oil sludges, tars, waxes, 

paints, paint sludges and other viscous petroleum products for analysis by FLAA, GFAA, and 

ICP-OES. The samples are vigorously digested with nitric acid, sulfuric acid, hydrochloric acid, 

and potassium permanganate prior to analysis. 

 

Method 3040A: Dissolution Procedure for Oils, Greases, or Waxes

 This method may be used for the preparation of oily waste samples for determination of 

soluble metals by FLAA and ICP-OES. The samples are dissolved and diluted in organic 

solvent prior to analysis. The method is applicable to the organic extract in the oily waste EP 

procedure and other samples high in oil, grease, or wax content. 

Method 3050B: Acid Digestion of Sediments, Sludges, and Soils 

 This method may be used for the preparation of waste samples for total recoverable 

metals determinations by FLAA and ICP-OES, or GFAA and ICP-MS depending on the options 

chosen. The samples are vigorously digested in nitric acid and hydrogen peroxide followed by 

dilution with either nitric or hydrochloric acid. The method is applicable to soils, sludges, and 

solid waste samples. 

Method 3051A: Microwave Assisted Acid Digestion of Sediments, Sludges, Soils, and Oils 

 This method may be used for the preparation of sludges, sediments, soils and oils for total 

recoverable metal determinations by FLAA, GFAA, ICP-OES or ICP-MS. Nitric acid and 

hydrochloric acid are added to the representative sample in a fluorocarbon digestion vessel and 

heated in a microwave unit prior to metals determination. 
SW-846 Update V THREE - 13 Revision 5 

October 2012 

Method 3052: Microwave Assisted Acid Digestion of Siliceous and Organically Based Matrices 

 This method may be used for the preparation of siliceous and organically based matrices 

including ash, biological tissue, oil, oil contaminated soil, sediment, sludge, and soil for total 

metals analysis by FLAA, CVAA, GFAA, ICP-OES, and ICP-MS. Nitric acid and hydrofluoric 

acid are added to a representative sample in a fluorocarbon digestion vessel and heated in a 

microwave unit prior to analysis. 

Method 3060A: Alkaline Digestion for Hexavalent Chromium 

 This method may be used for the preparation of soils, sludges, sediments and similar 

waste materials for hexavalent chromium determination. The samples are digested and heated 

to dissolve the Cr(VI) and stabilize it against reduction to Cr(III). 

Method 3200: Mercury Species Fractionation and Quantification by Microwave Assisted 

Extraction, Selective Solvent Extraction and/or Solid Phase Extraction 

This method uses sequential extraction and separation procedures to differentiate 

mercury species that are present in soils and sediments into four distinct fractions: extractable 

organic mercury, extractable inorganic mercury, semi-mobile mercury and non-mobile mercury. 

Extraction is accomplished with the aid of either microwave irradiation or ultrasound. 

Quantification of mercury in the different fractions may be performed using any appropriate 

determinative method, (e.g., Method 7473, 1631, or Methods 7470 and 7471). The test method 

also contains provisions for separating and quantifying individual extractable mercury species 

using HPLC. 

3.7 METHODS FOR DETERMINATION OF INORGANIC ANALYTES

 This section of the manual contains analytical techniques for trace inorganic analyte 

determinations. Instrumental techniques include: 

- Inductively coupled argon plasma optical emission spectrometry (ICP-OES), 

- Inductively coupled plasma mass spectrometry (ICP-MS), 

- Direct-aspiration or flame atomic absorption spectrophotometry (FLAA), 

- Graphite furnace atomic absorption spectrophotometry (GFAA), 

- Hydride-generation atomic absorption spectrometry (HGAA), 

- Cold-vapor atomic absorption spectrometry (CVAA), 

- Cold-vapor atomic fluorescence spectrometry (CVAF), 

- Anodic stripping voltammetry (ASV), 

- X-ray fluorescence (XRF), 

- Ion chromatography (IC) 

- Capillary electrophoresis (CE) 

- Speciated isotope dilution mass spectrometry (SIDMS) and 

- Several procedures for hexavalent chromium analysis. 

Each of these (except the individual hexavalent chromium analyses) is discussed briefly below. 

Some advantages, disadvantages, and cautions for the analysis of wastes are provided. 

 ICP-OES allows simultaneous or rapid sequential determination of many elements in a 

short time. Aerosol samples are introduced into an extremely hot plasma source which 

vaporizes, atomizes, and ionizes the sample components. Upon exiting the plasma, the 
SW-846 Update V THREE - 14 Revision 5 

October 2012 

electronically excited analytes emit characteristic photons that are detected via emission 

spectrometry. A primary disadvantage of ICP-OES is the occurrence of background radiation 

from other elements and the plasma gases. Although all ICP-OES instruments utilize highresolution optics and background correction to minimize these interferences, analysis of trace 

levels of inorganic analytes in the presence of a large excess of a single analyte is difficult. 

Examples would be trace levels of inorganic analytes in an alloy or trace metals in a limed (high 

calcium) waste. ICP-OES and FLAA have comparable detection limits (within a factor of 4) 

except that ICP-OES exhibits greater sensitivity for refractories (Al, Ba, etc.). Further, the wide 

dynamic ranges and multi-element capabilities make ICP-OES instruments more productive. 

GFAA, in general, will exhibit lower detection limits than either ICP-OES or FLAA. 

 ICP-MS allows sensitive, simultaneous determination of many elements in a short time 

frame using MS detection in place of OES. In general ICP-MS exhibits greater sensitivity than 

GFAA, FLAA or ICP-OES for most elements. The main disadvantage of ICP-MS is isobaric 

elemental interferences. These are caused by different elements or molecular species forming 

ions with the same nominal mass-to-charge ratio. Mathematical correction for interfering ions 

can minimize these interferences, but the most effective means of removal of molecular isobaric 

interferences is the collision or reaction cell. 

 

 FLAA direct-aspiration determinations, as opposed to ICP-OES or ICP-MS, are normally 

completed as single-element analyses and are relatively free of interelement spectral 

interferences. Either a nitrous-oxide/acetylene or air/acetylene flame is used as an energy 

source for dissociating the aspirated sample into the free atomic state, making analyte atoms 

available for absorption of light and spectrophotometric detection. In the analysis of some 

elements, the temperature or type of flame used is critical. If the proper flame and analytical 

conditions are not used, chemical and ionization interferences can occur. 

 GFAA replaces the flame with an electrically-heated graphite furnace. The furnace allows 

for gradual heating of the sample aliquot in several stages. Thus, the processes of dissolution, 

drying, decomposition of organic and inorganic molecules and salts, and formation of atoms, 

which should occur in a flame or plasma in a few milliseconds may be allowed to occur over a 

much longer time period and at controlled temperatures in the furnace. This allows an 

experienced analyst to remove unwanted matrix components by using temperature 

programming and/or matrix modifiers. The major advantage of this technique is that it affords 

extremely low detection limits. It is the easiest to perform on relatively clean samples. Because 

this technique is so sensitive, interferences can be a real problem; finding the optimum 

combination of digestion, heating times and temperatures, and matrix modifiers can be a 

challenge for complex matrices. 

 

 HGAA utilizes a chemical reduction to reduce and separate arsenic, selenium, or antimony 

selectively from a sample digestate. The technique therefore has the advantage of being able 

to isolate these elements from complex samples which may cause interferences for other 

analytical procedures. Significant interferences have been reported when any of the following is 

present: (1) easily reduced metals (Cu, Ag, and Hg); (2) high concentrations of transition metals 

(>200 mg/L); (3) oxidizing agents (oxides of nitrogen) remaining following sample digestion. 

 

 CVAA uses chemical reduction to reduce mercury to its volatile elemental form. The 

procedure is sensitive, though not as sensitive as CVAF, but is subject to interferences from 

some volatile organics, chlorine, and sulfur compounds. CVAA may be more appropriate than 

CVAF for samples with higher mercury concentrations. 

 CVAF uses chemical reduction to reduce mercury to its volatile elemental form. The 

procedure is extremely sensitive, approximately one to two orders of magnitude more sensitive 

than CVAA. CVAF may be more appropriate than CVAA for samples with low mercury 
SW-846 Update V THREE - 15 Revision 5 

October 2012 

concentrations. Because of the extreme sensitivity of CVAF, contamination during sampling 

and analysis is a major concern. 

 ASV is an electrochemical method that can be used for determining free dissolved metals 

such as arsenic and mercury. The analyte of interest is reduced at the electrode surface during 

a deposition step and oxidized from the electrode during a stripping step; the current measured 

during the stripping step is proportional to the analyte concentration. ASV detects dissolved 

divalent mercury species and cannot directly distinguish between organic and inorganic mercury 

compounds. The sensitivity of this method for mercury is similar to CVAA. ASV detects 

dissolved inorganic arsenic species and can distinguish between As(III) and As(V) by adjusting 

the potential applied during the deposition step. The sensitivity of this method for arsenic is 

about an order of magnitude more sensitive than ICP-MS, GFAA, or HGAA. This method is 

subject to interferences from suspended solids, organics, and other metals. Samples can be 

modified (e.g., digested, addition of chelating agent, etc.) to determine the concentration of 

various species of the analyte of interest (e.g., total fraction, methylmercury, etc.) 

 XRF uses sealed radioisotope sources or other suitable X-ray source to irradiate samples 

with X-rays. When a sample is irradiated with X-rays, the source X-rays may undergo either 

scattering or absorption by sample atoms. This later process is known as the photoelectric 

effect. When an atom absorbs the source X-rays, the incident radiation dislodges electrons 

from the innermost shells of the atom, creating vacancies. The electron vacancies are filled by 

electrons cascading in from outer electron shells. Electrons in outer shells have higher energy 

states than inner shell electrons, and the outer shell electrons give off energy as they cascade 

down into the inner shell vacancies. This rearrangement of electrons results in emission of Xrays characteristic of the given atom. The emission of X-rays, in this manner, is termed X-ray 

fluorescence. 

 IC generally refers to the separation of ions through ion exchange chromatography. In this 

technique, an aqueous sample is injected into a mobile solution that is carried into a 

chromatography column. As the sample travels through the column, the sample analytes are 

temporarily retained on the column, the stationary phase, via electrostatic forces. The 

separated analytes are identified as they are released from the column based on their retention 

time. Detection and quantification in IC are most commonly performed using conductivity 

detection. IC is typically used for the determination of anionic analytes in waste samples. 

 CE refers to the electrophoretic separation of ions dissolved or suspended in an 

electrolyte. Samples are introduced into a capillary tube containing an electrolytic buffer. Under 

the application of an electric field the cations in the sample migrate toward the negatively 

charged electrode (cathode) and the anions migrate toward the positively charged electrode 

(anode). This technique may be coupled with a variety of determinative techniques for 

quantitative analysis. Inorganic anions can be determined in environmental samples using CE 

and indirect UV detection, in which analytes are detected and quantified based on proportional 

decreases in the absorbance of the buffer solution. CE is a complementary technique to IC and 

typically offers shorter analysis times than IC. 

 SIDMS is a quantitative method for determining elemental species based on the 

measurement of isotope ratio(s) in each species of a nuclide using mass spectrometry after 

speciated isotope dilution. Samples are mixed with one or more isotopic spikes which have 

different isotopic abundances and are artificially converted to chemical forms corresponding to 

the species to be analyzed. The spiked samples are then subjected to the separation of the 

species and the measurement of the altered isotope ratios in each species. Both species 

concentrations and species conversions can be mathematically derived. 
SW-846 Update V THREE - 16 Revision 5 

October 2012 

 The following methods are included in this section: 

Method 6010D: Inductively Coupled Plasma-Optical Emission Spectrometry 

Method 6020B: Inductively Coupled Plasma-Mass Spectrometry 

Method 6200: Field Portable X-Ray Fluorescence Spectrometry for the Determination 

of Elemental Concentrations in Soil and Sediment 

Method 6500: Dissolved Inorganic Anions in Aqueous Matrices by Capillary Ion 

Electrophoresis 

Method 6800: Elemental and Speciated Isotope Dilution Mass Spectrometry 

Method 7000B: Flame Atomic Absorption Spectrophotometry 

Method 7010: Graphite Furnace Atomic Absorption Spectrophotometry 

 Method 7061A: Arsenic (Atomic Absorption, Gaseous Hydride) 

Method 7062: Antimony and Arsenic (Atomic Absorption, Borohydride Reduction) 

Method 7063: Arsenic in Aqueous Samples and Extracts by Anodic Stripping 

Voltammetry (ASV) 

Method 7195: Chromium, Hexavalent (Coprecipitation) 

Method 7196A: Chromium, Hexavalent (Colorimetric) 

Method 7197: Chromium, Hexavalent (Chelation/Extraction) 

Method 7198: Chromium, Hexavalent (Differential Pulse Polarography) 

Method 7199: Determination of Hexavalent Chromium in Drinking Water, 

Groundwater and Industrial Wastewater Effluents by Ion 

Chromatography 

Method 7470A: Mercury in Liquid Waste (Manual Cold-Vapor Technique) 

Method 7471B: Mercury in Solid or Semisolid Waste (Manual Cold-Vapor Technique) 

Method 7472: Mercury in Aqueous Samples and Extracts by Anodic Stripping 

Voltammetry (ASV) 

Method 7473: Mercury in Solids and Solutions by Thermal Decomposition, 

Amalgamation, and Atomic Absorption Spectrophotometry 

Method 7474: Mercury in Sediment and Tissue Samples by Atomic Fluorescence 

Spectrometry 

Method 7580: White Phosphorus (P4) by Solvent Extraction and Gas 

Chromatography 

Method 7741A: Selenium (Atomic Absorption, Gaseous Hydride) 

Method 7742: Selenium (Atomic Absorption, Borohydride Reduction) 

3.8 REFERENCES FOR PREVIOUS SECTIONS AND THE TABLES AND FIGURES 

1. Skoog, D. A., "Principles of Instrumental Analysis," 3rd ed, Saunders College Publishing, 

Philadelphia, PA, 1985. 

2. EPA, U.S., "Sampling Ambient Water for Trace Metals at EPA Water Quality Criteria 

Levels," Method 1669, U.S. Environmental Protection Agency, Office of Water, 

Washington, D.C., 1996. 

3. Adeloju, S. B. and Bond, A. M., "Influence of Laboratory Environment on the Precision and 

Accuracy of Trace Element Analysis," Anal. Chem., 1985, 57, 1728-1733. 
SW-846 Update V THREE - 17 Revision 5 

October 2012 

4. Kingston, S. H. M., et al., "Microwave Enhanced Chemistry: Fundamentals, Sample 

Preparation, and Applications," American Chemical Society, Washington, DC, 1997, p. 

257-279. 

5. Moody, J. R., "NBS Clean Laboratories for Trace Element Analysis," Anal. Chem., 1982, 

54, 1358A-1376A. 

6. Murphy, T., "National Bureau of Standards Special Publication 422 Accuracy in Trace 

Analysis: Sampling, Sample Handling, and Analysis," National Bureau of Standards, 

Gaithersburg, MD, 1976, p. 509-539. 

7. Tolg, G. and Tschopel, P., "Determination of Trace Elements," VCH, New York, NY, 1994, 

p. 1-38. 

8. Zief, M. and Mitchell, J. W., "Chemical Analysis," Vol. 47, John Wiley & Sons, New York, 

NY, 1976. 

9. Kuehner, E. C., et al., "Production and Analysis of Special High-Purity Acids Purified by 

Sub-Boiling Distillation," Anal. Chem., 1972, 44, 2050-2056. 

10. Moody, J. R., "Purified Reagents for Trace Metal Analysis," Talanta, 1982, 29, 1003-1010. 

11. Kuehner, E. C. and Freeman, D. H., "Purification of Inorganic and Organic Materials," 

Marcel Dekker, New York, NY, 1969, p. 297-306. 

12. Moody, J. R., "The Sampling, Handling and Storage of Materials for Trace Analysis," 

Philos. Trans. R. Soc. London, 1982, 305, 669-680. 

13. Moody, J. R. and Lindstrom, R. M., "Selection and Cleaning of Plastic Containers for 

Storage of Trace Element Samples," Anal. Chem., 1977, 49, 2264-2267. 

14. Prevatt, F. J., "Clean Chemistry for Trace Analysis," Environmental Testing and Analysis, 

1995, 4, 24-27. 

15. Skelly, E. M. and DiStefano, F. T., "Clean Room and Microwave Digestion Techniques: 

Improvement in Detection Limits for Aluminum Determination by GF-AAS," Appl. 

Spectrosc., 1988, 42, 1302-1306. 

16. Rabinowitz, M. B. and Wetherill, G. W., "Identifying Sources of Lead Contamination by 

Stable Isotope Techniques," Environ. Sci. Technol., 1972, 6, 705-709. 

17. Maienthal, E. J., "U.S. National Bureau of Standards Technical Note 545," National 

Bureau of Standards, Gaithersburg, MD, 1970, p. 53-54. 
SW-846 Update V THREE - 18 Revision 5 

October 2012 

18. Boothe, P. N. and Nicolau, B.A. "The Coastal Bend Bays Project," 26th Annual 

Conference on Analysis of Pollutants in the Environment, Chicago, IL 2003. 

19. Miller, G. T., "Living in the Environment, Wadsworth Inc., Belmont, CA, 1994. 

20. Gy, P., "Sampling for Analytical Purposes" Wiley, New York, NY, 1998. 

21. Pitard F.F. “Pierre Gy’s Sampling Theory and Sampling Practice,” Second Edition, CRC 

Press, Inc., Boca Raton, FL, 1993. 

22. EPA, U.S., “Correct Sampling Using the Theories of Pierre Gy,” Office of Research and 

Development, Las Vegas, NV, 1999. 

23. EPA, U.S., “Guidance for Obtaining Representative Laboratory Analytical Subsamples 

from Particulate Laboratory Samples.” Office of Research and Development, 2003. 
SW-846 Update V THREE - 19 Revision 5 

October 2012 

TABLE 3-1 

MATERIALS FOR USE IN SAMPLE COLLECTION FOR 

INORGANIC ANALYTE DETERMINATIONS 

Analyte Recommended Container Material 

Metals PTFE, plastic, glass 

Chloride PTFE, plastic, glass 

Cyanide PTFE, plastic 

Fluoride PTFE, plastic 

Nitrate PTFE, plastic, glass 

pH PTFE, plastic, glass 

Specific Conductance PTFE, plastic, glass 

Sulfate PTFE, plastic, glass 

Sulfide PTFE, plastic, glass 

a

These recommendations are intended as guidance only and not inclusive of all possible analytes and 

materials. The selection of sample container should be made based on the nature of the sample, the 

intended end use of the data and the project data quality objectives. 

 

 
SW-846 Update V THREE - 20 Revision 5 

October 2012 

TABLE 3-2 

RECOMMENDED SAMPLE HOLDING TIMES, PRESERVATION, COLLECTION QUANTITIES, 

AND DIGESTION VOLUMES FOR SELECTED INORGANIC ANALYTE DETERMINATIONS IN 

AQUEOUS AND SOLID SAMPLES a,b

Analyte Matrix Fraction 

Minimum 

Collection 

Volume/Mass 

Preservation

1

Digestion

Volume 

Holding 

Time 2

Metals (except 

Hg and Cr6+) 

Aqueous Total/total 

recoverable 

600 mL HNO3 to pH<2 100 mL 6 months 

 Dissolved 600 mL Filter on site; 

HNO3 to pH<2 

100 mL 6 months 

 Suspended 600 mL Filter on site; 100 mL 6 months 

 Solid Total 200 g None 2 g 6 months 

Hexavalent 

chromium 

Aqueous 400 mL ≤6 °C 100 mL 24 hours 

 Solid 100 g ≤6 °C 30 days to 

extraction 

 ≤6 °C 2.5 g 7 days from 

extraction to 

analysis 

Mercury Aqueous Total 400 mL HNO3 to pH<2 100 mL 28 days 

 Dissolved 400 mL Filter; 

HNO3 to pH<2 

100 mL 28 days 

 Solid Total 200 g ≤6 °C 0.2 g 28 days 

 Solid Species 200 g ≤6 °C 0.2 g 5 days 

Chloride Aqueous 50 mL ≤6 °C  28 days 

Cyanide Aqueous 500 mL ≤6 °C; 

NaOH to 

pH>12 

 14 days 

 Solid 100 g ≤6 °C  14 days 

Fluoride Aqueous 300 mL ≤6 °C  28 days 

Nitrate Aqueous 1000 mL ≤6 °C  28 days 

 

Hexane 

Extractable 

Material 

(HEM; Oil & 

Grease) 

Aqueous 

Solid 

 1000 mL 

100 g 

≤6 °C 

HCl or H2SO4 

to pH <2 

≤6 °C 

 28 days 

28 days 

 HCl or H2SO4 

to pH <2 

 when 

practical 
SW-846 Update V THREE - 21 Revision 5 

October 2012 

TABLE 3-2 

RECOMMENDED SAMPLE HOLDING TIMES, PRESERVATION, COLLECTION QUANTITIES, 

AND DIGESTION VOLUMES FOR SELECTED INORGANIC ANALYTE DETERMINATIONS IN 

AQUEOUS AND SOLID SAMPLES a,b

Analyte Matrix Fraction 

Minimum 

Collection 

Volume/Mass 

Preservation

1

Digestion

Volume 

Holding 

Time 2

 

pH Aqueous 25 mL NA  Analyze 

immediately 

 Solid 20 g NA  Analyze 

immediately 

Specific 

Conductance 

Aqueous 100 mL NA  Analyze 

immediately 

Sulfate Aqueous 50 mL ≤6 °C  28 days 

Sulfide Aqueous 

Solid 

100 mL 

100 g 

4 drops 2N 

zinc 

acetate/100 

mL sample; 

NaOH to 

pH>9; 

Minimize 

aeration; 

Store 

headspace 

free at 

≤6 °C 

Fill sample 

surface with 

2N zinc 

acetate until 

moistened; 

Store 

headspace 

free at ≤6 °C 





7 days 

7 days 

Organic 

Carbon, Total 

(TOC) 

Aqueous 

Solid 

 200 mL 

100 g 

≤6 °C 

store in dark 

HCl or H2SO4 

to pH <2; 

≤6 °C 





28 days 

28 days 

a These recommendations are intended as guidance only. The selection of sample and digestion volumes and 

preservation and holding times should be made based on the nature of the sample, the intended end use of the data 

and the data quality objectives. 

b

 Additional sample quantities may need to be collected in order to allow for the preparation and analysis of QC 

samples, such as matrix spikes and duplicates. 

1 The exact sample extract, and standard storage temperature should be based on project-specific requirements 

and/or manufacturer’s recommendations for standards. Alternative temperatures may be appropriate based on 

demonstrated analyte stability within a matrix, provided the data quality objectives for a specific project are still 

attainable. 
SW-846 Update V THREE - 22 Revision 5 

October 2012 

2

 A longer holding time may be appropriate if it can be demonstrated that the reported analyte concentrations are not 

adversely affected by preservation, storage and analyses performed outside the recommended holding times.

TABLE 3-3 

EXAMPLES OF THE ANALYTICAL BLANK INFLUENCE ON 

ULTRA-TRACE ANALYSIS OF ELEMENTS IN GLASS 

Conditions Pb (ng) Ag (ng) 

Initial analysis of TEG* standard 330 ± 250 970 ± 500 

Analysis using sub-boiled distilled acids 260 ± 200 - 

Analysis in a Class 100 hood 20 ± 8 207 ± 200 

Analysis using sub-boiled acids in a Class 100 hood 2 ± 1 3 ± 2 

* TEG = Trace element in glass 

Data are taken from Reference 6. 

TABLE 3-4 

EXAMPLES OF LEAD CONCENTRATIONS IN AIR 

Site Lead Concentration (μg/m3

) Source 

Downtown St. Louis, MO 18.84 Reference 16 

Rural park, Southeastern MO 0.77 Reference 17 

NIST Laboratory, MD 0.4 Reference 6 
SW-846 Update V THREE - 23 Revision 5 

October 2012 

TABLE 3-5 

CLEANLINESS LEVELS IN INTERNATIONAL STANDARD ISO 14644-1 

ISO 

classification 

number 

Maximum concentration limits (particles/m-3

 of air) for particles equal to and 

larger than the considered sizes shown below 

0.1 μm 0.2 μm 0.3 μm 0.5 μm 1 μm 5 μm 

ISO Class 1 10 2 

ISO Class 2 100 24 10 4 

ISO Class 3 1,000 237 102 35 8 

ISO Class 4 10,000 2,370 1,020 352 83 

ISO Class 5 100,000 23,700 10,200 3,520 832 29 

ISO Class 6 1,000,000 237,000 102,000 35,200 8,320 293 

ISO Class 7 352,000 83,200 2,930 

ISO Class 8 3,520,000 832,000 29,300 

ISO Class 9 35,200,000 8,320,000 293,000 

NOTE: Uncertainties related to the measurement process require that concentration data with no more 

than three significant figures be used in determining the classification level 

© ISO. This material is reproduced from ISO 14644-1:1999 with permission of the American 

National Standards Institute (ANSI) on behalf of the International Organization for 

Standardization (ISO). No part of this material may be copied or reproduced in any form, 

electronic retrieval system or otherwise or made available on the Internet, a public network, by 

satellite or otherwise without the prior written consent of ANSI. Copies of this standard may be 

purchased from ANSI, 25 West 43rd Street, New York, NY 10036, (212) 642-4900, 

http://webstore.ansi.org. 

 
SW-846 Update V THREE - 24 Revision 5 

October 2012 

TABLE 3-6 

PARTICULATE CONCENTRATIONS IN LABORATORY AIR 

Concentration (μg/m3

) 

Location Iron Copper Lead Cadmium 

Ordinary 

laboratory 0.2 0.02 0.4 0.002 

Clean room 0.001 0.002 0.0002 ND 

Clean hood 0.0009 0.007 0.0003 0.0002 

ND = Not Detected 

Data are taken from Reference 17. 

TABLE 3-7 

NON-CONTAMINATING MATERIALS AND FOR USE AS DIGESTION VESSELS 

AND SAMPLE CONTAINERS IN ULTRA-TRACE ANALYSES 

Listed from highest to lowest preference for use in sample containment 

Fluoropolymers: PFA*, TFM, TFE*, FEP*, Tefzel* 

Quartz - Synthetic 

Polyethylene (suitable for storage only, not for acid digestion) 

Quartz - Natural 

Borosilicate Glass 

* Various forms of PTFE 

Data are taken from Reference 8. 
SW-846 Update V THREE - 25 Revision 5 

October 2012 

FIGURE 3-1 

COMPARISON OF CLEAN VERSUS CONVENTIONAL SAMPLING AND ANALYSIS 

TECHNIQUES USED IN THE ANALYSIS OF SOUTH TEXAS ESTUARY WATERS 

Taken from Reference 18. 

0

10

20

30

40

Cd Cu Hg Pb Zn

Element

Concentration (ppb)

Clean Conventional

11 fold

10 fold

36 fold

280 fold

26 fold
SW-846 Update V THREE - 26 Revision 5 

October 2012 

FIGURE 3-2 

COMPARISON OF PARTICLE COUNT ANALYSIS OF A CLEAN ROOM AND 

A STANDARD LABORATORY AT DUQUESNE UNIVERSITY IN PITTSBURGH, PA 

Taken from Reference 4. 
SW-846 Update V THREE - 27 Revision 5 

October 2012 

FIGURE 3-3 

PARTICLE SIZE COMPARISON CHART FOR COMMON PARTICULATES 

Taken from Reference 4, 19. 
SW-846 Update V THREE - 28 Revision 5 

October 2012 

APPENDIX A 

SUMMARY OF UPDATES/CHANGES IN CHAPTER THREE 

1. The entire document was formatted in Microsoft Word 2007 .docx format from the 

original .wpd and .pdf files. 

2. The Revision number was changed to Revision 5, updated for release October 2012. 

3. Minor editorial and grammatical changes were made throughout the Chapter. 

4. Method 3200 was added to Section 3.6. 

5. Method numbers were revised to reflect the assigned number for Update V. 

6. Definition for instrument detection limit (IDL) was revised to be consistent with methods 

6010D and 6020B. 

7. The term “accuracy” was replaced by “bias” where appropriate. 

8. Definition for linear range was revised to be consistent with methods 6010D and 6020B. 

9. All references to atomic emission spectrometry were changed to optical emission 

spectrometry throughout the chapter. 

10. Replaced the definition of interference check sample (ICS) with the spectral interference 

check (SIC) solution to be consistent with methods 6010D and 6020B. 

11. Added a note to clarify the methods that can be used for total acid soluble/recoverable 

metals. 

12. References 20-22 were added as guidance for minimizing sampling bias. 

13. The term “decomposition” was replaced by “digestion” where appropriate. 

14. Descriptions of cold vapor atomic fluorescence and anodic stripping voltammetry were 

added to Section 3.7. 

15. Collision/reaction cell technology was added to Sections 3.6 and 3.7 as an effective 

method for removing isobaric interferences when analyzing by ICP-MS. 

16. The terms "analytical" and "analysis" were changed to "instrument" or "determinative", 

where appropriate. 

17. The term “signal” was changed to “instrument response”. 

18. The method for assessing sensitivity for ICP-OES and ICP-MS in Section 3.1 was 

modified. 

19. The term “optimum concentration range” was removed from Section 3.1. 

20. Antimony was added to the HGAA method described in Section 3.7. 

21. The definition for “laboratory control sample” was revised to recommend the use of a 

spiking solution from the same source as the calibration standards. 

22. A minimum collection mass of 100 g was added to Table 3-2 for solid samples collected 

for sulfide analysis.