«Section � Page 3.0 � INTRODUCTION 1 � 3.1 � DEFINITIONS 1 � 3.2 � SAFETY 4 � 3.3 � SAMPLING CONSIDERATIONS 4 � 3.4 � SPECIAL ...»
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 6�
ULTRATRACE CONCENTRATION LEVELS� 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 �
31 MATERIALS FOR USE IN SAMPLE COLLECTION FOR INORGANIC ANALYTE 18�
32 RECOMMENDED SAMPLE HOLDING TIMES, PRESERVATION, COLLECTION 19�
QUANTITIES, AND DIGESTION VOLUMES FOR SELECTED INORGANIC ANALYTE�
DETERMINATIONS IN AQUEOUS AND SOLID SAMPLES�
33 EXAMPLES OF THE ANALYTICAL BLANK INFLUENCE ON ULTRATRACE 21�
ANALYSIS OF ELEMENTS IN GLASS�
34 EXAMPLES OF LEAD CONCENTRATIONS IN AIR 21� 35 CLEANLINESS LEVELS IN INTERNATIONAL STANDARD ISO 146441 22 �
36 PARTICULATE CONCENTRATIONS IN LABORATORY AIR 23�
37 NONCONTAMINATING MATERIALS AND FOR USE AS DIGESTION VESSELS AND 23�
SAMPLE CONTAINERS IN ULTRATRACE ANALYSIS�
31 COMPARISON OF CLEAN VERSUS CONVENTIONAL SAMPLING AND ANALYSIS 24�
TECHNIQUES USED IN THE ANALYSIS OF SOUTH TEXAS ESTUARY WATERS�
32 COMPARISON OF PARTICLE COUNT ANALYSIS OF A CLEAN ROOM AND A 25�
STANDARD LABORATORY AT DUQUESNE UNIVERSITY IN PITTSBURGH, PA�
33 PARTICLE SIZE COMPARISON CHART FOR COMMON PARTICULATES 26� Appendix A SUMMARY OF UPDATES/CHANGES IN CHAPTER 3 � 27 � SW846 Update V THREE i Revision 5 � July 2014 �
INORGANIC ANALYTESPrior 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 SW846 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.
The following terms are relevant for the determination of inorganic analytes:
Calibration blank: The calibration blank is a sample of analytefree 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
Dissolved metals: The concentration of metals determined in an aqueous sample after the sample is filtered through a 0.45µm filter (see Method 3005).
Initial calibration verification (ICV) standard: A certified or independentlyprepared 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 (ICPOES) and inductively coupled plasma mass spectrometry (ICPMS) 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.
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 xaxis. The analyte concentration in the original unspiked sample is equal to the inverse of the x intercept. 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.
Spectral Interference Check solution (SIC): A solution containing both interfering and analyte elements of known concentration that can be used in ICPOES and ICPMS analysis to verify background and interelement correction factors.
Suspended metals: The concentration of metals determined in the portion of an aqueous sample that is retained by a 0.45µm filter (Method 3005).
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. 77206, 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. 2005149, 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
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 SW846 Update V THREE 4 Revision 5 July 2014 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 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.