SOUTH AFRICAN NATIONAL STANDARD. Standard test methods for lead in water

Transcription

1 ISBN Edition 1 SOUTH AFRICAN NATIONAL STANDARD Standard test methods for lead in water This national standard is the identical implementation of ASTM D 559:200 and is adopted with the permission of ASTM International. Published by Standards South Africa 1 dr lategan road groenkloof private bag x191 pretoria 0001 tel: fax: international code Standards South Africa

2 Edition 1 Table of changes Change No. Date Scope National foreword This South African standard was approved by National Committee StanSA SC A, Water Water sampling and analysis, in accordance with procedures of Standards South Africa, in compliance with annex of the WTO/TBT agreement. This SANS document was published in June 2007.

3 Designation: D Standard Test Methods for Lead in Water 1 This standard is issued under the fixed designation D 559; 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 (e) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. 1. Scope* 1.1 These test methods cover the determination of dissolved and total recoverable lead in water and waste water by atomic-absorption spectrophotometry 2 and differential pulse anodic stripping voltammetry. Four test methods are included as follows: Concentration Range Sections Test Method A Atomic Absorption, Direct 1.0 to 10 7 to 15 Test Method B Atomic Absorption, 100 to 1000 µg/l 16 to 24 Chelation-Extraction Test Method C Differential Pulse Anodic 1to100µg/L 25to5 Stripping Voltammetry Test Method D Atomic Absorption, Graphite Furnace 5to100µg/L 6to Test Method B can be used to determine lead in brines. Test Method D has been used successfully with reagent water, lake water, well water, filtered tap water, condensate from a medium Btu coal gasification process, waste treatment plant effluent, and a production plant process water. 1. It is the user s responsibility to ensure the validity of these test methods for waters of untested matrices. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards statements, see , Note 2, 11.2, 11., 21.7, 21.8, 21.11, 2.7, 2.10, 2.2.1, and Referenced Documents 2.1 ASTM Standards: D 858 Test Methods for Manganese in Water 1 These test methods are under the jurisdiction of ASTM Committee D19 on Water and are the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water. Current edition approved Jan. 10, 200. Published January 200. Originally approved in Last previous edition approved in 1996 as D Platte, J. A., and Marcy, V. M., A New Tool for the Water Chemist, Industrial Water Engineering, May Brown, E., Skougstad, M. W., and Fishman, M. J., Methods for Collection and Analysis of Water Samples for Dissolved Minerals and Gases, Techniques of Water-Resources Investigations of the U. S. Geological Survey, Book 5, Chapter, 1970, p Annual Book of ASTM Standards, Vol D 1066 Practice for Sampling Steam D 1068 Test Methods for Iron in Water D 1129 Terminology Relating to Water D 1192 Specification for Equipment for Sampling Water and Steam in Closed Conduits D 119 Specification for Reagent Water D 1687 Test Methods for Chromium in Water D 1688 Test Methods for Copper in Water D 1691 Test Methods for Zinc in Water D 1886 Test Methods for Nickel in Water D 2777 Practice for Determination of Precision and Bias of Applicable Methods of Committee D-19 on Water D 70 Practices for Sampling Water from Closed Conduits D 557 Test Methods for Cadmium in Water D 558 Test Methods for Cobalt in Water D 919 Practice for Measuring Trace Elements in Water by Graphite Furnace Atomic Absorption Spectrophotometry D 4841 Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic Constituents D 5810 Guide for Spiking into Aqueous Samples D 5847 Practice for the Writing Quality Control Specifications for Standard Test Methods for Water Analysis E 60 Practice for Photometric and Spectrophotometric Methods for Chemical Analysis of Metals 4 E 275 Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near Infrared Spectrophotometers 5. Terminology.1 Definitions For definition of terms used in these test methods, refer to Terminology D total recoverable lead an arbitrary analytical term relating to the recoverable forms of lead that are determined by the digestion method which are included in the procedure. 4. Significance and Use 4.1 The test for lead is necessary because it is a toxicant and because there is a limit specified for lead in potable water in the National Interim Primary Drinking Water Regulations. This 4 Annual Book of ASTM Standards, Vol Annual Book of ASTM Standards, Vol *A Summary of Changes section appears at the end of this standard. Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA , United States. 1

4 D559 0 test serves to determine whether the lead content of potable water is above or below the acceptable limit. 5. Purity of Reagents 5.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society. 6 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination. 5.2 Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to Specification D 119, Type I. Other reagent water types may be used provided it is first ascertained that the water is of sufficiently high purity to permit its use without adversely affecting the bias and precision of the test method. Type II water was specified at the time of round-robin testing of this test method. 6. Sampling 6.1 Collect the samples in accordance with Practice D 1066, Specification D 1192, and Practices D 70, as applicable. 6.2 Samples shall be preserved with HNO (sp gr 1.42) to a ph of 2 or less immediately at the time of collection, normally about 2 ml/l of HNO. If only dissolved lead is to be determined, the sample shall be filtered through a 0.45-µm membrane filter before acidification. TEST METHOD A ATOMIC ABSORPTION, DIRECT 7. Scope 7.1 This test method covers the determination of dissolved and total recoverable lead in most waters and wastewaters. 7.2 The test method is applicable in the range from 1.0 to 10 of lead. The upper limits of detectability can be increased to concentrations greater than 10 by dilution of the sample. 8. Summary of Test Method 8.1 Lead is determined by atomic absorption spectrophotometry. Dissolved lead is determined by aspirating the filtered and preserved sample directly with no pretreatment. Total recoverable lead is determined by aspirating the sample following hydrochloric-nitric acid digestion and filtration. The same digestion procedure may be used to determine total recoverable cadmium (Test Methods D 557), chromium (Test Methods D 1687), cobalt (Test Methods D 558), copper (Test Methods D 1688), iron (Test Methods D 1068), manganese (Test Methods D 858), nickel (Test Methods D 1886), and zinc (Test Methods D 1691). 6 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD. 9. Interferences 9.1 Other metals usually do not interfere in the determination of lead by increasing or decreasing the amount of absorbed radiation. The most common interference is caused by a chemical reaction in the flame that prevents conversion of the lead to the atomic state. 9.2 High concentrations of calcium, such as those connected with the coal industry, will give lead concentrations higher than which actually exist. This can be corrected by using a background correction technique, or by the chelation-extraction procedure (Test Method B) The equipment manufacturer s instructions for use of specific correction technique shall be followed. 10. Apparatus 10.1 Atomic Absorption Spectrophotometer, for use at 28. nm. NOTE 1 The manufacturer s instructions shall be followed for all instrumental parameters. Wavelengths other than 28. nm may be used if they have been determined to be equally suitable Lead Light Source, hollow-cathode lamps or electrodeless-discharge lamps have been found satisfactory. 10. Oxidant: Air, which has been passed through a suitable filter to remove oil, water, and other foreign substances, is the usual oxidant Fuel: Acetylene Standard, commercially available acetylene is the usual fuel. Acetone, always present in acetylene cylinders, can affect analytical results. The cylinder should be replaced at 50 psig (45 kpa) Warning Purified grade acetylene containing a special proprietary solvent rather than acetone should not be used with poly(vinyl chloride) tubing as weakening of the walls can cause a potential hazardous situation Pressure-Reducing Valves The supplies of fuel and oxidant shall be maintained at pressures somewhat higher than the controlled operating pressure of the instrument by suitable valves. 11. Reagents 11.1 Hydrochloric Acid (sp gr 1.19) Concentrated hydrochloric acid (HCl). NOTE 2 If the reagent blank concentration is greater than the method detection limit, distill the HCl or use a spectrograde acid. Caution When HCl is distilled, an azeotropic mixture is formed (approximately 6 N HCl is formed). Therefore, whenever concentrated HCl is used in the preparation of a reagent or in the procedure, use double the volume specified if distilled HCl is used Lead Solution, Stock (1 ml = 1 mg lead) Dissolve g of lead nitrate (Pb (NO ) 2 ) in a mixture of 10 ml of HNO (sp gr 1.42) and 100 ml of water. Dilute to 1 L with water. Warning Lead salts are toxic. Handle with care and avoid personal contamination. 11. Lead Solution, Standard (1 ml = 0.1 mg lead) Dilute ml of stock lead solution to 1 L with HNO ( ). Store all solutions in polyethylene bottles. Warning Lead 2

5 D559 0 salts are toxic. Never pipet by mouth. Pipet with the end of a suction device or employ other conventional means of quantitative measurement Nitric Acid (sp gr 1.42) Concentrated nitric acid (HNO ). NOTE If the reagent blank concentration is greater than the method detection limit, distill the HNO or use a trace metal grade acid Nitric Acid ( ) Add 1 volume of HNO (sp gr 1.42) to 499 volumes of water. 12. Standardization 12.1 Prepare 100 ml each of a blank and at least four standard solutions to bracket the expected lead concentration range to be analyzed by diluting the lead standard solution (11.) with HNO ( ). Prepare the standards each time the test is to be performed When determining total recoverable lead, add 0.5 ml of HNO (sp gr 1.42) to each blank and standard solution and proceed as directed in 1.2 through 1.4. After the digestion of the blank and standard solutions has been completed in 1.4, return to 12. to complete the standardization for total recoverable determinations. When determining dissolved lead, proceed with Aspirate the blank and standards and record the instrument readings. Aspirate HNO ( ) between standards Prepare an analytical curve by plotting the absorbance versus the concentration for each standard on linear graph paper. Alternatively, read directly in concentration if this capability is provided with an instrument. 1. Procedure 1.1 Measure ml of a well-mixed acidified sample into a 125-mL beaker or flask. NOTE 4 If only dissolved lead is to be determined, start with Add 5 ml of HCl (sp gr 1.19) to each sample. 1. Heat the samples on a steam bath or hot plate in a well-ventilated hood until the volume has been reduced to 15 to 20 ml, making certain that the samples do not boil. NOTE 5 For samples having appreciable amounts of suspended matter or dissolved matter, the amount of reduction in volume is left to the discretion of the analyst. 1.4 Cool and filter the samples through a suitable filter such as fine-textured, acid washed, ashless paper, into 100-mL volumetric flasks. Wash the filter paper two or three times with water and adjust to volume. 1.5 Aspirate each filtered and acidified sample and determine its absorbance or concentration at 28. nm. Aspirate HNO ( ) between samples. 14. Calculation 14.1 Calculate the concentration of lead in each sample, in milligrams per litre, using the calibration curve established in Amount Added, TABLE 1 Determination of Bias, Direct Amount Found, S T, S 0, Bias, % Statistically Significant (95 % Confidence Level) Reagent Water, Type II no no no Selected Water Matrices no yes no 15. Precision and Bias Fourteen operators from nine laboratories participated in this study. One operator performed the analysis in quadruplicate, twelve in triplicate and one in duplicate at each concentration level The bias of this test method for lead is listed in Table These data may not apply to waters of other matrices This section on precision and bias conforms to Practice D which was in place at the time of collaborative testing. Under the allowances made in 1.4 of D , these precision and bias data do meet existing requirements of interlaboratory studies of Committee D19 test methods. 16. Quality Control 16.1 In order to be certain that analytical values obtained using these test methods are valid and accurate within the confidence limits of the test, the following QC procedures must be followed when analyzing lead Calibration and Calibration Verification: Analyze at least three working standards containing concentrations of lead that bracket the expected sample concentration, prior to analysis of samples, to calibrate the instrument. The calibration correlation coefficient shall be equal to or greater than In addition to the initial calibration blank, a calibration blank shall be analyzed at the end of the batch run to ensure contamination was not a problem during the batch analysis Verify instrument calibration after standardization by analyzing a standard at the concentration of one of the calibration standards. The concentration of a mid-range standard should fall within 615 % of the known concentration If calibration cannot be verified, recalibrate the instrument. 16. Initial Demonstration of Laboratory Capability: If a laboratory has not performed the test before, or if there has been a major change in the measurement system, for example, new analyst, new instrument, etc., a precision and bias study must be performed to demonstrate laboratory capability. 7 Supporting data are available from ASTM Headquarters. Request RR:D