1、Designation: D3920 02 (Reapproved 2007)1D3920 12Standard Test Method forStrontium in Water1This standard is issued under the fixed designation D3920; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb
2、er in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEEditorial changes were made throughout in September 2007.1. Scope Scope*1.1 This test method covers the determination of dissolved and total reco
3、verable strontium in water and wastewater by atomicabsorption spectroscopy.1.2 The test method is applicable in the range from 0.1 to 1 mg/L of strontium. The range may be extended by dilution of theoriginal sample.1.3 Round-robin data were obtained in natural and reagent water matrices. It is the u
4、sers responsibility to ensure the validityof the test method for waters of untested matrices.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem are mathematical conversions and may not be exact equivalents; therefor
5、e, each system shall be used independently of theother.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability
6、of regulatorylimitations prior to use. Specific precautionary statements are given in 8.4 and 8.9.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Co
7、mmittee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4691 Practice for Measuring Elements in Water by Flame Atomic Absorption SpectrophotometryD4841 Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic ConstituentsD5810 Guide for Spiking i
8、nto Aqueous SamplesD5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis3. Terminology3.1 Definitions: For definitions of terms used in this test method, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 total recover
9、able strontium, nan arbitrary analytical term relating to the forms of strontium that are determinable by thedigestion procedure described in this test method.3.2.2 laboratory control sample, na solution with a certified concentration of the strontium.4. Summary of Test Method4.1 Strontium is determ
10、ined by atomic absorption spectrophotometry. The sample is aspirated into an air-acetylene flamefollowing the addition of lanthanum chloride/potassium chloride solution. Samples containing particulate matter that may clog theaspirator capillary or burner, thus producing inaccurate results, are filte
11、red through a 0.45-m membrane filter prior to testing.1 This test method is under the jurisdiction ofASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.Current edition approved Aug. 1, 2007Sept. 1, 2012. Published September 2007 Sep
12、tember 2012. Originally approved in 1980. Last previous edition approved in 2002as D3920 02.D3920 02(2007)E01. DOI: 10.1520/D392002R07E0110.1520/D3920122 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Sta
13、ndardsvolume information, refer to the standards Document Summary page on the ASTM website. DOI: 10.1520/D3920-02R07E01.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit m
14、ay not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at t
15、he end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 Although most potable supplies contain little strontium, some well waters in the midwestern part of the United States havelevels as high
16、 as 39 mg/L.35.2 This test method affords a reliable means of accurately determining strontium and correcting calcium results obtained bythe methods cited in 6.2.6. Interferences6.1 Chemical interference caused by silicon, aluminum, and phosphate is controlled by adding lanthanum chloride. Potassium
17、chloride is added to suppress the ionization of strontium.NOTE 1A nitrous oxide-acetylene flame has been used successfully by some to remove chemical interferences.6.2 Strontium chemically resembles calcium and causes a positive error in gravimetric and titrimetric methods for calciumdetermination.7
18、. Apparatus7.1 Atomic Absorption Spectrophotometer for use at 460.7 nm. A general guide for the use of flame atomic absorptionapplications is given in Practice D4691.NOTE 2The manufacturers instructions should be followed for setting instrumental parameters.7.2 Strontium Hollow-Cathode Lamp.8. Reage
19、nts and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are available.
20、 4 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently highpurity to permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, reference to water shall be understood to mean reagent water conforming to
21、Specification D1193, Type I, II, and III water. Type I is preferred and more commonly used. Other reagent water types may be usedprovided it is first ascertained that the water is of sufficiently high purity to permit its use without adversely affecting the precisionand bias of the test method. Type
22、 II water was specified at the time of round robin testing of this test method.NOTE 3The user must ensure the type of reagent water chosen is sufficiently free of interferences.The water should be analyzed using the test method.8.3 Hydrochloric Acid (sp gr 1.19)Concentrated hydrochloric acid (HCl).8
23、.4 Lanthanum Chloride/Potassium Chloride SolutionDissolve 11.73 g of lanthanum oxide (La2O3) in a minimum amount ofconcentrated hydrochloric acid (approximately 50 mL.). Add 1.91 g of potassium chloride (KCl). Allow solution to cool to roomtemperature and dilute to 100 mL with water. (WarningAdd aci
24、d slowly and in small portion to control the reaction rate uponmixing.)8.5 Nitric Acid (sp gr 1.42)Concentrated HNO3.8.6 Strontium Solution, Stock (1.0 mL = 1.0 mg Sr)Dissolve 2.415 g of strontium nitrate (Sr(NO3)2) in a 1-L flask containing10 mL of concentrated HCl and 700 mL of water. Dilute to 10
25、00 mL with water. A purchased strontium stock solution ofappropriate known purity is also acceptable.8.7 Strontium Solution, Standard (1 mL = 0.010 mg Sr)Dilute 5.0 mL of strontium solution standard to 500 mL with water.8.8 OxidantAir that has been cleaned and dried through a suitable filter to remo
26、ve oil, water, and other foreign substances,is the usual oxidant.8.9 FuelStandard, commercially available acetylene is the usual fuel. Acetone, always present in acetylene cylinders, can beprevented from entering the burner system by replacing the cylinder when the pressure reaches 490 kPa (70 psig)
27、.(WarningPurified grade acetylene containing a special proprietary solvent other than acetone should not be used with poly(vinyl chloride) tubing as weakening of the walls may result and cause a potentially hazardous situation.)9. Sampling9.1 Collect the samples in accordance with instructions in Pr
28、actices D3370. The holding time for the samples may be calculatedin accordance with Practice D4841.3 Standard Method for the Examination of Water and Wastewater, 14th Ed. American Public Health Assn., Washington, DC 20005.4 Reagent Chemicals, American Chemical Society Specifications, American Chemic
29、al Society, Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockv
30、ille, MD.D3920 1229.2 To preserve the samples add concentrated HNO3 (sp gr 1.42) to a pH of 2 or less immediately at the time of collection;normally about 2 mL/L is required. If only dissolved strontium is to be determined, filter the samples at time of collection througha 0.45-m membrane filter bef
31、ore acidification.NOTE 4Alternatively, the pH may be adjusted in the laboratory if the sample is returned within 14 days. This could reduce hazards of working withacids in the field when appropriate.10. Standardization10.1 Prepare a blank and at least four working standards to bracket the expected s
32、trontium concentration range of the samplesto be analyzed by diluting the standard strontium solution (8.6) to the desired concentrations. Select concentrations that will givea zero, middle, and maximum points for the analytical curve.10.2 Pipette 10.0 mL of each standard into a 50-mL beaker or flas
33、k and add 1.0 mL of lanthanum chloride/potassium chloridesolution. Mix well by swirling.10.3 To test the suitability of reagents used in the analysis, zero the instrument while aspirating reagent water.Aspirate the zerostandard and record the response. If the zero standard produces a response suffic
34、ient to affect the detection limit or accuracy, orboth, of the test method, the contaminated reagent should be identified and replaced with a grade of suitable quality beforeproceeding.10.4 Aspirate the blank (zero standard) and adjust the instrument reading to zero. Aspirate standards and record th
35、e instrumentreading for each. Aspirate reagent water between each standard.NOTE 5Best results have been obtained with a slightly fuel rich flame.10.5 Construct an analytical curve by plotting the absorbance of standards versus milligrams of strontium per litre.Alternatively,read directly in concentr
36、ation if this capability is provided in the instrument.11. Procedure11.1 For total recoverable strontium, add 5 mL of concentrated nitric acid (8.5) to 100 mL of the sample in a 250-mLErlenmeyer flask, and mix well. Heat the sample at 95C on a steam bath/hot plate in a well-ventilated fume hood unti
37、l the volumeis reduced to 15 to 20 mL.NOTE 6When testing samples of brine or samples containing a large amount of solids, the amount of reduction in volume is left to the discretionof the analyst.NOTE 7Many laboratories have found block digestion systems a useful way to digest samples for trace meta
38、ls analysis. Systems typically consist ofeither a metal or graphite block with wells to hold digestion tubes. The block temperature controller must be able to maintain uniformity of temperatureacross all positions of the block. For trace metals analysis, the digestion tubes should be constructed of
39、polypropylene and have a volume accuracy ofat least 0.5%. All lots of tubes should come with a certificate of analysis to demonstrate suitability for their intended purpose.11.2 If color in the digested solution indicates the presence of partially oxidized materials, add additional nitric acid andap
40、proximately 90 mL of reagent water to the cooled solution and repeat the digestion as before. Repeat this step several times ifnecessary.11.3 Cool and filter the digested solution through a suitable filter (such as fine-textured, acid-washed ashless paper) into a100-mL volumetric flask. Wash the fil
41、ter paper 2 to 3 times and make up to volume with reagent water. A reagent blank (100 mLof reagent water and 5 mL of concentrated nitric acid) should be carried through the digestion process and treated as instructedin 10.3. An unacceptable high response could indicate that the nitric acid was of po
42、or quality.NOTE 8If only dissolved strontium is to be determined, filter portion of the sample through a 0.45-m membrane filter and proceed with 11.4.11.4 Pipette 10.0 mL of sample, or a dilution of the sample, into a 50-mL beaker or flask.11.5 Add 1.0 mL of lanthanum chloride/potassium chloride sol
43、ution (8.4) to each sample. Mix well by swirling.11.6 Aspirate each sample and record its absorbance or concentration. Aspirate reagent water between each sample.11.7 For instruments that do not readout directly in concentration, determine the strontium concentration of the aspiratedsolution from th
44、e analytical curve (10.5).12. Calculation12.1 Where dilutions have been made, calculate the concentration of strontium in the original sample as follows:Sr,mg/L5A 3BCwhere:A = Sr read from the analytical curve (10.5), mg/L,B = total final volume of the diluted sample, andD3920 123C = volume of origi
45、nal sample diluted.13. Precision and Bias513.1 The overall precision (reagent and waters of choice) and the single-operator precision for reagent water, based on data fromeight participating laboratories involving twelve operators, varies with the quantity measured within the designated range of the
46、test method as shown in Fig. 1.13.2 The single-operator precision for waters of choice can be defined by the expression 0.023 S o 0.026, with the meanprecision value of 0.024 mg/L over the designated range.13.3 Recoveries of known amounts of strontium in a series of prepared standards were as given
47、in Table 1.13.4 This test method was evaluated with reagent and natural water matrices. These data may not apply to waters of othermatrices.13.5 Precision and bias for this test method conforms to Practice D2777 77, which was in place at the time of collaborativetesting. Under the allowances made in
48、 1.4 of D2777 06, 08, these precision and bias data do meet existing requirements forinterlaboratory studies of Committee D19 test methods.5 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D19-1054.FIG. 1 Interlaboratory Precisi
49、on for Strontium in WaterD3920 124NOTE 9The nitric acid digestion steps were not performed in the round-robin of this test method. It is an approved, recommended practice fordetermining total recoverable metals by atomic absorption spectrometry; however, its use can be expected to increase the variability of final results. Theuser should verify its suitability for a matrix of interest by evaluating recovery for spikes that have been taken through the digestion process (GuideD5810).14. Quality Control (QC)14.1 The following quality c
