1、Designation: D516 11Standard Test Method forSulfate Ion in Water1This standard is issued under the fixed designation D516; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates
2、 the year of last reapproval. Asuperscript epsilon () 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 This turbidimetric test method covers the determinationof sulfate in water in the ra
3、nge from 5 to 40 mg/Lof sulfate ion(SO4).1.2 This test method was used successfully with drinking,ground, and surface waters. It is the users responsibility toensure the validity of this test method for waters of untestedmatrices.1.3 Former gravimetric and volumetric test methods havebeen discontinu
4、ed. Refer to Appendix X1 for historical infor-mation.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibility
5、of the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD
6、2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE60 Practice for Analysis of Metals, Or
7、es, and RelatedMaterials by SpectrophotometryE275 Practice for Describing and Measuring Performanceof Ultraviolet and Visible Spectrophotometers3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D1129.4. Summary of Test Method4.1 Sulfate ion is conver
8、ted to a barium sulfate suspensionunder controlled conditions.Asolution containing glycerin andsodium chloride is added to stabilize the suspension andminimize interferences. The resulting turbidity is determinedby a nephelometer, spectrophotometer, or photoelectric colo-rimeter and compared to a cu
9、rve prepared from standard sulfatesolutions.5. Significance and Use5.1 The determination of sulfate is important because it hasbeen reported that when this ion is present in excess of about250 mg/L in drinking water, it causes a cathartic action(especially in children) in the presence of sodium and
10、magne-sium, and gives a bad taste to the water.6. Interferences6.1 Insoluble suspended matter in the sample must beremoved. Dark colors that cannot be compensated for in theprocedure interfere with the measurement of suspended bariumsulfate (BaSO4).6.2 Polyphosphates as low as 1 mg/L will inhibit ba
11、riumsulfate precipitation causing a negative interference. Phospho-nates present in low concentrations, depending on the type ofphosphonate, will also cause a negative interference. Silica inexcess of 500 mg/L may precipitate along with the bariumsulfate causing a positive interference. Chloride in
12、excess of1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Sept. 1, 2011. Published September 2011. Originallyapproved in 1938. Last previous edition approved in
13、 2007 as D516 07. DOI:10.1520/D0516-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes
14、 section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5000 mg/L will cause a negative interference. Aluminum,polymers, and large quantities of organic material present inthe test sample may cause
15、 the barium sulfate to precipitatenonuniformly. In the presence of organic matter certain bacte-ria may reduce sulfate to sulfide. To minimize the action ofsulfate reducing bacteria, samples should be refrigerated at 4Cwhen the presence of such bacteria is suspected.6.3 Although other ions normally
16、found in water do notappear to interfere, the formation of the barium sulfate suspen-sion is very critical. Determinations that are in doubt may bechecked by a gravimetric method in some cases, or by theprocedure suggested in Note 2.7. Apparatus7.1 PhotometerOne of the following which are given inor
17、der of preference.7.1.1 Nephelometer or turbidimeter;7.1.2 Spectrophotometer for use at 420 nm with light path of4to5cm;7.1.3 Filter photometer with a violet filter having a maxi-mum near 420 nm and a light path of 4 to 5 cm.7.2 Stopwatch, if the magnetic stirrer is not equipped withan accurate time
18、r.7.3 Measuring Spoon, capacity 0.2 to 0.3 mL.7.4 Filter photometers and photometric practices prescribedin this test method shall conform to Practice E60; spectropho-tometer practices shall conform to Practice E275.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.
19、Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society.3Other grades may be used, provided it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout
20、lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Specification D1193, Type I. Other reagent water types maybe used provided it is first ascertained that the water is ofsufficiently high
21、 purity to permit its use without adverselyaffecting the precision and bias of the test method. Type IIwater was specified at the time of round robin testing of thistest method.8.3 Barium ChlorideCrystals of barium chloride(BaCl22H2O) screened to 20 to 30 mesh. To prepare in thelaboratory, spread cr
22、ystals over a large watch glass, desiccatefor 24 h, screen to remove any crystals that are not 20 to 30mesh, and store in a clean, dry jar.8.4 Conditioning ReagentPlace 30 mL of concentratedhydrochloric acid (HCl, sp gr 1.19), 300 mLreagent water, 100mL 95 % ethanol or isopropanol and 75 g sodium ch
23、loride(NaCl) in a container. Add 50 mL glycerol and mix.8.5 Sulfate Solution, Standard (1 mL = 0.100 mg SO4)Dissolve 0.1479 g of anhydrous sodium sulfate (Na2SO4)inwater, and dilute with water to 1 L in a volumetric flask. Apurchased stock solution of adequate purity is also acceptable.9. Sampling9.
24、1 Collect the sample in accordance with Practice D1066,and Practices D3370, as applicable.10. Calibration10.1 Follow the procedure given in Section 11, usingappropriate amounts of the standard sulfate solution preparedin accordance with 8.5 and prepare a calibration curve showingsulfate ion content
25、in milligrams per litre plotted against thecorresponding photometer readings (Note 1). Prepare standardsby diluting with water 0.0, 5.0, 10.0, 15.0, 20.0, 30.0, and 40.0mL of standard sulfate solution to 100-mL volumes in volu-metric flasks. These solutions will have sulfate ion concentra-tions of 0
26、.0, 5.0, 10.0, 15.0, 20.0, 30.0, and 40.0 mg/L (ppm),respectively.NOTE 1A separate calibration curve must be prepared for eachphotometer and a new curve must be prepared if it is necessary to changethe cell, lamp, or filter, or if any other alterations of instrument or reagentsare made. Check the cu
27、rve with each series of tests by running two ormore solutions of known sulfate concentrations.11. Procedure11.1 Filter the sample if it is turbid through a 0.45-mmembrane and adjust the temperature to between 15 and 30C.11.2 Pipette into a 250-mL beaker 100 mL or less of theclear sample containing b
28、etween 0.5 and 4 mg of sulfate ion(Note 2). Dilute to 100 mL with water if required, and add 5.0mL of conditioning reagent (Note 1).NOTE 2The solubility of BaSO4is such that difficulty may beexperienced in the determination of sulfate concentrations below about 5mg/L (ppm). This can be overcome by c
29、oncentrating the sample or byadding 5 mL of standard sulfate solution (1 mL = 0.100 mg SO4)tothesample before diluting to 100 mL. This will add 0.5 mg SO4to the sample,which must be subtracted from the final result.11.3 Mix in the stirring apparatus.11.4 While the solution is being stirred, add a me
30、asuredspoonful of BaCl2crystals (0.3 g) and begin timing immedi-ately.11.5 Stir exactly 1.0 min at constant speed.NOTE 3The stirring should be at a constant rate in all determinations.The use of a magnetic stirrer has been found satisfactory for this purpose.11.6 Immediately after the stirring perio
31、d has ended, poursolution into the cell and measure the turbidity at 30-s intervalsfor 4 min. Record the maximum reading obtained in the 4-minperiod.11.7 If the sample contains color or turbidity, run a sampleblank using the procedure 11.2 through 11.6 without theaddition of the barium chloride.11.8
32、 If interferences are suspected, dilute the sample with anequal volume of water, and determine the sulfate concentrationagain. If the value so determined is one half that in theundiluted sample, interferences may be assumed to be absent.3Reagent Chemicals, American Chemical Society Specifications, A
33、mericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (
34、USPC), Rockville,MD.D516 112NOTE 4After dilution, if interferences are still determined to bepresent alternate methods should be used. It is up to the user to determineappropriate alternate methods.12. Calculation12.1 Convert the photometer readings obtained with thesample to milligrams per litre su
35、lfate ion (SO4) by use of thecalibration curve described in Section 10.13. Precision and Bias413.1 The precision and bias data presented in this testmethod meet the requirements of Practice D2777 86.13.2 The overall and single-operator precision of the testmethod, within its designated range, varies
36、 with the quantitybeing tested according to Table 1 for reagent water and Table2 for drinking, ground, and surface waters.13.2.1 Seven laboratories participated in the round robin atthree levels in triplicate, making a total of 21 observations ateach level for reagent water and for matrix water (dri
37、nking,ground, and surface water).13.3 Recoveries of known amounts of sulfate from reagentwater and drinking, ground, and surface waters are as shown inTable 3.13.3.1 A table for estimating the bias of the test methodthrough its applicable concentration range can be found inTable 4.13.3.2 These colla
38、borative test data were obtained on re-agent grade water and natural waters. For other matrices, thesedata may not apply.13.4 Precision and bias for this test method conforms toPractice D2777 86, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofD2777 08, the
39、se precision and bias data do meet existingrequirements for interlaboratory studies of Committee D19 testmethods.14. Quality Control (QC)14.1 The following quality control information is recom-mended for the determination of sulfate ion in water.14.1.1 The instrument should be calibrated using a min
40、i-mum of four calibration standards and a calibration blank. Thecalibration correlation coefficient shall be equal to or greaterthan 0.990. In addition to the initial calibration blank, acalibration blank should be analyzed at the end of the batch runto ensure contamination was not a problem during
41、the batchanalysis.14.1.2 An instrument check standard should be analyzed ata minimum frequency of 10 % throughout the batch analysis.The value of the instrument check standard should fall between80 and 120 % of the true value.14.1.3 Two method blanks should be prepared ensuring thatan adequate metho
42、d blank volume is present for a minimum ofseven repetitive analyses.The standard deviation of the methodblank is used to determine the minimum detectable concentra-tion of each sample and control in the batch.14.1.4 A laboratory control sample should be analyzed witheach batch of samples at a minimu
43、m frequency of 10 %.14.1.5 If the QC for the sample batch is not within theestablished control limits, reanalyze the samples or qualify theresults with the appropriate flags, or both (See Practice D5847).14.1.6 Blind control samples should be submitted by anoutside agency in order to determine the l
44、aboratory perfor-mance capabilities.15. Keywords15.1 drinking water; ground water; sulfate; surface water;turbidimetric4Supporting data are available from ASTM. Request RR:D-19-1145.TABLE 1 Overall (ST) and Single-Operator (SO) StandardDeviations Against Mean Concentration for InterlaboratoryRecover
45、y of Sulfate from Reagent WaterAMean Concentration (x),mg/LStandard Deviation, mg/LSTSO6.6 0.5 0.120.4 1.0 0.463.7 2.5 1.3AThe test method is linear to 40 mg/L. Testing at the 63.9 level wasaccomplished through dilution as described in 11.2.TABLE 2 Overall (ST) and Single-Operator (SO) StandardDevia
46、tions Against Mean Concentration for InterlaboratoryRecovery of Sulfate from Drinking, Ground, and Surface WaterAMean Concentration (x),mg/LStandard Deviation, mg/LSTSO6.9 0.7 0.520.2 2.2 1.863.3 4.5 1.6AThe test method is linear to 40 mg/L. Testing at the 63.9 level wasaccomplished through dilution
47、 as described in 11.2.TABLE 3 Determination of BiasAAmountAdded,mg/LAmountFound,mg/L6Bias 6% BiasStatisticallySignificantat 5 %Level (at60.05)Reagent water 20.863.9A7.020.463.7A6.60.40.20.41.9 %0.2 %5.3 %nononoDrinking, groundand surface water20.863.9A7.020.263.3A6.90.60.60.12.7 %0.9 %1.8 %nononoATh
48、e test method is linear to 40 mg/L. Testing at the 63.9 level wasaccomplished through dilution as described in 11.2.TABLE 4 Mean Sulfate Recovery Against Concentration Addedwith Overall Standard Deviation Shown for InterlaboratoryExperimental Recovery of Sulfate from Reagent Waterand Drinking, Groun
49、d, and Surface WaterASulfate Added,mg/LMean Sulfate Recovery (x), mg/LReagent Water ( ST) Matrix Water ( SO)7.0 6.6 (0.5) 6.9 (0.7)20.8 20.4 (1.0) 20.2 (2.2)63.9 63.7 (2.5) 63.3 (4.5)AThe test method is linear to 40 mg/L. Testing at the 63.9 level wasaccomplished through dilution as described in 11.2.D516 113APPENDIX(Nonmandatory Information)X1. RATIONALE FOR DISCONTINUATION OF METHODSX1.1 Gravimetric:X1.1.1 This test method was discontinued in 1988. The testmethod may be found in the 1988 Annual Book of ASTMStandards, Vol 11.01. The te
