1、Designation: D516 16Standard 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 U.S. Department of Defense.1. Scope*1.1 This turbidimetric test method covers the determinationof sulfate in water in t
3、he range 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 disco
4、ntinued. 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 responsib
5、ilityof 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 W
6、aterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4327 Test Method for Anions in Water by Suppressed IonChromatographyD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Wri
7、ting Quality Control Specificationsfor Standard Test Methods for Water AnalysisE60 Practice for Analysis of Metals, Ores, and RelatedMaterials by SpectrophotometryE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3. Terminology3.1 Definitions:3.1.1 Fo
8、r definitions of terms used in this standard, refer toTerminology D1129.4. Summary of Test Method4.1 Sulfate ion is converted to a barium sulfate suspensionunder controlled conditions.Asolution containing glycerin andsodium chloride is added to stabilize the suspension andminimize interferences. The
9、 resulting turbidity is determinedby a nephelometer, spectrophotometer, or photoelectric colo-rimeter and compared to a curve 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 exce
10、ss of about250 mg/L in drinking water, it causes a cathartic action(especially in children) in the presence of sodium andmagnesium, and gives a bad taste to the water.5.2 Test Method D4327 (“Test Method of Anions in Waterby Suppressed Ion Chromatography”) may be used.6. Interferences6.1 Insoluble su
11、spended 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 bariumsulfate precipitation causing a negative interference. Phospho-nates presen
12、t 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 excess of5000 mg/L will cause a negative interference. Aluminum,1This test meth
13、od 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 June 1, 2016. Published June 2016. Originallyapproved in 1938. Last previous edition approved in 2011 as D516 11. DOI:10.1520/
14、D0516-16.2For 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.*A Summary of Changes section appears at the end of
15、this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1polymers, and large quantities of organic material present inthe test sample may cause the barium sulfate to precipitatenonuniformly. In the presence of organic matter certa
16、in 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 found in water do notappear to interfere, the formation of the barium sulfate suspen-si
17、on 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 inorder of preference.7.1.1 Nephelometer or turbidimeter;7.1.2 Spectrophotometer for use at
18、 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 timer.7.3 Measuring Spoon, capacity 0.2 to 0.3 mL.7.4 Filter photometers and photometric pr
19、actices prescribedin this test method shall conform to Practice E60; spectropho-tometer practices shall conform to Practice E275.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform
20、 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 lessening the accuracy of the determination.8.2 Purity of WaterUnless oth
21、erwise 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 purity to permit its use without adverselyaffecting the precision and bi
22、as 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 crystals over a large watch glass, desiccatefor 24 h, screen to remove any
23、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 chloride(NaCl) in a container. Add 50 mL glycerol and mix.8.5 Sulfate Solut
24、ion, 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.8.6 Filter PaperPurchase suitable filter paper. Typicallythe filter papers have a pore
25、 size of 0.45-m membrane.Material such as fine-textured, acid-washed, ashless paper, orglass fiber paper are acceptable. The user must first ascertainthat the filter paper is of sufficient purity to use withoutadversely affecting the bias and precision of the test method.9. Sampling9.1 Collect the s
26、ample 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 in milligrams p
27、er 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 0.0, 5.0, 10.0,
28、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 curve with each s
29、eries of tests by running two ormore solutions of known sulfate concentrations.11. Procedure11.1 Filter (8.6) 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 between 0.
30、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 concentrat
31、ing 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 measuredspo
32、onful 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 period has end
33、ed, poursolution into the cell and measure the turbidity at 30-s intervalsfor 4 min. Record the maximum reading obtained in the 4-minperiod.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by
34、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. (USPC), Rockville,MD.D516 16211.7 If the sample contains color or turbidity, run a sampleblank usi
35、ng the procedure 11.2 through 11.6 without theaddition of the barium chloride.11.8 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 as
36、sumed to be absent.NOTE 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 sulfate ion
37、 (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 with the
38、 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 (drinking,gro
39、und, 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 collaborative
40、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 13, these precis
41、ion 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.14.2 Calibration and Calibration Verification:14.2.1 Analyze at
42、 least three working standards containingconcentrations of sulfate that bracket the expected sampleconcentration, prior to analysis of samples, to calibrate theinstrument (see Section 11). The calibration correlation coef-ficient shall be equal to or greater than 0.990.14.2.2 Verify instrument calib
43、ration after standardization byanalyzing a standard at the concentration of one of thecalibration standards. The concentration of a mid-range stan-dard should fall within 615% of the known concentration.Analyze a calibration blank to verify system cleanliness.14.2.3 If calibration cannot be verified
44、, recalibrate theinstrument.14.2.4 It is recommended to analyze a continuing calibra-tion blank (CCB) and continuing calibration verification(CCV) at a 10% frequency. The results should fall within theexpected precision of the method or + 15% of the knownconcentration.14.3 Initial Demonstration of L
45、aboratory Capability:4Supporting data are available from ASTM. Request RR:D-19-1145.TABLE 1 Overall (ST) and Single-Operator (SO) StandardDeviations Against Mean Concentration for InterlaboratoryRecovery of Sulfate from Reagent WaterAMean Concentration (x),mg/LStandard Deviation, mg/LSTSO6.6 0.5 0.1
46、20.4 1.0 0.463.7 2.5 1.3AThe test method is linear to 40 mg/L. Testing at the 63.9 level was accomplishedthrough dilution as described in 11.2.TABLE 2 Overall (ST) and Single-Operator (SO) StandardDeviations Against Mean Concentration for InterlaboratoryRecovery of Sulfate from Drinking, Ground, and
47、 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 was accomplishedthrough dilution as described in 11.2.TABLE 3 Determination of BiasAAmountAdded,mg/LAmountFound,mg/LBias % BiasSta
48、tisticallySignificantat 5 %Level (at0.05)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 %nononoAThe test method is linear to 40 mg/L. Testing at the 63.9 level was accomplishedthrough dilution as des
49、cribed in 11.2.TABLE 4 Mean Sulfate Recovery Against Concentration Addedwith Overall Standard Deviation Shown for InterlaboratoryExperimental Recovery of Sulfate from Reagent Waterand Drinking, Ground, 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 was accomplishedthrough dilution as described in 11.2.D516 16314.3.1 If a laboratory has no
