1、Designation: D4193 08 (Reapproved 2013)1Standard Test Method forThiocyanate in Water1This standard is issued under the fixed designation D4193; 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
2、parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEWarning notes were editorially updated throughout in June 2013.1. Scope1.1 This test method covers the quantitative colorimetriclaboratory measurement o
3、f dissolved thiocyanate in water,waste water, and saline water in the range from 0.1 to 2.0 mg/L.For higher concentrations, use an aliquot from the dilutedsample.1.1.1 ValidationThis test method was validated over therange of 0.07 to 1.42 mg/L. This test method was validated atnine laboratories at f
4、our levels. This test method may be validfor reporting results down to lower levels as validated inindividual user laboratories.1.1.2 ApplicationThis test method has been validated inreagent water, Type II, in multiple laboratories and 7 naturalwaters, 1 laboratory effluent, 1 steel mill effluent, a
5、nd 2dechlorinated and treated sanitary effluents in single laborato-ries. It is the users responsibility to assure the validity of thetest method on any untested matrices.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 T
6、his standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazard
7、statements, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Conduits (Withdrawn 2003)3D1193 Specification for Reagent WaterD2036 Test Methods for Cyanides in WaterD2777 Practice for Determinat
8、ion of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD4210 Practice for Intralaboratory Quality Control Proce-dures and a Discussion on Reporti
9、ng Low-Level Data(Withdrawn 2002)3D4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5788 Guide for Spiking Organics into Aqueous SamplesD5789 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Organic Constituen
10、ts(Withdrawn 2002)3D5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisD7237 Test Method for Free Cyanide with Flow InjectionAnalysis (FIA) Utilizing Gas Diffusion Separation andAmperometric DetectionD7365 Practice for Sampling, Preservation and Mitig
11、atingInterferences in Water Samples for Analysis of CyanideE60 Practice for Analysis of Metals, Ores, and RelatedMaterials by SpectrophotometryE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3. Terminology3.1 DefinitionsFor definitions of terms used
12、 in this testmethod, refer to Terminology D1129.4. Summary of Test Method4.1 This test method consists of thiocyanate reacting withferric ions at a pH of2toform a colored complex which isdetermined colorimetrically at 460 nm and adheres to BeersLaw.1This test method is under the jurisdiction of ASTM
13、 Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved June 1, 2013. Published July 2013. Originally approvedin 1982. Last previous edition approved in 2008 as D4193 08. DOI: 10.1520/D4193-08R13.2F
14、or 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.3The last approved version of this historical standard is refer
15、enced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 Industrial wastes may be highly colored and containvarious interfering organic compounds which must be removedby adsorption on macroreticular resin4prior to anal
16、ysis.5. Significance and Use5.1 This test method is useful for analysis of many naturalwaters that contain thiocyanate from organic decompositionproducts and waste water discharges. Some industrial wastes,such as those from the metallurgical processing of gold ores,steel industry, petroleum refining
17、, and coal gasification, maycontain significant concentrations of thiocyanate. Thiocyanateper se is not recognized as a toxic chemical compound.However, when chlorinated, thiocyanate is converted to thehighly toxic and volatile cyanogen chloride at high pH.Oxidation of thiocyanate may also release t
18、oxic hydrogencyanide. The user of the method is advised to perform holdingtime studies in accordance with Practice D4841 wheneveroxidants are present in the samples.5.1.1 For information on the impact of cyanogens andcyanide compounds, see Appendix X1 of Test Method D2036.6. Interferences6.1 Hexaval
19、ent chromium interference is removed by ad-justing the pH to 2 with concentrated nitric acid and addingferrous sulfate. Raising the pH to 8.5-9 with sodium hydroxideprecipitates Fe (III) and Cr (III) as the hydroxides, which areremoved by filtration.6.2 Reducing agents that reduce Fe (III) to Fe (II
20、), thuspreventing formation of the ferric thiocyanate complex, aredestroyed by a few drops of hydrogen peroxide.6.3 High concentrations of cyanide in proportion to theconcentration of thiocyanate will react with the iron to formcolored complexes.6.4 Colored or interfering organic compounds must bere
21、moved by adsorption on macroreticular adsorption resin priorto analysis.NOTE 1Examples of interfering compounds are fluoride, phosphate,oxalate, arsenate, tartrate, borate, etc. which form complexes with iron.5Production of a red color with ferric ions is typical of phenols, enols,oximes, and acetat
22、es.66.5 Oxidation of thiocyanate may also react to formcyanides, resulting in low results. The user of the method isadvised to perform holding time studies in accordance withPractice D4841 whenever oxidants are present in the samples.6.6 Removal of sulfides for cyanide analysis preservationmay resul
23、t in reaction of cyanide to form thiocyanate. Use aseparate sample for thiocyanate analysis than the one preservedfor cyanide analysis.7. Apparatus7.1 Spectrophotometer or Filter Photometer, suitable forabsorbance measurements at 460 nm and using a 5-cm cell.Filter photometers and photometric practi
24、ces used in this testmethod shall conform to Practice E60. Spectrophotometersshall conform to Practice E275.7.2 ColumnChromatographic, glass, 12-mm inside diam-eter by 600-mm length, equipped with a reservoir andstopcock, or a 50-mLburet with a glass wool plug and a funnelattached with a short piece
25、 of tubing.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 to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society.78.2 Purity of WaterUnl
26、ess otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D1193, Type I or II, and demonstrated to befree of specific interference for the test being performed.8.3 Acetone.8.4 Ferric Nitrate Solution (404 g/L)Dissolve 404 g offerric nitrate (Fe(
27、NO3)39H2O) in about 800 mLof water.Addto this solution 80 mL of concentrated nitric acid. Mix anddilute to 1 L with water.8.5 Hexane.8.6 Hydrogen Peroxide Solution(H2O2), 30 %.8.7 Macroreticular Resin,818- to 50-mesh or equivalent.8.8 Methyl Alcohol.8.9 Nitric AcidConcentrated HNO3, sp gr 1.42.8.10
28、Nitric Acid (0.1 M)Mix 6.4 mLof concentrated nitricacid in about 800 mL of water. Dilute to 1 L with water andmix.8.11 Thiocyanate Solution, Stock (1 mL = 1.0 mg SCN)Dissolve 1.673 g of potassium thiocyanate (KSCN) in waterand dilute to 1 L.8.12 Thiocyanate Solution, Standard (1 mL = 0.01 mgSCN1)Dil
29、ute 10 mL of the stock thiocyanate solution to 1L with water. Prepare fresh for each use. See 10.4.8.13 Sodium Hydroxide Solution (4 g/L)Dissolve4gofNaOH in about 800 mL of water. Mix and dilute to 1 L withwater.4Spencer, R. R., Leenheer, J., and Marti, V. C., “Automated ColorimetricDetermination of
30、 Thiocyanate, Thiosulfate, and Tetrathionate in Water, AOAC94th Annual Meeting, Washington, DC, 1980.5Newman, A. A. (ed.), Chemistry and Biochemistry of Thiocyanic Acid and ItsDerivatives, Academic Press, New York, NY, 1975.6Shriner, R. L., and Fuson, R. C., Identification of Organic Compounds, John
31、Wiley these should bedisposed of properly.10. Sampling10.1 Collect the sample in accordance with SpecificationD1192 and Practices D3370.10.2 Thiocyanate is stable in both the acid and alkaline pHrange.10.3 If the sample is to be preserved for cyanide, remove thesulfide before stabilization at a high
32、 pH in accordance withPractices D7365 as follows: Treat the sample immediatelyusing any or all of the following techniques as necessary,followed by adjustment of the sample to pH 1213 andrefrigeration.10.3.1 SulfideTest for the presence of sulfide by placing adrop of sample on a lead acetate test st
33、rip that has beenpreviously moistened with acetate buffer. If the test strip turnsblack, sulfide is present (above 50 mg/L S2-) and treatment isnecessary as described in Sections 10.3.1.1 or 10.3.1.2.Ifthetest is negative and there are no further interferences suspected,adjust the pH to 1213, refrig
34、erate, and ship or transport to thelaboratory.10.3.1.1 If the sample contains sulfide as indicated with alead acetate test strip or is known to contain sulfides that willinterfere with the test method, dilute the sample with reagentwater until the lead acetate test strip no longer indicates theprese
35、nce of sulfide (50 mg/L S2-) or until the interference isno longer significant to the analytical test method. Forexample, add 200 mL of freshly collected sample into a bottlecontaining 800 mL of reagent water, then test for sulfide againas indicated in 10.3.1. If the test for sulfide is negative, ad
36、justthe pH to 1213, refrigerate, and ship or transport to thelaboratory. If the test for sulfide is still positive, further dilutionis required; however, be careful not to over dilute the sample asthe detection limit will be elevated by this factor. In theaforementioned example, the dilution factor
37、would be equal to5 (total volume/sample volume). Clearly indicate the dilutionvolumes on the sample and chain-of-custody form so that thelaboratory can mathematically correct the result.10.3.1.2 Alternatively, sulfide can be removed by precipita-tion if free cyanide is the only form of cyanide to be
38、 measured(Test Method D7237). For removal of sulfide by precipitation,if the pH is less than pH 11, raise the pH to 11 with NaOHsolution, and then add approximately 1 mg of powderedcadmium chloride for each ml of sample. Cap and shake thecontainer to mix. Allow the precipitate to settle and test the
39、sample with lead acetate paper for residual sulfide. Ifnecessary, add more cadmium chloride but avoid addingexcess. Finally filter through a 0.45 m filter. Refrigerate, thentransport or ship the filtrate to the laboratory.NOTE 2Some analytical methods prescribe the use of lead carbonateor lead aceta
40、te to precipitate sulfide; however, sulfide and cyanide canform thiocyanate in the presence of lead causing decreased cyaniderecoveries; therefore, lead carbonate and lead acetate should be avoided.Methods that specify the addition of bismuth nitrate to treat sulfide duringtotal cyanide distillation
41、s have been demonstrated by ASTM committeeD19.06 to be ineffective. (WarningCyanide can be converted intothiocyanate in the presence of sulfide at a high pH, causing high results.)10.4 Thiocyanate is biodegradable. Samples that may con-tain bacteria should be preserved at pH 2 by the addition ofmine
42、ral acid and refrigerated.11. Preparation of Apparatus11.1 Resin ColumnMeasure out sufficient resin to fill thecolumn or columns into a beaker and add five times the resinvolume of acetone. Stir for 1 h with gentle agitation.11.2 Pour off the fines and the acetone from the settled resinand add five
43、times the resin volume of hexane. Stir for 1 h.11.3 Pour off any fines that may be present and the hexanefrom the settled resin and add five times the resin volume ofmethanol. Stir for 15 min.11.4 Pour off the methanol from the settled resin and addthree times the resin volume of NaOH solution (4 g/
44、L). Stir for15 min.11.5 Pour off the NaOH solution from the settled resin andadd three times the resin volume of 0.1 M HNO3. Stir for 15min.11.6 Pour off the HNO3solution from the settled resin andadd three times the resin volume of reagent water. Stir for 15min. Decant the water from the settled re
45、sin and use thispurified resin to fill the column.11.7 Attach the tip of the column to a source of reagentwater, and displace the air from the column with water to thebottom of the reservoir (tip of the funnel if a buret is used).11.8 Add the resin slurry to the reservoir (funnel) and allowit to fil
46、l the column by displacing the water to approximately400-mm depth. This procedure will give a uniform columnwith the correct degree of packing.11.9 When the resin has settled allow the water to drain tothe top of the resin bed. At no time should the liquid level bebelow the top of the resin bed.11.1
47、0 Add and drain five 5-mL increments of samplesolution to the column. Fill the reservoir (funnel) with theremaining (125 mL) solution and allow it to pass through thecolumn at a rate of 20 mL/min. Discard the first 50 mL ofeluate.11.11 Collect the next 50 mL of eluate in a clean, dry,graduated cylin
48、der. Use this portion for color development.11.12 Drain any remaining solution to the top of the resinbed. Regenerate the resin by the serial addition of five 5-mLand one 75-mL portions of NaOH solution (4 g/L), five 5-mLand one 25-mLportions of 0.1 M HNO3and five 5-mLand one75-mL portions of water.
49、 If the flow rate has reduced to 4 to 5mL/min, it is advisable to rinse the resin with 100 mL ofmethanol or backwash by introducing water into the bottom ofthe column and allowing it to escape at the top, or use bothD4193 08 (2013)13procedures. The rate of backwashing should be rapid enough toexpand the bed, but not allow loss of the resin.12. Calibration and Standardization12.1 Prepare a series of thiocyanate standards containing0.0 to 2.0 mg SCN/Lby pipetting 0-(blank) to 40-mLaliquotsof standard thiocyanate solution into 200-mLvolumetric flasks.D
