1、Designation: D 4954 89 (Reapproved 2003)Standard Test Method forDetermination of Nitrilotriacetates in Detergents1This standard is issued under the fixed designation D 4954; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the determination of nitrilo-triacetates (NTA) in detergents.1.2 This standard does not
3、 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 safetyprecautions, see 6.5.
4、2. Summary of Test Method2.1 A known excess amount of copper nitrate solution isadded to the detergent sample under controlled pH conditions.The uncomplexed copper is back-titrated potentiometricallywith a standard NTA solution using a copper ion specificelectrode. The millimoles of NTA in the sampl
5、e are equivalentto the millimoles of copper added, less the millimoles of theNTA titrant.3. Significance and Use3.1 This test method is suitable in research, development,and manufacturing control to monitor the level of NTA, asequestering agent, in powder and liquid detergents.3.2 Accurate determina
6、tion of a sequestering agent is im-portant in evaluating cost and performance of detergent prod-ucts.4. Interferences4.1 The presence of substances that will make coppercomplex like citrate, formate, ethylenediaminetetraacetate, andphosphonate, will interfere positively in the determination ofNTA.5.
7、 Apparatus5.1 Volumetric Flasks, 200-mL, 500-mL, 1000-mL.5.2 Beakers, 200-mL (tall form), 250-mL, 1000-mL.5.3 Pipets, 25-mL, 100-mL.5.4 Graduated Cylinders, 10-mL, 25-mL.5.5 Copper Ion Electrode (Orion Model 94-29).5.6 Single Junction Reference Electrode (Orion Model 90-01), filled with Orion 90-00-
8、01 solution.5.7 pH Combination Electrode.5.8 Burets, 10-mL, 25-mL, 50-mL.5.9 pH Meter, with millivolt capabilities.5.10 Automatic Titratormay be substituted for 5.8 and5.9.5.11 Magnetic Stirrer/Hot Plate.5.12 Balance, with 1-mg sensitivity.6. Reagents6.1 Purity of ReagentsReagent grade chemicals sha
9、ll beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to specifications of the Committeeon Analytical Reagents of the American Chemical Society,where such specifications are available.2Other grades may besubstituted, provided it is first ascertained that t
10、he reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Disodium Ethylenediaminetetraacetate (EDTA), 0.1 M.36.3 Nitric Acid, concentrated.6.4 Sodium Hydroxide, 50 % reagent solution.6.5 Sodium Hydroxide, 20 % solution. Mix 40 g of the 50 %sol
11、ution with 60 g of water. Cool. Wear a face shield duringmixing.6.6 Cupric Nitrate, 0.1 M. Weigh (to the nearest 0.1 g) 6.3g of copper metal and transfer into a 600-mL beaker. Add about100 mL of water. Place a magnetic bar into the beaker andplace on a stirrer/hotplate. Add 30 mL of concentrated nit
12、ricacid while stirring and heat gently. Stir until the copper metaldissolves. Add more nitric acid if undissolved metal remains.After dissolution, cool and transfer quantitatively to a 1-Lvolumetric flask. Dilute to the mark and mix the solution well.6.6.1 Alternatively, weigh out (to the nearest 1
13、g) 23 g ofreagent grade cupric nitrate, 212 hydrate crystals, and transferto a 600-mL beaker. Add 400 mL of water. Stir to dissolve thecrystals and add 5 mL of concentrated nitric acid. Transfer toa 1-L volumetric flask, dilute to the mark and mix well.6.7 Trisodium Nitrilotriacetate Monohydrate (NT
14、A), 0.3 M.Weigh out (to the nearest 1 g) 41 g of NTA and dissolve in 4001This test method is under the jurisdiction of ASTM Committee D12 on Soapsand Other Detergents and is the direct responsibility of Subcommittee D12.12 onAnalysis of Soaps and Synthetic Detergents.Current edition approved May 26,
15、 1989. Published July 1989.2American Chemical Society, 1155 16th St., NW, Washington, DC 20036.3EDTA solution is available from J. T. Baker Inc., already standardized againstNIST Reference Material Calcium Carbonate.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
16、, PA 19428-2959, United States.mL of water in a 600-mL beaker. Transfer to a 500-mLvolumetric flask, dilute to the mark and mix well.6.8 Sodium Acetate Buffer Solution, Dissolve 68 g of re-agent sodium acetate, trihydrate, in 500 mL of water in a 1-Lbeaker. Add 30 g of glacial acetic acid. Transfer
17、to a 1-Lvolumetric flask, dilute with water to the mark and mix well.The pH of this solution should be 4.6 to 4.8.7. Standardization of 0.1-M Cupric Nitrate7.1 Add 50 mL of water into a 200-mL tall form beaker. Add3 mL of concentrated nitric acid from a graduated cylinder.Transfer by pipet a 25-mL a
18、liquot of the cupric nitrate solutioninto the beaker.7.2 Place the pH combination electrode into the solution.Adjust the pH to 1.0 to 1.1 by dropwise addition of 50 %NaOH solution. About 2 mL may be required. Towards the end,use the 20 % NaOH solution.7.3 Add 25 mL of the sodium acetate buffer solut
19、ion from agraduated cylinder. Adjust the pH to 4.6 to 4.7 by dropwiseaddition of the 20 % NaOH solution. Cool to room temperaturein a cold water bath.7.4 Bring the solution to the titration assembly and immersethe copper and single junction electrodes. Stir the solution.With the meter set for mV rea
20、ding, begin titrating with the 0.1M standard EDTA using a 25 or 50-mL buret. The first 22 mLof titrant can be added rapidly.7.5 Add 0.5-mL increments and record the mV readingsafter each addition. It may take 1 to 2 min to obtain stablereadings at the endpoint region. Determine the endpoint inaccord
21、ance with Table 1.7.6 Calculate the molarity of the cupric nitrate solution asfollows:Molarity of Cupric Nitrate 5 M 3 V!/25 (1)where:M = molarity of EDTA, andV = mL of EDTA.8. Standardization of NTA Solution8.1 Proceed as for the standardization of the 0.1-M cupricnitrate; except in this case, the
22、titrant will be the NTA solutionrather than EDTA solution. Use a 10-mL buret for the NTAtitrant.8.2 The first 6 mL can be added rapidly, then continue with0.5-mL increment additions. Determine the endpoint in accor-dance with Table 1.8.3 Calculate the molarity of the NTA as follows:Molarity of NTA 5
23、 V13 M!/V2(2)where:V1= mL of cupric nitrate,M = molarity of cupric nitrate, andV2=mLofNTA.9. Procedure9.1 Weigh to the nearest milligram 10 g of detergent andslurry in water. Reduce the sample size accordingly if the NTAcontent is greater than 25 %. Transfer to a 500-mL volumetricflask, dilute to th
24、e mark, and stir to mix well.9.2 While stirring the sample, pipet out a 100-mL aliquotand transfer into a 250-mL tall form beaker.9.3 Add 3 mL of concentrated nitric acid from a 10-mLgraduated cylinder while stirring. Let the sample set for 5 min.Place the pH combination electrode in the sample, the
25、ncontinue adding the nitric acid while stirring until pH equals 0.9.4 Add 25 mL of the standard 0.1-M cupric nitrate solutionfrom a pipet into the sample while stirring.9.5 Adjust the pH to 1.0 to 1.1 by dropwise addition of the50 % or the 20 % NaOH solution as required.9.6 Add 25 mL of sodium aceta
26、te buffer solution using a25-mL graduated cylinder while stirring. Adjust pH to 4.6 to4.7 with 20 % NaOH solution.9.7 Rinse the electrodes with water into the sample beaker.Cool the sample to room temperature in a cold water bath.9.8 Place the copper electrode and single junction referenceelectrode
27、into the sample. Turn the meter to the mV mode.9.9 Titrate with the NTA solution using a 10-mL buret. Itmay take a few minutes at the start to attain a stable reading.Add the titrant in 0.5-mL increments and record the mVreading after each addition. Add at least two increments pastthe break point.9.
28、10 Determine the endpoint in accordance with Table 1.10. Calculation10.1 Calculate the percentage of Na3NTAH2O as follows:% weight of Na3NTAH2O (3)5 A 3 M1! 2 B 3 M2!# 3 0.275 3 100!/WTABLE 1 Determination of Inflection PointANOTE 1Volume of NTA required to react with 25 mL of cupric nitratesolution
29、 (0.0972 M).NTA, mL mV,(+)0 3031.00 3002.00 2973.00 2944.00 2915.00 2876.00 2837.00 275 DmV D(DmV)7.50 27010V18.00 260 36 D146V28.50 214 25 D2219.00 1939.50 18810.00 186AEnd Point = V1+ (V2V1) 3 (D1/(D1+D2).= 8.00 + (8.50 8.00) 3 (36/(36 + 25).= 8.00 + (0.5) 3 (0.59).= 8.00 + 0.30.= 8.30 mL.Then,Mol
30、arity of NTA 525.00 mL cupric nitrate 3 0.0972 M8.30 mL NTA5 0.2928 MD 4954 89 (2003)2where:A = mL of cupric nitrate added to the sample,M1= molarity of cupric nitrate,B = mL of NTA titrant,M2= molarity of NTA titrant, andW = weight of sample, in grams, present in aliquot.11. Precision and Bias11.1
31、Precision:11.1.1 In this study, two detergent samples with averageNTA contents, 14.93 and 10.02 weight %, were determined.Each sample was analyzed in duplicate, twice, by a givenanalyst. Each duplicate analysis was done on a different day.11.1.2 Repeatability (Single Analyst)The pooled standarddevia
32、tion of results (each the average of duplicates) for twosamples obtained by the same analyst on different days, hasbeen estimated to be 0.24 weight % at 12 df. Two suchaverages should be considered suspect (95 % confidence level)if they vary by more than 0.74 weight % absolute.11.1.3 Reproducibility
33、 (Multilaboratory)The pooled stan-dard deviation of results (each the average of duplicates) forthe two samples obtained by analysts in different laboratories,has been estimated to be 0.45 weight % at 10 df. Two suchaverages should be considered suspect (95 % confidence level)if they vary by more th
34、an 1.4 weight % absolute.11.1.4 Checking Limits for DuplicatesReport the NTAcontent of the sample to the nearest 0.1 weight %. Duplicateruns that agree within 0.7 weight % are acceptable foraveraging (95 % confidence level).11.2 BiasNo statement of bias can be made for this testmethod, since no acce
35、pted reference material to determine thebias is available.12. Keywords12.1 copper ion electrode; nitrilotriacetate; NTA; titrationASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard a
36、re expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not
37、 revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which y
38、ou may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 4954 89 (2003)3
