DIN 38413-8-2000 en 3132 German standard methods for the examination of water waste water and sludge - Single components (group P) - Part 8 Determination of nitrilotriacetic acid (.pdf

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1、ICS 13.060.50Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung Einzelkomponenten(Gruppe P) Teil 8: Bestimmung der gelsten Komplexbildner Nitrilotriessigsure (NTA), Ethylen-dinitrilotetraessigsure (EDTA) und Diethylentrinitrilopentaessigsure (DTPA) mit der Flssig-chromatograph

2、ie (LC) (P 8)In keeping with current practice in standards published by the International Organization for Standardization(ISO), a comma has been used throughout as the decimal marker.ForewordThis standard has been jointly prepared by the Normenausschuss Wasserwesen (Water Practice StandardsCommitte

3、e) and Study Group Wasserchemie (Water Chemistry) of the Gesellschaft Deutscher Chemiker(German Chemists Society) (see Explanatory notes).Expert assistance and specialized laboratories will be required to perform the analyses specified in thisstandard. Existing safety instructions shall be observed.

4、Depending on the objective of the analysis, a check shall be made on a case-by-case basis as to whetherand to what extent additional conditions will have to be specified.IntroductionGiven the variety of equipment components, the corresponding scope for variety within the proceduralframework, both eq

5、uipment and method stages, can only be described in generalized form.1 ScopeThe method specified in this standard serves to determine the concentration of nitrilotriacetic acid (NTA),ethylenediamine tetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA) or their salts in waterand was

6、te water.The method is suitable for the concentration ranges specified in table 1; its scope may be extended to coverhigher concentrations by dilution of the sample.Table 1: Concentration rangesSubstanceConcentration range,in mg/l1)NTA 0,1 up to 20EDTA 0,1 up to 20DTPA 0,2 up to 201) Sample to be di

7、luted if necessary.Ref. No. DIN 38413-8 : 2000-09English price group 08 Sales No. 010804.02DEUTSCHE NORM September 200038413-8Continued on pages 2 to 10. No part of this translation may be reproduced without the prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 1

8、0772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).German standard methods for the examination of water, waste water and sludgeIndividual constituents (group P)Part 8: Determination of nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethyl

9、enetriamine pentaacetic acid (DTPA)by liquid chromatography (P 8)Translation by DIN-Sprachendienst.In case of doubt, the German-language original should be consulted as the authoritative text.Page 2DIN 38413 : 2000-092 Normative referencesThis standard incorporates, by dated or undated reference, pr

10、ovisions from other publications. These normativereferences are cited at the appropriate places in the text, and the titles of the publications are listed below. Fordated references, subsequent amendments to or revisions of any of these publications apply to this standardonly when incorporated in it

11、 by amendment or revision. For undated references, the latest edition of thepublication referred to applies.DIN 12491 Vacuum desiccators for laboratory useDIN 12697 Class AS fast delivery graduated pipettes with a waiting time of 15 seconds, for laboratory useDIN 32633 Standard addition methods used

12、 in chemical analysisDIN 32645 Establishing the decision limit, detection limit and determination limit under repeatabilityconditions in chemical analysis Terminology, methods and evaluationDIN 38402-11 German standard methods for the examination of water, waste water and sludge Generalinformation (

13、group A) Sampling of waste water (A 11)DIN 38402-41 German standard methods for the examination of water, waste water and sludge Generalinformation (group A) Interlaboratory tests, planning and organization (A 41)DIN 38402-42 German standard methods for the examination of water, waste water and slud

14、ge Generalinformation (group A) Evaluation of interlaboratory tests (A 42)DIN 38402-51 German standard methods for the examination of water, waste water and sludge Generalinformation (group A) Calibration of analytical methods, evaluation of analytical resultsand linear calibration functions used to

15、 determine the performance characteristics ofanalytical methods (A 51)DIN EN ISO 1042 Laboratory glassware One-mark volumetric flasks (ISO 1042 : 1998)ISO 8466-2 : 2001 Water quality Calibration and evaluation of analytical methods and estimation ofperformance characteristics Part 2: Calibration str

16、ategy for non-linear second ordercalibration functions3 PrincipleNTA, EDTA and DTPA are complexed using iron(III) ions and then separated by liquid chromatography. Areversed-phase material is used as stationary phase for ion pair chromatography, the mobile phase being nitricacid, tetrabutylammonium

17、hydrogensulfate or tetrabutylammonium hydroxide solutions. Detection is carried outby direct measurement of the UV absorption. The concentrations of the complexing agents are determined bycalibrating the overall procedure.4 InterferenceHigh concentrations of inorganic ions (e.g. phosphate, chloride,

18、 nitrate, sulfate) may lead to results that are toolow due to cross-sensitivities. The determination of DTPA is least affected by salts, while that of NTA is mostaffected, phosphate and chloride having a stronger effect than sulfate and nitrate.Although some organic compounds (e.g. aminopolycarboxyl

19、ic acids, phosphonic acids) may interfere, organicsubstances do not generally interfere since measurement is made at wavelengths of 260 nm and above.The wide peak at the beginning of chromatograms obtained with reversed-phase columns (see figure 2) due tothe unreacted excess of iron(III) ions can by

20、 avoided by using a suitable suppressor system (e.g. a cationexchanger) prior to UV detection.When checking the method under the conditions given in subclause 6.2, using the concentrations specified intable 2, there was no interference for sample volumes of up to 50 ml.Table 2: Cross-sensitivities o

21、f complexing agentsComplexing agent Concentration of ions checked1 mg/l NTA + 10000 mg/l sulfate+ 10000 mg/l nitrate+ 1000 mg/l chloride+ 100 mg/l phosphate1 mg/l EDTA + 10000 mg/l sulfate+ 5000 mg/l nitrate+ 5000 mg/l chloride+ 1000 mg/l phosphate1 mg/l DTPA + 10000 mg/l sulfate+ 10000 mg/l nitrate

22、+ 10000 mg/l chloride+ 10000 mg/l phosphatePage 3DIN 38413 : 2000-09Metal ions other than iron that form complexes with NTA, EDTA or DTPA are likely to cause interference onlyat high concentrations since the iron(III) complexes have been found to be highly stable constants.Concentrations of copper(I

23、I) ions of up to 300 mg/l have no effect on the analytical result.If peaks of unknown origin occur (e.g. in waste water samples) or signals are superposed, the standard additionmethod specified in DIN 32633 shall be used to check the signals.5 Designation of methodDesignation of the method of determ

24、ining NTA, EDTA and DTPA by liquid chromatography (P 8):Method DIN 38413 P 86 ApparatusThe following equipment shall be used.6.1 High performance liquid chromatograph, with UV detector for reversed-phase chromatography (cf.figure 1).Figure 1: Liquid chromatograph system (schematic)6.2 Separating col

25、umnReversed-phase materials are to be used for separation, with tetrabutylammonium salts added to the eluent. Theefficiency of the column is influenced by various factors, such as column material and eluents. Only thosereversed-phase materials are suitable that contain no free silanol groups (end-ca

26、pped materials) and thatpermit separation of all the components along the base line after a complexing agent standard solution (e.g. anNTA, ETDA and DTPA standard mixture with a concentration of 1 mg/l) has been injected (cf. figure 2).In the case of chromatograms of test and standard solutions havi

27、ng high complexing agent concentrations, theresolution, R, with respect to the nearest (interfering) peak must not be less than 1,3 (see Appendix A forexamples of determining resolution).Figure 2: Example of a chromatogram as specified in this standard (UV detection at a wavelength of260 nm, end-cap

28、ped RP C18 phase material, eluent as in subclause 7.11)6.3 Other equipmentThe following additional equipment shall be used.6.3.1 Desiccator (e.g. as in DIN 12491).6.3.2 Volumetric flasks, of nominal capacities 100 ml and 1000 ml (e.g. DIN EN ISO 1042 A100 Cvolumetric flasks).Sample injectorEluent Pu

29、mp Precolumn SeparatingDetector Collection vesselcolumnRecording orevaluating unitElapsed time, in minPage 4DIN 38413 : 2000-096.3.3 Graduated pipettes, of nominal capacities 1 ml to 20 ml (e.g. DIN 12697 MPAS 1 001 pipettes) ormicrolitre pipettes.6.3.4 Membrane filter, of pore size 0,45 mm.6.3.5 Th

30、ermostating device (e.g. metal block), capable of being heated to (60 t 10) C with openings toaccommodate the test vessels (e.g. sealable test vessels, heat-resistant up to 100 C, of nominal capacity about1,5 ml, having a flanged rim and a closure cap with PTFE-coated inserts).7 Reagents7.1 GeneralO

31、nly analytical grade reagents shall be used and the water used shall have an electrical conductivity of less than1 mS/cm and not contain any particles larger than 0,45 mm.The following reagents shall be used.7.2 Nitric acid, HNO3, (r = 1,4 g/ml).7.3 Tetrabutylammonium hydrogensulfate, C16H37NO4S.7.4

32、 40 % (m/m) aqueous solution of tetrabutylammonium hydroxide, C16H37NO.7.5 Methanol, CH3OH.7.6 Iron(III) nitrate nonahydrate, Fe(NO3)3. 9H2O.7.7 Nitrilotriacetic acid (NTA), C6H9NO6.7.8 Ethylenediamine traacetic acid (EDTA), C10H16N2O8.7.9 Diethylenetriamine pentaacetic acid (DTPA), C14H23N3O10.7.10

33、 1,0 moc108/c108 sodium hydroxide solution, NaOH.7.11 Eluent, prepared, for example, by weighing 2,5 g of tetrabutylammonium hydrogensulfate and pipetting1,7 ml of tetrabutylammonium hydroxide into a 1000 ml volumetric flask, then adding 0,04 ml of nitric acid andmaking up to the mark with degassed

34、water. During use, ensure that the water does not absorb air again bykeeping it under a helium atmosphere and renewing it every two to three days.The solution thus obtained contains 0,6 mmol/l nitric acid, 7,4 mmol/l tetrabutylammonium hydrogensulfateand 2,6 mmol/l tetrabutylammonium hydroxide.7.12

35、Derivatization solution, prepared by weighing 1,5 g of iron(III) nitrate nonahydrate and 4,4 g oftetrabutylammonium hydrogensulfate into a 100 ml volumetric flask and making up to the mark with water.This solution contains 37 mmol/l iron(III) ions and 130 mmol/l tetrabutylammonium hydrogensulfate an

36、d will bestable for several weeks without refrigeration.7.13 Complexing agent stock solutions, containing 1000 mg/l of NTA, EDTA and DTPA, respectively, andprepared by introducing about 800 ml of degassed, low-oxygen water into each of three 1000 ml volumetricflasks, then dissolving 1 g of NTA, EDTA

37、 and DTPA in separate 10 ml portions of sodium hydroxide solution,transferring these solutions separately to the volumetric flasks prepared and making up to the mark with water.Alternatively, commercially available solutions having appropriate concentrations may be used.Instead of the free acids, th

38、e corresponding sodium salts may be used if commercially available, the initialmasses being determined from table B.1. In this case, sodium hydroxide solution need not be added.The solutions will be stable in polyethene or glass vessels at 2 C to 6 C for up to three months.7.14 Standard complexing a

39、gent solutions, prepared to suit requirements from the stock solutions andhaving various compositions and concentrations. As an example, standard solutions containing 10 mg/l NTA,EDTA and DTPA, respectively, may be prepared by pipetting 1 ml of complexing agent stock solution into eachof three separ

40、ate 100 ml volumetric flasks and making up to the mark with water. Further standard solutions canbe prepared similarly by diluting the complexing agent stock solution specified in subclause 7.13.Always use freshly prepared solutions.Store the standard solutions in glass or polyethylene vessels, but

41、always use the same vessels for the sameconcentration ranges to avoid entrainment effects.7.15 Complexing agent reference solutionsTo suit the expected complexing agent concentration, prepare at least five reference solutions covering theexpected concentration range as uniformly as possible from the

42、 stock or standard solution.For example, to cover the range of 0,2 mg/l to 2 mg/l of NTA, EDTA and DTPA, respectively, pipette 2 ml, 5 ml,Page 5DIN 38413 : 2000-0910 ml, 15 ml and 20 ml into a series of 100 ml volumetric flasks and make up to the mark with water. Theconcentrations of NTA, EDTA and D

43、TPA in these reference solutions will be 0,2 mg/l, 0,5 mg/l, 1 mg/l, 1,5 mg/land 2 mg/l, respectively.Prepare fresh reference solutions on every analysis day.7.16 Blank solutionUse water as the blank solution.8 Sampling and sample preparationCollect the samples as specified in DIN 38402-11 using cle

44、an glass or polyethylene containers.NOTE 1: In tests, samples acidified with sulfuric acid to a pH value of 2 remained stable for up to seven dayswhen stored in the dark at 2 C to 6 C.To every 20 parts of sample, add one part of derivatization solution, seal the sample vessel and heat for(20 t 5) mi

45、nutes at (60 t 10) C using, for example, a metal heating block. If it is not possible to analyse thesamples immediately after complexing, refrigerate them in the dark until used for the analysis.Use carefully selected rinsing agents, possibly water and nitric acid, to ensure that the equipment used

46、does notgive a blank reading.NOTE 2: When waste water samples are heated with iron(III) nitrate solution, a precipitate may form, but thisdoes not interfere with the analysis.Pretreat reference and blank solutions in the same way as test solutions.9 Procedure9.1 GeneralUse the chromatograph as speci

47、fied by the manufacturer. It will be ready for use once the base line is stable.Perform the calibration as specified in subclause 9.2 and analyse the samples and blank solutions as specifiedin subclause 9.3.9.2 CalibrationInject the standard solutions after pretreating them as described in clause 8

48、and cooling them to ambienttemperature. Compare the retention times of the individual complexing agents with those of the referencesolutions, bearing in mind that the retention times may depend on concentration and sample matrix. The peakheight or area is proportional to the concentration of the com

49、plexing agent concerned.Establish a calibration function as specified in DIN 38402-51 or ISO 8466-2 by chromatographing referencesolutions pretreated as described in clause 8. The peak height or area is proportional to the concentration of thecomplexing agent concerned.Determine the calibration function for the series of results thus obtained as specified in DIN 38402-51 orISO 8466-2.9.3 Sample analysisAfter establishing the calibration function as in subclause 9.2, inject the sample after pretreating it as in