1、Designation: D 3372 02 (Reapproved 2007)e1Standard Test Method forMolybdenum in Water1This standard is issued under the fixed designation D 3372; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number i
2、n parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTESections 5.2 and 13.5 were updated editorially in September 2007.1.
3、 Scope1.1 This test method covers the determination of dissolvedand total recoverable molybdenum in most waters, wastewa-ters, and brines by atomic absorption spectroscopy.21.2 This test method is applicable in the range from 1 to 25g/L of molybdenum. The range may be extended by dilutionof the samp
4、le.1.3 This test method has been used successfully with naturaland reagent waters. It is the users responsibility to ensure thevalidity of this test method for waters of untested matrices.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
5、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 specificprecautionary statements, see Note 3 and Note 9.2. Referenced Documents2.1 ASTM Standards:3D 1129 Terminology Rela
6、ting to WaterD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 4691 Practice for Measuring Elements in Water by FlameAtomic Absorption Spectrophoto
7、metryD 4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD 5810 Guide for Spiking into Aqueous SamplesD 5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 Definitions: For defi
8、nitions of terms used in this testmethod, refer to Terminology D 1129.3.2 Definition of Term Specific to This Standard:3.2.1 laboratory control samplea solution with the certi-fied concentration(s) of the analytes.3.2.2 total recoverable molybdenuman arbitrary analyti-cal term relating to the forms
9、of molybdenum that aredeterminable by the digestion procedure described in this testmethod.4. Summary of Test Method4.1 Molybdenum is determined by atomic-absorption spec-trophotometry. The element is chelated with8-hydroxyquinoline, extracted with methyl isobutyl ketone,and the extract aspirated in
10、to the nitrous oxide-acetylene flameof the spectrophotometer.5. Significance and Use5.1 Molybdenum can be found in waste that results fromchemical cleaning of components in which the metal is alloyed.5.2 National Pollution Discharge Elimination System (NP-DES) permits or other standards, or both, re
11、quire monitoringpollutants in waste discharged onto the water shed of, or into,navigable waters, and those disposed of in such a manner thateventual contamination of underground water could result.5.3 This test method affords an accurate and sensitive meansof determining compliance with those permit
12、s.6. Interferences6.1 Vanadium (V) and iron (III) enhance the absorption,while chromium (VI) and tungsten (VI) suppress it. Theseinterferences are eliminated by the addition of ascorbic acid.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of
13、 Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Aug. 1, 2007. Published September 2007. Originallyapproved in 1975. Last previous edition approved in 2002 as D 3372 02.2Chau, Y. K., and Lum-Shue-Chan, K., “Atomic Absorption Determination ofMicrogram Quantities of Moly
14、bdenum in Lake Waters,” Analytica Chimica Acta,Vol 48, 1969, p. 205.3For 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 w
15、ebsite.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 Atomic-Absorption Spectrophotometer, for use at 313.3nm. A general guide for the use of flame atomic absorptionapplications is given in Practice D 4691.NOTE 1The
16、manufacturers instructions should be followed for allinstrumental parameters.7.1.1 Molybdenum Hollow-Cathode Lamp.7.2 Pressure-Reducing ValvesThe supplies of fuel andoxidant shall be maintained at a pressure somewhat higher thanthe controlled operating pressure of the instrument by suitablevalves.8.
17、 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 on Analytical Reagents of the American Chemical Society,where such specifications are avai
18、lable.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingt
19、o Specification D 1193, Type I, II, or III water. Type I ispreferred and more commonly used. Type II water wasspecified at the time of round robin testing of these testmethods.NOTE 2The user must ensure the type of reagent water chosen issufficiently free of interferences. The water should be analyz
20、ed using thetest method.8.3 Ascorbic Acid Solution (10 g/L)Dissolve1gofascorbic acid in water and dilute to 100 mL.8.4 Bromphenol Blue Indicator Solution (1 g/L)Dissolve0.1 g of bromphenol blue in 100 mL of 50 % ethanol orisopropanol.8.5 Hydrochloric Acid (1 + 49)Mix 20.0 mL of concen-trated hydroch
21、loric acid (HCl, sp gr 1.19) with water and diluteto1L.8.6 8-Hydroxyquinoline-Methyl Isobutyl Ketone Solution(10 g/L)Dissolve1gof8-hydroxyquinoline in 100 mL ofmethyl isobutyl ketone. Prepare fresh daily.8.7 Methyl Isobutyl Ketone (MIBK).8.8 Molybdenum Solution, Stock (1.0 mL = 100 g Mo)Dissolve 0.1
22、500 g of molybdenum trioxide (MoO3)in10mLof water containing 1 mL of NaOH (100 g/L) (warm ifnecessary). Make just acid with HCl (1 + 49) and dilute to1000 mL with water.58.9 Molybdenum Solution, Intermediate (1.0 mL = 1.0 gMo)Dilute 10.0 mL of molybdenum stock solution to 1000mL with water.8.10 Moly
23、bdenum Solution, Standard (1.0 mL = 0.1 gMo)Immediately before use, dilute 10.0 mL of intermediatemolybdenum solution of 100 mL with water. This standard isused to prepare working standards at the time of analysis.8.11 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).8.12 Sodium Hydroxide Solu
24、tion (100 g/L)Dissolve 100 gof sodium hydroxide (NaOH) in water and dilute to 1 L.8.13 MIBK-Saturated WaterThoroughly mix equal vol-umes of MIBK and water in a separatory funnel. Allow layersto separate. Collect and store water and MIBK, respectively, inproperly marked containers.8.14 Water-Saturate
25、d MIBKUse MIBK prepared from8.13.8.15 Nitrous OxideCommercially available nitrous oxideis suitable as oxidant.8.16 Acetylene FuelStandard, commercially availableacetylene is the usual fuel. Acetone, always present in acety-lene cylinders, will affect analytical results. Generally, replac-ing the ace
26、tylene cylinder with 50 psig (345 kPa) remainingprevents acetone interference; however it has been reportedthat cylinders with pressure at 100 psig (670 kPa) or greaterwill cause interference.NOTE 3Warning: “Purified” grade acetylene contains a specialproprietary solvent rather than acetone and shou
27、ld not be used. It canweaken the walls of poly(vinyl chloride) tubing that carries the acetyleneto the burner, causing a potentially hazardous situation.9. Sampling9.1 Collect the sample in accordance with Practices D 3370.The holding time for the samples may be calculated inaccordance with Practice
28、 D 4841.9.2 To preserve the samples add concentrated HNO3(sp gr1.42) to a pH of 2 or less immediately at the time of collection;normally about 2 mL/L is required. If only dissolved molyb-denum is to be determined, filter the samples at time ofcollection through a 0.45-m membrane filter before acidif
29、ica-tion.10. Standardization10.1 Prepare in 200-mL volumetric flasks a blank andsufficient standards containing from 0.0 to 2.5 g of molybde-num by diluting 0.0 to 25.0-mL portions of the standardmolybdenum solution to 100 mL with water.10.2 Proceed as directed in 11.5 to 11.11.10.3 Construct an ana
30、lytical curve by plotting the absor-bances of standards versus micrograms of molybdenum.NOTE 4The burner must be conditioned just prior to standardizationand running of sample extracts by aspirating water-saturated MIBK untilthe flame stabilizes. Some systems have required as long as 10 min forcondi
31、tioning.11. Procedure11.1 For total recoverable molybdenum, add 5 mL ofconcentrated nitric acid to 100 mL of the sample in a 250-mLErlenmeyer flask and mix well. Heat the sample, withoutboiling, on a steam bath or hot plate in a well-ventilated fumehood until the volume has been reduced to 15 to 20
32、mL.NOTE 5When treating samples of brine or a sample containing a large4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChem
33、icals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5Commercial Stock Standards may also be purchased.D 3372 02 (2007)e12amount of solids, the amount of reduction in volume is left to thediscretion o
34、f the analyst.11.2 If color in the digested solution indicates the presenceof partially oxidized materials, add additional acid and ap-proximately 90 mL of reagent water to the cooled solution andrepeat the digestion.11.3 Cool and filter the digested solution through a suitablefilter (such as a fine
35、-textured, acid-washed, ashless paper) intoa 100-mL volumetric flask. Wash and filter paper two to threetimes with reagent water, collecting washings in flask; make upto volume with reagent water.NOTE 6If only dissolved molybdenum is to be determined, filterportion of the sample through a 0.45-m mem
36、brane filter and proceed with11.4.11.4 Pipette a volume of sample containing less than 2.5 gof molybdenum (100 mL maximum) into a 200-mL volumetricflask and adjust the volume to 100 mL with water.11.5 Add 5 mL of ascorbic acid solution and mix.11.6 Add 2 drops of bromphenol blue indicator solution a
37、ndmix.11.7 Adjust the pH by addition of NaOH solution (100 g/L)until a blue color persists. Add HCl (1 + 49) by drops until theblue color just disappears in both the standards and the sample;then add 2.5 mL of HCl (1 + 49) in excess. The pH at this pointshould be 2.3.NOTE 7The pH adjustment in 11.7
38、may be made with the use of a pHmeter instead of using an indicator.11.8 Add 5.0 mLof 8-hydroxyquinoline-MIBK solution andshake vigorously for 15 min.11.9 Allow the layers to separate; then carefully add watersaturated with MIBK so as not to disturb the ketone layer untilit is completely in the neck
39、 of the flask.NOTE 8The ketone layer should be centrifuged to remove all traces ofwater if the extract is to be stored for several hours before analysis.11.10 Zero the instrument while aspirating the water-saturated MIBK.11.11 Aspirate the ketone layer of standards and samplesinto the nitrous oxide-
40、acetylene flame of the spectrophotometerand record the scale reading for each standard and sampleagainst the blank.NOTE 9Warning: Aspirating methyl isobutyl ketone into a nitrousoxide-acetylene flame can be dangerous. To minimize the chances of anaccident, scrupulously follow recommended practices f
41、or using such asystem.12. Calculation12.1 Determine the weight of molybdenum in each sampleby referring to the analytical curve. Calculate the concentrationof molybdenum in micrograms per liter as follows:Molybdenum, g/L 5 1000/A! 3 Bwhere:A = volume of sample, mL, andB = weight of molybdenum in sam
42、ple, g.13. Precision and Bias613.1 The single-operator and overall precision of this testmethod within its designated range based on data from fourlaboratories, which includes a total of five operators analyzingeach sample on three different days, may be expressed asfollows:ST5 0.072X 1 0.450SO5 0.0
43、39X 1 0.610where:ST= overall precision, g/L,SO= pooled single-operator precision, g/L, andX = concentration of molybdenum, g/L.13.2 Recoveries of known amounts of molybdenum (fromMoO3) added to a series of natural waters for the samelaboratories and operators were as follows:AmountAdded,g/LAmountFou
44、nd,g/LBias % BiasStatistically Sig-nificant (95 %ConfidenceLevel)3.0 3.07 0.07 2.3 no9.5 9.38 0.12 1.3 no18.0 16.86 1.14 6.3 yes13.3 This test method was evaluated with reagent andnatural water matrices. These data may not apply to waters ofother matrices.13.4 Practice D 2777 requires a minimum of s
45、ix indepen-dent laboratories and analysts, respectively, for a collaborativestudy of a test method. Since the numbers listed for this studydo not meet these requirements, that deficiency is recordedhere for the benefit of the user of this test method.NOTE 10The nitric acid digestion steps were not p
46、erformed in theround robin of this test method. It is an approved and recommendedpractice for determining total recoverable metals by atomic absorptionspectrometry; however, its use can be expected to increase the variabilityof the final results. The user should verify its suitability for a matrix o
47、finterest by evaluating recovery for spikes that have been taken through thedigestion process. (Guide D 5810)13.5 Precision and bias for this test method conforms toPractice D 2777 77, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofD 2777 06, these precisi
48、on 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 molybdenum in water.14.2 The instrument shall be calibrated using a minimum offour ca
49、libration standards and a calibration blank. The calibra-tion correlation coefficient shall be equal to or greater than0.990. In addition to the initial calibration blank, a calibrationblank shall be analyzed at the end of the batch run to ensurecontamination was not a problem during the batch analysis.14.3 An instrument check standard shall be analyzed at aminimum frequency of 10 % throughout the batch analysis.6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:
