1、Designation: D3372 12D3372 17Standard Test Method forMolybdenum in Water1This standard is issued under the fixed designation D3372; 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
2、indicates 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 test method covers the determination of dissolved and total recov
3、erable molybdenum in most waters, wastewaters, andbrines by atomic absorption spectroscopy.21.2 This test method is applicable in the range from 1 to 25 g/L of molybdenum. The range may be extended by dilution ofthe sample.1.3 This test method has been used successfully with natural and reagent wate
4、rs. It is the users responsibility to ensure thevalidity of this test method for waters of untested matrices.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values statedgivenin each system are mathematical conversions and may not be exact
5、equivalents; therefore, each system shall be used independentlyof the other.parentheses are mathematical conversion to inch-pound units that are provided for information only and are notconsidered standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated w
6、ith its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. For specific precautionary statements, see Note 38.16 and Note 1111.12.1.6 This international standard was dev
7、eloped in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Docum
8、ents2.1 ASTM Standards:3D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD1976 Test Method for Elements in Water by Inductively-Coupled Argon Plasma Atomic Emission SpectroscopyD2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 o
9、n WaterD3370 Practices for Sampling Water from Closed ConduitsD4691 Practice for Measuring Elements in Water by Flame Atomic Absorption SpectrophotometryD4841 Practice for Estimation of Holding Time for Water Samples Containing Organic and Inorganic ConstituentsD5673 Test Method for Elements in Wate
10、r by Inductively Coupled PlasmaMass SpectrometryD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis3. Terminology3.1 Definitions: For definitions of terms used in this test method, refer to Terminology D11
11、29.3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.1 This test method is under the jurisdiction ofASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.Current edition approved Sept. 1, 2012June 1, 2017
12、. Published October 2012June 2017. Originally approved in 1975. Last previous edition approved in 20022012 asD3372 02 (2007)D33721. 12. DOI: 10.1520/D3372-12.10.1520/D3372-17.2 Chau, Y. K., and Lum-Shue-Chan, K., “Atomic Absorption Determination of Microgram Quantities of Molybdenum in Lake Waters,”
13、 Analytica Chimica Acta, Vol 48,1969, p. 205.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is
14、 not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropr
15、iate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
16、13.2 Definitions of Terms Specific to This Standard:3.2.1 continuing calibration blank, na solution containing no analytes (of interest) which is used to verify blank response andfreedom from carryover.3.2.2 continuing calibration verification, na solution (or set of solutions) of known concentratio
17、n used to verify freedom fromexcessive instrumental drift; the concentration is to cover the range of calibration curve.3.2.3 laboratory control samplesample, na solution with the certified concentration(s) of the analytes.3.2.4 total recoverable molybdenummolybdenum, nan arbitrary analytical a desc
18、riptive term relating to the metal forms ofmolybdenum that are determinable by the digestion procedure describedrecovered in the acid-digestion procedure specified in thistest method.standard.4. Summary of Test Method4.1 Molybdenum is determined by atomic-absorption spectrophotometry. The element is
19、 chelated with 8-hydroxyquinoline,extracted with methyl isobutyl ketone, and the extract aspirated into the nitrous oxide-acetylene flame of the spectrophotometer.5. Significance and Use5.1 Molybdenum can be found in waste that results from chemical cleaning of components in which the metal is alloy
20、ed.5.2 National Pollution Discharge Elimination System (NPDES) permits or other standards, or both, require 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.
21、5.3 This test method affords an accurate and sensitive means of determining compliance with those permits.5.4 ICP-MS or ICP-AES may also be appropriate but at a higher instrument cost. See Test Methods D5673 and D1976.6. Interferences6.1 Vanadium (V) and iron (III) enhance the absorption, while chro
22、mium (VI) and tungsten (VI) suppress it. These interferencesare eliminated by the addition of ascorbic acid.7. Apparatus7.1 Atomic-Absorption Spectrophotometer, for use at 313.3 nm. A general guide for the use of flame atomic absorptionapplications is given in Practice D4691.NOTE 1The manufacturers
23、instructions should be followed for all instrumental parameters.7.1.1 Molybdenum Hollow-Cathode Lamp.7.2 Pressure-Reducing ValvesThe supplies of fuel and oxidant shall be maintained at a pressure somewhat higher than thecontrolled operating pressure of the instrument by suitable valves.8. Reagents a
24、nd Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are available.4 Oth
25、er grades may be used, provided it is first ascertained that the reagent is of sufficiently highpurity to permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean reagent water conforming toSpeci
26、fication D1193, Type I, II, or III water. Type I is preferred and more commonly used. Type II water was specified at the timeof round robin testing of these test methods.NOTE 2The user must ensure the type of reagent water chosen is sufficiently free of interferences.The water should be analyzed usi
27、ng the test method.8.3 Ascorbic Acid Solution (10 g/L)Dissolve 1 g of ascorbic acid in water and dilute to 100 mL.8.4 Bromphenol Blue Indicator Solution (1 g/L)Dissolve 0.1 g of bromphenol blue in 100 mLof 50 % ethanol or isopropanol.8.5 Hydrochloric Acid (1 + 49)Mix 20.0 mL of concentrated hydrochl
28、oric acid (HCl, sp gr 1.19) with water and dilute to 1L.8.6 8-Hydroxyquinoline-Methyl Isobutyl Ketone Solution (10 g/L)Dissolve 1 g of 8-hydroxyquinoline in 100 mL of methylisobutyl ketone. Prepare fresh daily.4 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society,
29、Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D33
30、72 1728.7 Methyl Isobutyl Ketone (MIBK).8.8 Molybdenum Solution, Stock (1.0 mL = 100 g Mo)Dissolve 0.1500 g of molybdenum trioxide (MoO3) in 10 mLof watercontaining 1 mL of NaOH (100 g/L) (warm if necessary). Make just acid with HCl (1 + 49) and dilute to 1000 mL with water. Apurchased molybdenum st
31、ock solution of appropriate known purity is also acceptable.8.9 Molybdenum Solution, Intermediate (1.0 mL = 1.0 g Mo)Dilute 10.0 mLof molybdenum stock solution to 1000 mLwithwater.8.10 Molybdenum Solution, Standard (1.0 mL = 0.1 g Mo)Immediately before use, dilute 10.0 mL of intermediatemolybdenum s
32、olution of 100 mL with water. This standard is used 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 Solution (100 g/L)Dissolve 100 g of sodium hydroxide (NaOH) in water and dilute to 1 L.8.13 MIBK-Saturated Water
33、Thoroughly mix equal volumes of MIBK and water in a separatory funnel. Allow layers toseparate. Collect and store water and MIBK, respectively, in properly marked containers.8.14 Water-Saturated MIBKUse MIBK prepared from 8.13.8.15 Nitrous OxideCommercially available nitrous oxide is suitable as oxi
34、dant.8.16 Acetylene FuelStandard, commercially available acetylene is the usual fuel. Acetone, always present in acetylenecylinders, will affect analytical results. Generally, replacing the acetylene cylinder with 345 kPa (50 psi) remaining preventsacetone interference; however it has been reported
35、that cylinders with pressure at 670 kPa (100 psi) or greater will causeinterference. (Warning“Purified” grade acetylene contains a special proprietary solvent rather than acetone and should not beused. It can weaken the walls of poly(vinyl chloride) tubing that carries the acetylene to the burner, c
36、ausing a potentially hazardoussituation.)NOTE 3Warning: “Purified” grade acetylene contains a special proprietary solvent rather than acetone and should not be used. It can weaken thewalls of poly(vinyl chloride) tubing that carries the acetylene to the burner, causing a potentially hazardous situat
37、ion.8.17 Filter PaperPurchase suitable filter paper. Typically the filter papers have a pore size of 0.45-m membrane. Materialsuch as fine-textured, acid-washed, ashless paper, or glass fiber paper are acceptable. The user must first ascertain that the filterpaper is of sufficient purity to use with
38、out adversely affecting the bias and precision of this test method.9. Sampling9.1 Collect the sample in accordance with Practices D3370. The holding time for the samples may be calculated in accordancewith Practice D4841.9.2 To preserve the samples add concentrated HNO3 (sp gr 1.42) to a pH of 2 or
39、less immediately at the time of collection;normally about 2 mL/L is required. If only dissolved molybdenum is to be determined, filter the samples at time of collectionthrough a 0.45-m membrane filter before acidification.NOTE 3Alternatively, the pH may be adjusted in the laboratory if the sample is
40、 returned within 14 days. within 14 days of collection. However, acidmust be added at least 24 hours before analysis to dissolve any metals that adsorb to the container walls. This could reduce hazards of working with acidsin the field when appropriate.10. Standardization10.1 Prepare in 200-mL volum
41、etric flasks a blank and sufficient standards containing from 0.0 to 2.5 g of molybdenum bydiluting 0.0 to 25.0-mL portions of the standard molybdenum solution to 100 mL with water.10.2 Proceed as directed in 11.511.6 to 11.1111.12.10.3 Construct Read directly in concentration if this capability is
42、provided with the instrument or plot construct an analyticalcurve by plotting the absorbances of standards versus micrograms of molybdenum.NOTE 4The burner must be conditioned just prior to standardization and running of sample extracts by aspirating water-saturated MIBK until theflame stabilizes. S
43、ome systems have required as long as 10 min for conditioning.11. Procedure11.1 An effective way to clean all glassware to be used for preparation of standard solutions or in the digestion step, or both,is by soaking the glassware for 2 h first with HNO3 (1 + 1) and then rinsing with reagent.11.2 For
44、 total recoverable molybdenum, add 5 mL of concentrated nitric acid to 100 mL of the sample in a 250-mL Erlenmeyerflask and mix well. Heat the sample, without boiling, sample (between 65C and 95C) on a steam bath or hot plate below boilingin a well-ventilated fume hood until the volume has been redu
45、ced to 15 to 20 mL.NOTE 5When treating samples of brine or a sample containing a large amount of solids, the amount of reduction in volume is left to the discretionof the analyst.D3372 173NOTE 6Many laboratories have found block digestion systems a useful way to digest samples for trace metals analy
46、sis. Systems typically consist ofeither a metal or graphite block with wells to hold digestion tubes. The block temperature controller must be able to maintain uniformity of temperatureacross all positions of the block. The digestion block must be capable of maintaining a temperature between 65C and
47、 95C. For trace metals analysis,the digestion tubes should be constructed of polypropylene and have a volume accuracy of at least 0.5%. 0.5 %. All lots of tubes should come with acertificate of analysis to demonstrate suitability for their intended purpose.11.3 If color in the digested solution indi
48、cates the presence of partially oxidized materials, add additional acid andapproximately 90 mL of reagent water to the cooled solution and repeat the digestion.11.4 Cool and filter the digested solution through a suitable filter (8.17) (such as a fine-textured, acid-washed, ashless paper)into a 100-
49、mL volumetric flask. Wash andthe filter paper two to three times with reagent water, collecting washings in flask; makeup to volume with reagent water.NOTE 7If only dissolved molybdenum is to be determined, filter portion of the sample through a 0.45-m membrane filter (8.17) and proceed with11.411.5.11.5 Pipette a volume of sample containing less than 2.5 g of molybdenum (100 mLmaximum) into a 200-mLvolumetric flaskand adjust the volume to 100 mL with water.11.6 Add 5 mL of ascorbic acid solution (8.3) and mix.11.7 Add 2 drops o
