1、Designation: D1068 15Standard Test Methods forIron in Water1This standard is issued under the fixed designation D1068; 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 indicates the
2、 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 These test methods cover the determination of iron inwater. Procedures are given fo
3、r determining total iron, dis-solved iron, and ferrous iron. Undissolved iron may becalculated from the total iron and dissolved iron determina-tions. The test methods are given as follows:Range SectionsTest Method AAtomic Absorption,Direct0.1 to 5.0 mg/L 7 to 16Test Method BAtomic Absorption,Graphi
4、te Furnace5 to 100 g/L 17 to 26Test Method CPhotometricBathophenanthroline g/L40 to 1000 g/L 27 to 381.2 It is the users responsibility to ensure the validity ofthese test methods to waters of untested matrices.1.3 The chelation-extraction and two former photometrictest methods were discontinued. Se
5、e Appendix X2 for histori-cal information.1.4 The values stated in SI units are to be regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.5 This standard does not purport to add
6、ress 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. Specific hazardsstatements are given in Note 4, 11.7.1,
7、 and X1.1.2.2. Referenced Documents2.1 ASTM Standards:2D858 Test Methods for Manganese in WaterD1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD1687 Test Methods for Chromium in WaterD1688 Test Methods for Copper in WaterD1691 Test Methods for
8、 Zinc in WaterD1886 Test Methods for Nickel in WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3558 Test Methods for Cobalt in WaterD3559 Test Methods for Lead in WaterD3919 Practic
9、e for Measuring Trace Elements in Water byGraphite Furnace Atomic Absorption SpectrophotometryD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5673 Test Method for Elements in Water by InductivelyCoupled PlasmaMass SpectrometryD5810 Guide f
10、or Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE60 Practice for Analysis of Metals, Ores, and RelatedMaterials by SpectrophotometryE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spe
11、ctrophotometers3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 total recoverable iron, na descriptive term relatingto the iron forms recovered in the acid-digestion procedurespecifi
12、ed in these test methods.4. Significance and Use4.1 Iron is the second most abundant metallic element in theearths crust and is essential in the metabolism of plants andanimals. If presented in excessive amounts, however, it formsoxyhydroxide precipitates that stain laundry and porcelain. Asa result
13、, the recommended limit for iron in domestic watersupplies is 0.3 mg/L. These test methods are useful fordetermining iron in many natural waters.1These test methods are under the jurisdiction of ASTM Committee D19 onWater and are the direct responsibility of Subcommittee D19.05 on InorganicConstitue
14、nts in Water.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in 1949. Last previous edition approved in 2010 as D1068 10. DOI:10.1520/D1068-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. F
15、or Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*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 States15. Pu
16、rity of Reagents5.1 Reagent grade chemicals shall be used in all tests.Unless otherwise indicated, it is intended that all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society, where suchspecifications are available.3Other grades may be
17、used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.5.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D1193, Type
18、 I. Other reagent water types maybe used, provided it is first ascertained that the water is ofsufficiently high purity to permit its use without adverselyaffecting the bias and precision of the test method. Type IIwater was specified at the time of round-robin testing of thesetest methods. In addit
19、ion, water used in preparing solutions forthe determination of ferrous iron shall be freshly boiled andessentially oxygen free.6. Sampling6.1 Collect the sample in accordance with Practices D1066or D3370, as applicable.6.2 Samples should be preserved with HNO3or HCl (sp gr1.42) to a pH of 2 or less
20、immediately at the time of collection.If only dissolved iron is to be determined, the sample shall befiltered through a 0.45-m membrane filter before acidification.The holding time for samples can be calculated in accordancewith Practice D4841.NOTE 1Alternatively, the pH may be adjusted in the labor
21、atory if thesample is returned within 14 days. However, acid must be added at least24 hours before analysis to dissolve any metals that adsorb to the containerwalls. This could reduce hazards of working with acids in the field whenappropriate.6.3 If ferrous iron is to be determined, the sample shoul
22、d beanalyzed as soon as possible after collection and contact withatmospheric oxygen should be minimized.6.4 Additional information on sampling requirements forTest Method C is provided in 33.1.TEST METHOD AATOMIC ABSORPTION, DIRECT7. Scope7.1 This test method covers the determination of dissolvedan
23、d total recoverable iron in most waters and wastewaters.7.2 This test method is applicable in the range from 0.1 to5.0 mg/L of iron. The range may be extended to concentrationsgreater than 5.0 mg/L by dilution of the sample.7.3 This test method has been used successfully withreagent water; tap, grou
24、nd, and surface waters; unspecifiedwastewaters; and a refinery primary treatment water. It is theusers responsibility to ensure the validity of this test methodfor waters of untested matrices.8. Summary of Test Method8.1 Iron is determined by atomic absorption spectrophotom-etry. Dissolved iron is d
25、etermined by atomizing the filteredsample directly with no pretreatment. Total recoverable iron isdetermined by atomizing the sample following hydrochloric-nitric acid digestion and filtration. The same digestion proce-dure may be used to determine total recoverable nickel (TestMethods D1886), chrom
26、ium (Test Methods D1687), cobalt(Test Methods D3558), copper (Test Methods D1688), lead(Test Methods D3559), manganese (Test Methods D858), andzinc (Test Methods D1691).9. Interferences9.1 Sodium, potassium, barium, chloride and sulfate (5000mg/L each), calcium, magnesium, chromium, manganese,cobalt
27、, nickel, copper, zinc, palladium, silver, cadmium, tin,lead, lithium, mercury, selenium, aluminum, antimony, arsenic,vanadium, boron, and molybdenum (100 mg/L) do not inter-fere.9.2 Background correction (or chelation-extraction) may benecessary to determine low levels of iron in some waters.NOTE 2
28、Instrument manufacturers instructions for use of the specificcorrection technique should be followed.10. Apparatus10.1 Atomic Absorption Spectrophotometer, for use at 248.3nm.NOTE 3The manufacturers instructions should be followed for allinstrumental parameters. A wavelength other than 248.3 nm may
29、be usedif it has been determined to be equally suitable.10.1.1 Iron Hollow-Cathode LampMultielement hollow-cathode lamps are available and have also been found satis-factory.10.2 Pressure-Reducing ValvesThe supplies of fuel andoxidant shall be maintained at pressures somewhat higher thanthe controll
30、ed operating pressure of the instrument by suitablevalves.11. Reagents and Materials11.1 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl).NOTE 4If the reagent blank concentration is greater than the methoddetection limit, distill the HCl or use a spectrograde acid. (WarningWhen HC
31、l is distilled an azeotropic mixture is obtained (approximately 6N HCl). Therefore, when concentrated HCl is specified for the preparationof reagents or in the procedure, use double the volume specified if distilledacid is used.)11.2 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).NOTE 5If th
32、e reagent blank concentration is greater than the methoddetection limit, distill the HNO3or use a spectrograde acid.11.3 Nitric Acid (1 + 499)Add 1 volume of HNO3(sp gr1.42) to 499 volumes of water.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC
33、. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.D1068 15211.4 Iron
34、 Solution, Stock (1 mL = 1.0 mg Iron)Dissolve1.000 g of pure iron in 100 mL of HCL (1 + 1) with the aid ofheat. Cool and dilute to 1 L with water. Alternatively, certifiediron stock solutions of appropriate known purity are commer-cially available through chemical supply vendors and may beused.11.5
35、Iron Solution, Standard (1 mL = 0.1 mg Iron)Dilute100.0 mL of the iron stock solution to 1 L with water.11.6 Oxidant:11.6.1 Air, which has been passed through a suitable filter toremove oil, water, and other foreign substances is the usualoxidant.11.7 Fuel:11.7.1 AcetyleneStandard, commercially avai
36、lable acety-lene is the usual fuel. Acetone, always present in acetylenecylinders can affect analytical results. The cylinder should bereplaced at 345 kPa (50 psig). (Warning“Purified” gradeacetylene containing a special proprietary solvent rather thanacetone should not be used with poly vinyl chlor
37、ide tubing asweakening of the tubing walls can cause a potentially hazard-ous situation.)11.8 Filter PaperPurchase suitable filter paper. Typicallythe filter papers have a pore size of 0.45-m membrane.Material such as fine-textured, acid-washed, ashless paper, orglass fiber paper are acceptable. The
38、 user must first ascertainthat the filter paper is of sufficient purity to use withoutadversely affecting the bias and precision of the test method.12. Standardization12.1 Prepare 100 mL each of a blank and at least fourstandard solutions to bracket the expected iron concentrationrange of the sample
39、s to be analyzed by diluting the standardiron solution with HNO3(1 + 499). Prepare the standards eachtime the test is to be performed or as determined by PracticeD4841.12.2 When determining total recoverable iron add 0.5 mL ofHNO3(sp gr 1.42) and proceed as directed in 13.1 through13.5. When determi
40、ning dissolved iron proceed as directed inNote 6, 13.1.12.3 Aspirate the blank and standards and record the instru-ment readings. Aspirate HNO3(1 + 499) between each stan-dard.12.4 Prepare an analytical curve by plotting the absorbanceversus concentration for each standard on linear graph paper.Alte
41、rnatively read directly in concentration if this capability isprovided with the instrument.13. Procedure13.1 Measure 100.0 mL of a well-mixed acidified sampleinto a 125-mL beaker or flask.NOTE 6If only dissolved iron is to be determined, start with 13.5.13.2 Add 5 mL of HCl (sp gr 1.19) to each samp
42、le.13.3 Heat the samples on a steam bath or hotplate in awell-ventilated hood until the volume has been reduced to 15to 20 mL, making certain that the samples do not boil.NOTE 7When analyzing samples of brines or samples containingappreciable amounts of suspended matter or dissolved solids, the amou
43、ntof reduction in volume is left to the discretion of the analyst.NOTE 8Many laboratories have found block digestion systems auseful way to digest samples for trace metals analysis. Systems typicallyconsist of either a metal or graphite block with wells to hold digestiontubes. The block temperature
44、controller must be able to maintain unifor-mity of temperature (65C to 85C) across all positions of the block. Fortrace metals analysis, the digestion tubes should be constructed ofpolypropylene and have a volume accuracy of at least 0.5 %. All lots oftubes should come with a certificate of analysis
45、 to demonstrate suitabilityfor their intended purpose.13.4 Cool and filter the samples through a suitable filter(11.8) (such as fine-textured, acid-washed, ashless paper), into100-mL volumetric flasks. Wash the filter paper two or threetimes with water and adjust a volume.13.5 Utilize sample from 13
46、.4 and determine its absorbanceor concentration at 248.3 nm. Aspirate HNO3(1 + 499)between each sample.14. Calculation14.1 Calculate the concentration of iron in the sample, inmilligrams per litre, referring to 12.4.15. Precision and Bias415.1 The precision of this test method for 10 laboratories,wh
47、ich include 16 operations within its designated range may beexpressed as follows:Reagent Water Type II:ST5 0.047 X10.053So5 0.030 X10.037Water of Choice:ST5 0.050 X10.114So5 0.024 X10.078where:ST= overall precision,So= single-operator precision, andX = determined concentration of iron, mg/L.15.2 Rec
48、overies of known amounts of iron in a series ofprepared standards were as shown in Table 1.15.3 The collaborative test data were obtained on reagentwater; tap, lake, ground and surface water; unspecified waste-water; and a refinery primary treatment water. It is the usersresponsibility to ensure the
49、 validity of this test method forwaters of untested matrices.15.4 This section on precision and bias conforms to PracticeD2777 77 which was in place at the time of collaborativetesting. Under the allowances made in 1.4 of PracticeD2777 13, these precision and bias data do meet existingrequirements of interlaboratory studies of Committee D19 testmethods.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D19-1035. ContactASTM CustomerService at serviceastm.org.D1068 15316
