1、Designation: D1068 10An American National StandardStandard 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
2、 in parentheses 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 Department of Defense.1. Scope*1.1 These test methods cover the determination of iron inwater.
3、 Procedures are given for 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 B
4、Atomic Absorption,Graphite 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 metho
5、ds were discontinued. See Appendix X2 for histori-cal information.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It i
6、s 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 3, 11.7.1, and X1.1.2.2. Referenced Documents2.1 ASTM Standards:2D858 Test Meth
7、ods 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 Zinc in WaterD1886 Test Methods for Nickel in WaterD2777 Practice fo
8、r 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 Practice for Measuring Trace Elements in Water byGraphite Furnace Atomic Abs
9、orption SpectrophotometryD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE60 Practice for Analy
10、sis of Metals, Ores, and RelatedMaterials by Molecular Absorption SpectrometryE275 Practice for Describing and Measuring Performanceof Ultraviolet and Visible Spectrophotometers3. Terminology3.1 Definitions: For definitions of terms used in these testmethods, refer to Terminology D1129.3.2 Definitio
11、ns of Terms Specific to This Standard:3.2.1 total recoverable iron, nan arbitrary analytical termrelating to the recoverable forms of iron that are determinableby the digestion method which is included in these testmethods.4. Significance and Use4.1 Iron is the second most abundant metallic element
12、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, the recommended limit for iron in domestic watersupplies is 0.3 mg/L. These test methods are useful
13、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 InorganicConstituents in Water.Current edition approved Sept. 1, 2010. Published October 2010. Originallyapproved in 194
14、9. Last previous edition approved in 2005 as D1068 051. DOI:10.1520/D1068-10.2For 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 ont
15、he ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Purity of Reagents5.1 Reagent grade chemicals shall be used in all tests.Unless otherwise indicated,
16、 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 used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its
17、 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 I. Other reagent water types maybe used, provided it is first ascertained that the water is ofsuf
18、ficiently 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 addition, water used in preparing solutions forthe determination of ferrous iron shall be freshly boile
19、d andessentially oxygen free.6. Sampling6.1 Collect the sample in accordance with Practice D1066or Practices D3370, as applicable.6.2 Samples should be preserved with HNO3or HCl (sp gr1.42) to a pH of 2 or less immediately at the time of collection.If only dissolved iron is to be determined, the sam
20、ple shall befiltered through a 0.45-m membrane filter before acidification.The holding time for samples can be calculated in accordancewith Practice D4841.6.3 If ferrous iron is to be determined, the sample should beanalyzed as soon as possible after collection and contact withatmospheric oxygen sho
21、uld 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 dissolvedand total recoverable iron in most waters and wastewaters.7.2 This test method is applicab
22、le 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, ground, and surface waters; unspecifiedwastewaters; and a refinery primary treatment water.
23、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 determined by atomizing the filteredsample directly with no pretreatment. Total recoverab
24、le 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), chromium (Test Methods D1687), cobalt(Test Methods D3558), copper (Test Methods D1688), lead(
25、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, nickel, copper, zinc, palladium, silver, cadmium, tin,lead, lithium, mercury, selenium
26、, 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 1Instrument manufacturers instructions for use of the specificcorrection technique should
27、 be followed.10. Apparatus10.1 Atomic Absorption Spectrophotometer, for use at 248.3nm.NOTE 2The manufacturers instructions should be followed for allinstrumental parameters. A wavelength other than 248.3 nm may be usedif it has been determined to be equally suitable.10.1.1 Iron Hollow-Cathode LampM
28、ultielement 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 controlled operating pressure of the instrument by suitablevalves.11. Reagents and Materials11.1
29、 Hydrochloric Acid (sp gr 1.19)Concentrated hydro-chloric acid (HCl).NOTE 3If the reagent blank concentration is greater than the methoddetection limit, distill the HCl or use a spectrograde acid. PrecautionWhen HCl is distilled an azeotropic mixture is obtained (approximately 6N HCl). Therefore, wh
30、en 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 4If the reagent blank concentration is greater than the methoddetection limit, distill the HN
31、O3or use a spectrograde acid.11.3 Nitric Acid (1 + 499)Add 1 volume of HNO3(sp gr1.42) to 499 volumes of water.11.4 Iron 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 stoc
32、k solutions are commercially available through chemi-cal supply vendors and may be used.11.5 Iron Solution, Standard (1 mL = 0.1 mg Iron)Dilute100.0 mL of the iron stock solution to 1 L with 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 10211.6 Oxida
34、nt: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 available acety-lene is the usual fuel. Acetone, always present in acetylenecylinders can affect analytical results. T
35、he cylinder should bereplaced at 50 psig (345 kPa). (Warning“Purified” gradeacetylene containing a special proprietary solvent rather thanacetone should not be used with poly vinyl chloride tubing asweakening of the tubing walls can cause a potentially hazard-ous situation.)12. Standardization12.1 P
36、repare 100 mL each of a blank and at least fourstandard solutions to bracket the expected iron concentrationrange of the samples to be analyzed by diluting the standardiron solution with HNO3(1 + 499). Prepare the standards eachtime the test is to be performed.12.2 When determining total recoverable
37、 iron add 0.5 mL ofHNO3(sp gr 1.42) and proceed as directed in 13.1 through13.5. When determining dissolved iron proceed as directed inNote 5, 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 curv
38、e by plotting the absorbanceversus concentration for each standard on linear graph paper.Alternatively 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 5If only disso
39、lved iron is to be determined, start with 13.5.13.2 Add 5 mL of HCl (sp gr 1.19) to each sample.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 6When analyzing samples of brin
40、es or samples containingappreciable amounts of suspended matter or dissolved solids, the amountof reduction in volume is left to the discretion of the analyst.13.4 Cool and filter the samples through a suitable filter(such as fine-textured, acid-washed, ashless paper), into100-mL volumetric flasks.
41、Wash the filter paper two or threetimes with water and adjust a volume.13.5 Aspirate each filtered and acidified sample and deter-mine its absorbance or concentration at 248.3 nm. AspirateHNO3(1 + 499) between each sample.14. Calculation14.1 Calculate the concentration of iron in the sample, inmilli
42、grams per litre, referring to 12.4.15. Precision and Bias415.1 The precision of this test method for 10 laboratories,which include 16 operations within its designated range may beexpressed as follows:Reagent Water Type II:ST5 0.047 X 1 0.053So5 0.030 X 1 0.037Water of Choice:ST5 0.050 X 1 0.114So5 0
43、.024 X 1 0.078where:ST= overall precision,So= single-operator precision, andX = determined concentration of iron, mg/L.15.2 Recoveries 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
44、and surface water; unspecified waste-water; and a refinery primary treatment water. It is the usersresponsibility to ensure the 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 collabora
45、tivetesting. Under the allowances made in 1.4 of PracticeD2777 08, these precision and bias data do meet existingrequirements of interlaboratory studies of Committee D19 testmethods.16. Quality Control16.1 In order to be certain that analytical values obtainedusing these test methods are valid and a
46、ccurate within theconfidence limits of the test, the following QC procedures mustbe followed when analyzing iron.16.2 Calibration and Calibration Verification:4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D19-1035.TABLE 1 Dete
47、rmination of Bias, Atomic Absorption, DirectReagent Water Type II:Bias, %StatisticallySignificant(95 %ConfidenceLevel)Amount Added,mg/LAmount Found,mg/LBias, mg/L0.2 0.2 60.0 0.0 no2.4 2.4 60.0 0.0 no4.4 4.3 0.1 2.3 yesNatural Water:Bias, %StatisticallySignificant(95 %ConfidenceLevel)Amount Added,mg
48、/LAmount Found,mg/LBias, mg/L0.2 0.2 60.0 0 no2.4 2.3 0.1 4.17 yes4.4 4.2 0.2 4.55 yesD1068 10316.2.1 Analyze at least three working standards containingconcentrations of iron that bracket the expected sample con-centration, prior to analysis of samples, to calibrate theinstrument. The calibration c
49、orrelation coefficient shall beequal to or greater than 0.990. In addition to the initialcalibration blank, a calibration blank shall be analyzed at theend of the batch run to ensure contamination was not a problemduring the batch analysis.16.2.2 Verify instrument calibration after standardization byanalyzing a standard at the concentration of one of thecalibration standards. The concentration of a mid-range stan-dard should fall within 615 % of the known concentration.16.2.3 If calibration cannot be verified, recalibrate theinstrume
