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2、n American National StandardStandard Test Methods forIron in Water1This standard is issued under the fixed designation D 1068; 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 indic
3、ates 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.1. Scope*1.1 These test methods cover the determination of iron in water. Procedures are giv
4、en for determining total iron, dis- solved iron, and ferrous iron. Undissolved iron may be calculated from the total iron and dissolved iron determina- tions. The test methods are given as follows:RangeSectionsApplicable Methods of Committee D-19 on Water2D 3370 Practices for Sampling Water from Clo
5、sed Con- duits2D 3558 Test Methods for Cobalt in Water2D 3559 Test Methods for Lead in Water2D 3919 Practice for Measuring Trace Elements in Water byGraphite Furnace Atomic Absorption Spectrophotometry2Test Method AAtomic Absorption,DirectTest Method CAtomic Absorption, Graphite FurnaceTest Method D
6、PhotometricBathophenanthroline g/L0.1 to 5.0 mg/L7 to 155 to 100 g/L16 to 2440 to 1000 g/L25 to 36D 4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic Constituents2D 5810 Guide for Spiking into Aqueous Samples3D 5847 Practice for the Writing Quality Contro
7、l Specifica- tions for Standard Test Methods for Water Analysis31.2 It is the users responsibility to ensure the validity ofthese test methods to waters of untested matrices.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsib
8、ility 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 hazards statements are given in Note 3, Note 5, and Note X1.1.1.4 Two former photometric test methods were discontin- ued. See
9、Appendix X2 for historical information.2. Referenced Documents2.1 ASTM Standards:D 858 Test Methods for Manganese in Water2D 1066 Practice for Sampling Steam2D 1129 Terminology Relating to Water2D 1192 Specification for Equipment for Sampling Water and Steam in Closed Conduits2D 1193 Specification f
10、or Reagent Water2D 1687 Test Methods for Chromium in Water2D 1688 Test Methods for Copper in Water2D 1691 Test Methods for Zinc in Water2D 1886 Test Methods for Nickel in Water2D 2777 Practice for Determination of Precision and Bias of1 These test methods are under the jurisdiction of ASTM Committee
11、 D19 on Water and are the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.E 60 Practice for Photometric and SpectrophotometricMethods for Chemical Analysis of Metals3E 275 Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near Infrared Spe
12、ctrophotom- eters43. Terminology3.1 Definitions: For definitions of terms used in these test methods, refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 total recoverable ironan arbitrary analytical term relating to the recoverable forms of iron that are determinabl
13、e by the digestion method which is included in these test methods.4. Significance and Use4.1 Iron is the second most abundant metallic element in the earths crust and is essential in the metabolism of plants and animals. If presented in excessive amounts, however, it forms oxyhydroxide precipitates
14、that stain laundry and porcelain. Asa result, the recommended limit for iron in domestic water supplies is 0.3 mg/L. These test methods are useful for determining iron in many natural waters.5. Purity of Reagents5.1 Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it i
15、s intended that all reagents shall conform to the specifications of the Committee on AnalyticalCurrent edition approved Jan. 10, 2003. Published January 2003. Originally approved in 1949. Last previous edition approved in 1996 as D 1068 96.2 Annual Book of ASTM Standards, Vol 11.01.3 Annual Book of
16、ASTM Standards, Vol 03.05.4 Annual Book of ASTM Standards, Vol 03.06.*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.1D 1068 03 Reagents of the American Chemical Societ
17、y, where suchspecifications are available. 5 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.5.2 Purity of WaterUnless otherwise indicated, references to water shall be un
18、derstood to mean reagent water conforming to Specification D 1193, Type I. Other reagent water types may be used, provided it is first ascertained that the water is of sufficiently high purity to permit its use without adversely affecting the bias and precision of the test method. Type II water was
19、specified at the time of round-robin testing of these test methods. In addition, water used in preparing solutions for the determination of ferrous iron shall be freshly boiled and essentially oxygen free.6. Sampling6.1 Collect the sample in accordance with Practice D 1066, Specification D 1192, or
20、Practices D 3370, as applicable.6.2 Samples should be preserved with HNO3 or 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 sample shall be filtered through a 0.45-m membrane filter before acidification. The holding time for
21、 samples can be calculated in accordance with Practice D 4841.6.3 If ferrous iron is to be determined, the sample should be analyzed as soon as possible after collection and contact with atmospheric oxygen should be minimized.6.4 Additional information on sampling requirements forTest Method D is pr
22、ovided in 34.1.TEST METHOD AATOMIC ABSORPTION, DIRECT7. Scope7.1 This test method covers the determination of dissolved and 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 concentrations g
23、reater than 5.0 mg/L by dilution of the sample.7.3 This test method has been used successfully with reagent water; tap, ground, and surface waters; unspecified wastewaters; and a refinery primary treatment water. It is the users responsibility to ensure the validity of this test method for waters of
24、 untested matrices.8. Summary of Test Method8.1 Iron is determined by atomic absorption spectrophotom- etry. Dissolved iron is determined by atomizing the filtered sample directly with no pretreatment. Total recoverable iron is determined by atomizing the sample following hydrochloric- nitric acid d
25、igestion and filtration. The same digestion proce- dure may be used to determine total recoverable nickel (Test5 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Soci
26、ety, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.Methods D 1886), chromium (Test Methods D 1687), cobalt(Test Methods D 3558), copper (Test Methods
27、D 1688), lead(Test Methods D 3559), manganese (Test Methods D 858), and zinc (Test Methods D 1691).9. Interferences9.1 Sodium, potassium, barium, chloride and sulfate (5000 mg/L each), calcium, magnesium, chromium, manganese, cobalt, nickel, copper, zinc, palladium, silver, cadmium, tin, lead, lithi
28、um, mercury, selenium, aluminum, antimony, arsenic, vanadium, boron, and molybdenum (100 mg/L) do not inter- fere.9.2 Background correction (or chelation-extraction) may be necessary to determine low levels of iron in some waters.NOTE 1Instrument manufacturers instructions for use of the specific co
29、rrection technique should be followed.10. Apparatus10.1 Atomic Absorption Spectrophotometer, for use at 248.3nm.NOTE 2The manufacturers instructions should be followed for all instrumental parameters. A wavelength other than 248.3 nm may be usedif it has been determined to be equally suitable.10.1.1
30、 Iron Hollow-Cathode LampMultielement hollow- cathode lamps are available and have also been found satis- factory.10.2 Pressure-Reducing ValvesThe supplies of fuel and oxidant shall be maintained at pressures somewhat higher than the controlled operating pressure of the instrument by suitable valves
31、.11. Reagents and Materials11.1 Hydrochloric Acid (sp gr 1.19)Concentrated hydro- chloric acid (HCl).NOTE 3If the reagent blank concentration is greater than the method detection limit, distill the HCl or use a spectrograde acid. Precaution When HCl is distilled an azeotropic mixture is obtained (ap
32、proximately 6N HCl). Therefore, when concentrated HCl is specified for the preparation of reagents or in the procedure, use double the volume specified if distilled acid is used.11.2 Nitric Acid (sp gr 1.42)Concentrated nitric acid(HNO3).NOTE 4If the reagent blank concentration is greater than the m
33、ethod detection limit, distill the HNO3 or 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 of heat. Cool and dilute to 1 L with
34、water.11.5 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 to remove oil, water, and other foreign substances is the usual oxidant.11.7 Fuel:11.7.1 AcetyleneStandard, comm
35、ercially available acety- lene is the usual fuel. Acetone, always present in acetylene2D 1068 03 cylinders can affect analytical results. The cylinder should bereplaced at 50 psig (345 kPa).NOTE 5Warning: “Purified grade acetylene containing a special proprietary solvent rather than acetone should n
36、ot be used with poly vinyl chloride tubing as weakening of the tubing walls can cause a potentially hazardous situation.Water of Choice:ST 5 0.047 X 1 0.053S o 5 0.030 X 1 0.037ST 5 0.050 X 1 0.11412. Standardization12.1 Prepare 100 mL each of a blank and at least four standard solutions to bracket
37、the expected iron concentration range of the samples to be analyzed by diluting the standardwhere:So5 0.024 X 1 0.078ST = overall precision,iron solution with HNO3 (1 + 499). Prepare the standards eachtime the test is to be performed.So= single-operator precision, and12.2 When determining total reco
38、verable 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 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 anal
39、ytical curve by plotting the absorbance versus concentration for each standard on linear graph paper. Alternatively read directly in concentration if this capability is provided with the instrument.13. Procedure13.1 Measure 100.0 mL of a well-mixed acidified sample into a 125-mL beaker or flask.NOTE
40、 6If only dissolved iron is to be determined, start with 13.3.13.2 Add 5 mL of HCl (sp gr 1.19) to each sample.13.3 Heat the samples on a steam bath or hotplate in a well-ventilated hood until the volume has been reduced to 15 to 20 mL, making certain that the samples do not boil.NOTE 7When analyzin
41、g samples of brines or samples containing appreciable amounts of suspended matter or dissolved solids, the amount of 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
42、volumetric flasks. Wash the filter paper two or three times 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. Aspirate HNO3 (1 + 499) between each sample.14. CalculationX= determined concentration of iron, mg/
43、L.15.2 Recoveries of known amounts of iron in a series of prepared standards were as shown in Table 1.15.3 The collaborative test data were obtained on reagent water; tap, lake, ground and surface water; unspecified waste- water; and a refinery primary treatment water. It is the users responsibility
44、 to ensure the validity of this test method for waters of untested matrices.15.4 This section on precision and bias conforms to Practice D 2777 77 which was in place at the time of collaborative testing. Under the allowances made in 1.4 of D 2777 98, these precision and bias data do meet existing re
45、quirements of interlaboratory studies of Committee D19 test methods.16. Quality Control16.1 In order to be certain that analytical values obtained using these test methods are valid and accurate within the confidence limits of the test, the following QC procedures must be followed when analyzing iro
46、n.16.2 Calibration and Calibration Verification:16.2.1 Analyze at least three working standards containing concentrations of iron that bracket the expected sample con- centration, prior to analysis of samples, to calibrate the instrument. The calibration correlation coefficient shall be equal to or greater than 0.990. In addition to the initi