1、Designation: E 1615 05Standard Test Method forIron in Trace Quantities Using the FerroZine Method1This standard is issued under the fixed designation E 1615; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of iron in therange from 0.01 to 0.2 g/g using FerroZinet2reagent solu-tion. The range m
3、ay be extended through the use of a 5- or10-cm cell or by suitable dilution of the sample solution.1.2 This test method is intended to be general for the finalsteps in the determination of iron and does not includeprocedures for sample preparation.1.3 Review the current material safety data sheets (
4、MSDS)for detailed information concerning toxicity, first-aid proce-dures, and safety precautions.1.4 This standard does not purport to address 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
5、practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardsstatements, see 7.4.2. Referenced Documents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterE60 Practice for Photometric and SpectrophotometricMethods for Chemical Analysis of MetalsE 200
6、Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysisE 275 Practice for Determining and Measuring Perfor-mance of Ultraviolet, Visible, and Near Infrared Spectro-photometers3. Summary of Test Method3.1 This test method is based upon a photomet
7、ric determi-nation of the FerroZine complex with the iron (II) ion.4,5Thesample is dissolved in a suitable solvent and the iron is reactedwith FerroZine reagent solution which will convert the dis-solved iron compounds to form a magenta color iron (II)complex. The iron content of the sample solution
8、 is determinedby measurement of the magenta color at 560 nm using asuitable photometer.4. Significance and Use4.1 This test method is suitable for determining traceconcentrations of iron in a wide variety of products, providedthat appropriate sample preparation has rendered the iron andsample matrix
9、 soluble in water or other suitable solvent. Eachsample matrix must be investigated for suitability using thistest method.4.2 This test method assumes that the amount of colordeveloped is proportional to the amount of iron in the testsolution. The calibration curve is linear over the specifiedrange.
10、5. Interferences5.1 Any ion that absorbs light at 560 nm will interfere withthe determination. Anionic interferences include oxalate inconcentrations over 500 g/g, cyanide, and nitrate.45.2 Of copper, cobalt, calcium, magnesium, lead, silver,molybdenum, aluminum, nickel, zinc, arsenic, manganese,hex
11、avalent chromium, trivalent chromium, divalent cobalt andmonovalent copper are the only metals other than iron thatform colored species with FerroZine under test conditions. Atleast 1000 mg/L of the alkali metals and the alkaline earths hadno effect on the determination. Many heavy metals will react
12、with FerroZine in competition with iron, but with the excessreagent used in the test there is no effect on the results.45.3 The pH range of the final solution should be from 4 to9 to give the best test results.4,55.4 All glassware used in this test method must be iron-freeand scrupulously clean by p
13、recleaning with dilute hydrochloricacid and FerroZine reagent solution followed by a water rinse.6. Apparatus6.1 Photometer, capable of measuring light absorption at560 nm and holding a 5-cm or 10-cm cell. Check the1This test method is under the jurisdiction of ASTM Committee E15 onIndustrial and Sp
14、ecialty Chemicals and is the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved October 1, 2005. Published November 2005. Originallyapproved in 1994. Last previous edition approved in 2004 as E 1615 04.2FerroZine is a trademark of Hach Chemical Company.3For ref
15、erenced 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 website.4Stookey, L. L., “FerroZineA New Spectrophotometric Reagent for Iron,
16、”Analytical Chemistry, Vol 42, No. 7, June 1970, pp. 779 781.5Gibbs, C. R., “Characterization and Application of FerroZine Iron Reagent asa Ferrous Iron Indicator,” Analytical Chemistry, Vol 48, No. 8, July 1976, pp.11971201.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
17、shohocken, PA 19428-2959, United States.performance of the photometer at regular intervals according tothe guidelines given in Practice E 275 and the manufacturersmanual.6.2 Absorption Cells, 5-cm or 10-cm light path.NOTE 1A discussion of photometers and photometric practice isgiven in Practice E60.
18、7. Reagents7.1 Unless otherwise indicated, it is intended that all re-agents shall conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society, wheresuch specifications are available.6Other grades may be used,provided it is first ascertained that the reagent
19、 is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean Type II or Type IIIreagent water conforming to Specification D 1193.7.3 Iron, Standard Solution, 1 mL = 1
20、g Fe (see Note 2 andNote 3)Dissolve 0.1000 g of iron wire in 10 mL ofhydrochloric acid (HCl, 1 + 1) and 1 mL of saturated brominewater (400 mL water + 20 mL bromine). Boil until the excessbromine is removed. Add 200 mL of HCl, cool, and dilute to 1L in a volumetric flask. Dilute 10 mL of this soluti
21、on to 1 L.NOTE 2The preparation of this reagent is also described in PracticeE 200.NOTE 3As an alternative, the standard iron solution may be preparedby diluting 1.00 mL of commercially available iron standard stocksolution (1000 mg iron/L) to 1 L with water.7.4 FerroZine Reagent SolutionContains Fe
22、rroZine colorreagent 3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine, monosodium salt, monohydrate, buffer, and a reduc-ing agent. (WarningThis solution contains thiols as reduc-ing agents. Wear butyl rubber or neoprene gloves whenhandling the solution and avoid inhalation of the vapors.
23、)7.4.1 Alternatively, the individual solutions can be preparedas described below.47.4.1.1 Reducing AgentHydroxylamine hydrochloride, 10percent by weight solution in hydrochloric acid: Dissolve 10 gof reagent grade hydroxylamine hydrochloride (NH2OH.HCL)in 30 g of deionized water in a plastic bottle;
24、 add 50 mL ofreagent grade concentrated hydrochloric acid and mix well.Prepare this solution fresh daily.7.4.1.2 Color ReagentFerroZine, 0.514 weight percentsolution: Dissolve 0.514 g of FerroZine reagent in 100 g ofdeionized water in a plastic bottle, and mix well. Discard thereagent after seven da
25、ys.7.4.1.3 Buffer Reagent-pH 10.0 BufferDissolve 200 g ofreagent grade ammonium acetate in a minimum of deionizedwater, add 175 mL of concentrated ammonium hydroxide anddilute to 500 mL in a volumetric flask. Mix well. Check the pHof the buffer to verify that it is pH 10 6 0.5. If it is not in there
26、quired pH range, remake the buffer. Store the buffer in aplastic bottle. Discard after four weeks.8. Sampling8.1 Because this is a general test method for the final stepsin determining iron, specific procedures for sample preparationare not included (see 4.1 and 4.2).9. Calibration9.1 FerroZine Reag
27、ent Solution Method (7.4):9.1.1 By means of suitable pipets or a buret, transfer 0(reagent blank), 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, and 10.0 mL,respectively, of the standard iron solution and approximately20 mL of water to each of eight clean, dry, 50-mL, glass-stoppered volumetric flasks. These flasks
28、 represent 0, 0.5, 1.0,2.0, 4.0, 6.0, 8.0, and 10.0 g of iron. Add 2.0 mL of FerroZinereagent solution to each flask, dilute the contents of each flaskto volume with water, stopper, and mix well by inverting theflasks several times. Let the solutions stand for a minimum of5 min but not more than 10
29、min to develop the magenta color.Measure the absorbance of each calibration standard in accor-dance with 10.3.9.2 Individual Solution Method (7.4.1):9.2.1 By means of suitable pipets or a buret, transfer 0(reagent blank), 1.0, 2.0, 4.0, 6.0, 8.0, 10.0 and 20.0 mL,respectively, of the standard iron s
30、olution and approximately40 mL of water to each of eight clean, dry, 100-mL, glass-stoppered volumetric flasks. These flasks represent 0, 1.0, 2.0,4.0, 6.0, 8.0, 10.0 and 20.0 g of iron. Add the individualreagents (reducing reagent, color reagent and buffer reagent) asdescribed in 10.2 and 10.3 to e
31、ach flask, dilute the contents ofeach flask to volume with water, stopper, and mix well byinverting the flasks several times. Let the solutions stand for aminimum of 5 min but not more than 20 min to develop themagenta color. Measure the absorbance of each calibrationstandard in accordance with 10.3
32、.9.3 Plot, on linear graph paper, the micrograms of iron as afunction of absorbance.NOTE 4If the photometer readings are percent transmittance, theymay be plotted on semilog paper or converted to absorbance as follows:A 5 log 100/T! (1)where:A = absorbance, andT = transmittance, %.NOTE 5If desired,
33、the slope of the calibration line may be calculatedas follows:S 5 L 3 W (2)where:S = slope of calibration line, g Fecm/absorbance unit,L = cell path length, cm, andW = iron, g, corresponding to an absorbance of 1.000 on thecalibration line.NOTE 6Many spectrophotometers have the ability to calculate
34、acalibration graph automatically after measuring the calibration solutionsand subsequently to show the concentration of the component beingmeasured directly on a display. In such cases no manual calibration graphsneed to be constructed. It is, however, recommended to verify thecalculation procedure
35、of the instrument and to establish the characteristics6Reagent 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 LaboratoryChemicals, BDH Ltd.,
36、 Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.E1615052of the calibration graph according to suitable regression analysis software.NOTE 7The entire calibration graph is based on only one startingsolution (stand
37、ard iron solution). In such a case a weighing error, forexample, could introduce significant errors when reading concentrationsof test solutions. It is, therefore, recommended to prepare a separatelyweighed control solution containing an accurately known amount ofapproximately 5 g of iron. Measure t
38、he absorbance of this solutionaccording to 10.3. Obtain the iron concentration of the control solutionfrom the calibration graph/function. If this value and the calculated valueof the control solution differ by more than5%oftheir mean, repeat thecalibration.10. Procedure10.1 FerroZine Reagent Soluti
39、on Method (7.4):10.1.1 Weigh to three significant figures a sample contain-ing 0.5 to 10 g of iron into a clean, dry 50-mL, glass-stoppered, volumetric flask (see Note 8). Add sufficient waterto dissolve the sample but do not exceed 40 mL total volume.NOTE 8Preliminary tests must be made to determin
40、e if the sample orany impurities in the sample interfere in any way with the analysis.10.1.2 To prepare a reagent blank, add about 20 mL of waterto a second clean, dry, 50-mL, glass-stoppered, volumetricflask.NOTE 9When running a number of samples, only one reagent blankis needed.10.1.3 Add 2.0 mL o
41、f the FerroZine reagent solution to eachvolumetric flask, stopper, and swirl to mix the contents. Diluteeach volumetric flask to volume with water, stopper, and mixwell by inverting the flask several times. The pH range of thefinal solution should be 4 to 9 to give the best test results.4,5Allow the
42、 sample solution and reagent blank to equilibrate atroom temperature for a minimum of 5 min for color develop-ment.10.2 Individual Solution Method (7.4.1):10.2.1 Weigh 80.0 g of sample to the nearest 0.01 g into a100 mL glass-stoppered volumetric flask. Add 80 mL ofdeionized water to a second volume
43、tric flask and reserve as areagent blank.10.2.2 Pipet 2 mL of the hydroxylamine hydrochloridesolution and 2 mL of the FerroZine solution into each of theflasks, stopper, and mix well by inverting several times. Do notshake.10.2.3 After 5 min, pipet 2 mL of the buffer into each flask,stopper, and mix
44、 well by inverting several times. Do not shake.Make up to 100 mL with deionized water. Mix well byinverting several times; do not shake. The pH of the solutionshould be in the range of 4 to 9. Color development will not becomplete outside of this pH range.10.2.4 Allow color development for at least
45、5 min. Measurethe absorbance of the sample relative to the reagent blank at themaximum absorbance (560 nm) as in 10.3. Absorbance mea-surement should be completed within 20 min of adding thebuffer.10.2.5 If the absorbance of the sample is greater than thehighest standard (20 g of iron, (9.2.1) in th
46、e calibrationcurve, reduce the sample size so that the absorbance of thesample is within the calibration curve. Repeat the procedures in10.2 using the reduced sample size.NOTE 10When using a 10-cm cell, the sample size for samplescontaining from 0.1 to 1 g/g iron should be 8 g and for samplescontain
47、ing from 1 to 10 g/g iron the sample size should be 1 g.NOTE 11The 80 g of sample in 100 mLs is proportionally the same asthe maximum of 40 g of sample in 50 mLs in 10.1.10.3 Measure the absorbance of each sample solution at 560nm in a 5-cm or 10-cm cell using a suitable photometer. Use amatched cel
48、l filled with the reagent blank to set the instrumentat zero absorbance or 100 % transmittance.10.4 Refer to a previously prepared calibration curve todetermine the micrograms of iron found.10.5 Qualtiy ControlIt is recommended that a controlchart for an aqueous quality control sample of well establ
49、ishediron concentration be established and maintained according togenerally accepted guidelines.7Measure the control sampleeach time a (series of) test sample(s) is tested. If the measuredvalue exceeds the action limit of the control chart, takeappropriate action before proceeding with sample tests.11. Calculation11.1 Calculate the iron content of the sample, g/g, asfollows (see Note 12):iron 5 B/W (3)where:B = iron found, g, andW = sample, g.NOTE 12If the slope of the calibration line has been calculated, themicrograms of iron, B, may be ca
