1、Designation: D 3868 04Standard Test Method forFluoride Ions in Brackish Water, Seawater, and Brines1This standard is issued under the fixed designation D 3868; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method2covers the determination of solublefluoride ions in brackish water, seawater and brines by use ofa fluoride se
3、lective electrode.1.2 Samples containing from 1.0 to 25 mg/L can be ana-lyzed by this test method.1.3 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
4、 practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on Wat
5、erD 3370 Practices for Sampling Water from Closed ConduitsD 5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1129.4. Summary of Test Method4.1 A fl
6、uoride selective electrode, reference electrode, andmillivoltmeter are used to determine fluoride in brine samplesby a standard addition method.4.2 The fluoride selective electrode consists of a lanthanumfluoride crystal that develops an electrode potential corre-sponding to the level of fluoride io
7、n in solution.5. Significance and Use5.1 Identification of a brackish water, seawater, or brine isdetermined by comparison of the concentrations of theirdissolved constituents. The results are used to evaluate theorigin of the water, determine if it is a possible pollutant, or ifit is related to a p
8、otential source of a valuable mineral. Forexample, in geochemical studies some correlation data indicatethat fluoride is an indirect indicator of the presence of lithium.6. Interferences6.1 Metal ions such as aluminum and iron (III) interferewith the fluoride determination by forming complexes withf
9、luoride ions. The buffer solution contains a complexing agentthat preferentially complexes these metal ions. This solutionalso contains a pH buffer to reduce electrode interference fromhydroxide ions and to prevent the formation of HF. Sodiumchloride is added as ionic strength adjustor. Increasing a
10、mountsof aluminum, iron (III), and borate ions were added to 1.5mg/Lfluoride solutions and were found not to interfere up to 5,350, and 250 mg/L (as boron), respectively.7. Apparatus7.1 Millivoltmeter (accurate to 6 0.1 mV), specific ionmeter.NOTE 1A specific ion meter that directly reads concentrat
11、ion may beused.7.2 Fluoride Selective Electrode, reference electrode.7.3 Microlitre Pipets.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommitee D19.05 on Inorganic Constituents inWater.Current edition approved March 1, 2004. Publis
12、hed April 2004. Originallyapproved in 1979. Last previous edition approved in 1999 as D 3868 95 (1999).2Additional information is contained in the following references: Hoke, S. H.,Fletcher, G. E., and Collins, A. G., “Fluoride and Iodide Selective ElectrodesApplied to Oilfield Brine Analysis,” U.S.
13、 Department of Energy, Report ofInvestigations, BETC/RI-78/7.Rix, C. J., Bond, A. M., and Smith, J. D., “District Determination of Fluoride inSea Water with a Fluoride Selective Ion Electrode by a Method of StandardAdditions,” Analytical Chemistry, Vol 48, 1976, p. 1236.3For referenced ASTM standard
14、s, 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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM Internat
15、ional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specification of the Committeeon Analytical
16、Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Purity of Water Unless otherwise indica
17、ted, referenceto water shall be understood to mean reagent water conformingto Specification D 1193, Type 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 precision and bias of the te
18、st method. Type IIIwater was specified at the time of round robin testing of thistest method.8.3 Buffer Solution5Dissolve 58 g of NaCl, 4 g of CDTAcomplexing agent (cyclohexylene dinitrilo tetraacetic acid),and 57 mL of glacial acetic acid in 500 mL of water. Slowlyadd NaOH solution (200 g/L) to adj
19、ust the pH of the solutionto 5.0 to 5.5 while cooling in a water bath. Transfer solution toa 1-L volumetric flask and dilute to the mark with water.8.4 Fluoride Solution, Standard (1 mL = 2 mg F)Dissolve 4.420 g of NaF in water and dilute to 1 L and store ina polyethylene bottle. This solution will
20、contain 2000 mg of F/L.9. Sampling9.1 Collect the sample in accordance with Practices D 3370.10. Procedure10.1 Pipet an aliquot of a brine sample containing 0.01 to0.03 mg of fluoride into a 125-mL polyethylene beaker and ifnecessary add water to make the total volume equal 40 mL.Add 40 mL of buffer
21、 solution. Place electrodes in the solutionto a depth of 30 mm. Stir solution for 5 min or until equilibriumis reached. Stop the stirrer and record the potential. Add 20 Lof the standard fluoride solution, stir solution for 3 min, andrecord the second potential under quiet conditions. Repeat theabov
22、e step for the second addition.11. Calculation11.1 Calculate the slope of the electrode as follows:Slope 5EB2 EAlog B 2 log A(1)where:A and B = two fluoride solutions of known concentration,mg/L,EA= electrode potential of Solution A mV, andEB= electrode potential of Solution B,mV.NOTE 2The slope of
23、the electrode should meet the manufacturersspecifications.11.2 Calculate the concentration of fluoride in the sample asfollows:2A 5 mg/L 5XfantilogSDEslopeD2 13 1000 (2)where:X = change in concentration upon addition of standard.(mg Fadded per 80 mL of solution),f = dilution factor (80 mL/mL of samp
24、le), andDE = change in potential resulting from addition of stan-dard.From the above procedure, two A values can be calculatedand averaged for each sample.12. Precision and Bias612.1 The precision of the test method within its designatedrange may be expressed as follows:ST5 0.08X 1 0.73 (3)Sc5 0.063
25、X 1 0.097where:ST= overall precision,So= single-operator precision, andX = concentration of fluoride determined, mg/L.12.2 The bias of the test method determined from recover-ies of known amounts of fluoride in a series of preparedstandards as shown in Table 1.NOTE 3The above precision and bias esti
26、mates are based on aninterlaboratory study on four artificial brine samples containing variousamounts of fluoride and interfering ions as shown in Table 2. One analystin each of three laboratories and two analysts in each of four laboratoriesperformed duplicate determinations on each of two days. Pr
27、actice D 2777was used in developing these precision and bias estimates.12.3 Precision and bias for this test method conforms toPractice D 277777, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 of D277798, these precision and bias data do meet existingrequire
28、ments for interlaboratory studies of Committee D19 testmethods.13. Quality Control13.1 In order to be certain that analytical values obtainedusing these test methods are valid and accurate within theconfidence limits of the test, the following QC procedures mustbe followed when analyzing fluoride.13
29、.2 Calibration and Calibration Verification13.2.1 Determine the slope of the electrode. The slopeshould meet the manufacturers specifications.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted b
30、y 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.5Also available as TISAB II from Orion Research Inc.6Supporting data are a
31、vailable from ASTM Headquarters. Request RR:D19-1060.D 3868 04213.2.2 Verify the electrode by analyzing a sample at theconcentration near the mid-range should fall within 6 15% ofthe known concentration.13.2.3 If calibration cannot be verified, recalibrate theinstrument.13.3 Initial Demonstration of
32、 Laboratory Capability13.3.1 If a laboratory has not performed the test before, or ifthere has been a major change in the measurement system, forexample, new analyst, new instrument, and so forth, a precisionand bias study must be performed to demonstrate laboratorycapability.13.3.2 Analyze seven re
33、plicates of a standard solutionprepared from an Independent Reference Material containing amid-range concentration of fluoride. The matrix and chemistryof the solution should be equivalent to the solution used in thecollaborative study. Each replicate must be taken through thecomplete analytical tes
34、t method including any sample preser-vation and pretreatment steps. The replicates may be inter-spersed with samples.13.3.3 Calculate the mean and standard deviation of theseven values and compare to the acceptable ranges of bias insection Table 1. This study should be repeated until therecoveries a
35、re within the limits given in Table 1. If a concen-tration other than the recommended concentration is used, referto Test Method D5847 for information on applying the F testand t test in evaluating the acceptability of the mean andstandard deviation.13.4 Laboratory Control Sample (LCS)13.4.1 To ensu
36、re that the test method is in control, analyzea LCS containing a mid-range concentration of fluoride witheach batch or ten samples. If large numbers of samples areanalyzed in the batch, analyze the LCS after every ten samples.The LCS must be taken through all of the steps of the analyticalmethod inc
37、luding sample preservation and pretreatment. Theresult obtained for the LCS shall fall within 6 15%oftheknown concentration.13.4.2 If the result is not within these limits, analysis ofsamples is halted until the problem is corrected, and either allthe samples in the batch must be reanalyzed, or the
38、results mustbe qualified with an indication that they do not fall within theperformance criteria of the test method.13.5 Method Blank13.5.1 Analyze a reagent water test blank with each batch.The concentration of fluoride found in the blank should be lessthan 1.0 mg/L. If the concentration of fluorid
39、e is found abovethis level, analysis of samples is halted until the contaminationis eliminated, and a blank shows no contamination at or abovethis level, or the results must be qualified with an indicationthat they do not fall within the performance criteria of the testmethod.13.6 Matrix Spike (MS)1
40、3.6.1 Flouride is not an analyte that can be feasibly spikedinto samples.13.7 Duplicate13.7.1 To check the precision of sample analyses, analyze asample in duplicate with each batch. If the concentration of theanalyte is less than five times the detection limit for the analyte,a matrix spike duplica
41、te (MSD) should be used.13.7.2 Calculate the standard deviation of the duplicatevalues and compare to the precision in the collaborative studyusing an F test. Refer to 6.4.4 of Test Method D 5847 forinformation on applying the F test.13.7.3 If the result exceeds the precision limit, the batchmust be
42、 reanalyzed or the results must be qualified with anindication that they do not fall within the performance criteriaof the test method.13.8 Independent Reference Material (IRM)13.8.1 In order to verify the quantitative value produced bythe test method, analyze an Independent Reference Material(IRM)
43、submitted as a regular sample (if practical) to thelaboratory at least once per quarter. The concentration of theIRM should be in the concentration mid-range for the methodchosen. The value obtained must fall within the control limitsestablished by the laboratory.14. Keywords14.1 analysis; brines; e
44、lectrode; fluorideTABLE 1 Determination of Precision and BiasAmount Addedmg/LAmount Foundmg/LStmg/LSomg/LBias%3.03 3.68 1.051 0.439 + 21.44.09 5.89 1.208 0.253 + 44.119.4 12.14 1.596 0.972 37.420.5 23.42 2.383 1.570 + 14.2TABLE 2 Composition of Artificial Brine SamplesSample mg/LNo. 1 2 3 4F 3.03 19
45、.4 20.5 4.09Na 9 500 65 000 31 000 75 000K 300 1 400 2 000 5 000Ca 550 1 000 700 2 000Mg 1 200 1 200 500 250Ba 30 650 300 300Cl 19 000 107 000 52 000 121 000D 3868 043SUMMARY OF CHANGESCommittee D19 has identified the location of selected changes to this standard since the last issue (D 3868 95 (199
46、9) that may impact the use of this standard.(1) D 5847 was added to 2.1.(2) A new Note 1 was added.(3) Section 8.2 was modified to use Type 1 water.(4) Section 13.4 was added.(5) Section 13 was added.ASTM International takes no position respecting the validity of any patent rights asserted in connec
47、tion with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsib
48、le technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful con
49、sideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.o
