1、Designation: D3868 15Standard Test Method forFluoride Ions in Brackish Water, Seawater, and Brines1This standard is issued under the fixed designation D3868; 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 () 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 selec
3、tive electrode.1.2 Samples containing from 1.0 to 25 mg/L can be ana-lyzed by this test method.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any,
4、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.2. Referenced Documents2.1 ASTM Standards:3D1129 Terminology Relating to WaterD1193 Specificatio
5、n for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3. Terminology3.1 D
6、efinitionsFor definitions of terms used in this testmethod, refer to Terminology D1129.4. Summary of Test Method4.1 A fluoride selective electrode, reference electrode, andmillivoltmeter are used to determine fluoride in brine samplesby a standard addition method.4.2 The fluoride selective electrode
7、 consists of a lanthanumfluoride crystal that develops an electrode potential corre-sponding to the level of fluoride ion 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
8、 results are used to evaluate theorigin of the water, determine if it is a possible pollutant, or ifit is related to a potential source of a valuable mineral. Forexample, in geochemical studies some correlation data indicatethat fluoride is an indirect indicator of the presence of lithium.6. Interfe
9、rences6.1 Metal ions such as aluminum and iron (III) interferewith the fluoride determination by forming complexes withfluoride ions. The buffer solution contains a complexing agentthat preferentially complexes these metal ions. This solutionalso contains a pH buffer to reduce electrode interference
10、 fromhydroxide ions and to prevent the formation of HF. Sodiumchloride is added as ionic strength adjustor. Increasing amountsof 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. Apparat
11、us7.1 Millivoltmeter accurate to 60.1 mV), specific ion meter.NOTE 1A specific ion meter that directly reads concentration may beused.7.2 Fluoride Selective Electrode, reference electrode.7.3 Microlitre Pipets.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless
12、 otherwise indicated, it is intended thatall reagents shall conform to the specification of the Committeeon Analytical Reagents of the American Chemical Society,1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of D19.05 on Inorganic Constitue
13、nts in Water.Current edition approved March 15, 2015. Published April 2015. Originallyapproved in 1979. Last previous edition approved in 2009 as D3868 09. DOI:10.1520/D3868-15.2Additional information is contained in the following references: Hoke, S. H.,Fletcher, G. E., and Collins, A. G., “Fluorid
14、e and Iodide Selective ElectrodesApplied to Oilfield Brine Analysis,” U.S. Department of Energy, Report ofInvestigations, BETC/RI-78/7.Rix, C. J., Bond, A. M., and Smith, J. D., “DistrictDetermination of Fluoride in Sea Water with a Fluoride Selective Ion Electrode bya Method of Standard Additions,”
15、 Analytical Chemistry, Vol 48, 1976, p. 1236.3For 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 onthe ASTM website.*A Summary of Ch
16、anges section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently hig
17、h purity to permit its use without lessening theaccuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean reagent water conformingto Specification D1193, Type I. Other reagent water types maybe used provided it is first ascertained tha
18、t the water is ofsufficiently high purity to permit its use without adverselyaffecting the precision and bias of the test 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 di
19、nitrilo tetraacetic acid),and 57 mL of glacial acetic acid in 500 mL of water. Slowlyadd NaOH solution (200 g/L) to adjust 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 (
20、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 contain 2000 mg ofF/L. Alternatively, certified fluoride stock solutions are com-mercially available through chemical supply vendors and maybe used.9. Sampling9.1 Collect the sample
21、 in accordance with Practices D3370.10. 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 solution. Place electrodes in the solutionto a depth of
22、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 theabove step for the second addition.11. Calculation11.1 Calcul
23、ate the slope of the electrode as follows:Slope 5EB2 EAlogB# 2 logA#(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 the electrode should meet the manufacturersspecifications
24、.11.2 Calculate the concentration of fluoride in the sample asfollows:2A 5 mg/L 5XfantilogSEslopeD2 131000 (2)where:X = change in concentration upon addition of standard(mg Fadded per 80 mL of solution),f = dilution factor (80 mL/mL of sample), andE = change in potential resulting from addition ofst
25、andard.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 0.08X10.73 (3)Sc5 0.063X10.097where:ST= overall precision,So= single-operator precision,
26、 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 estimates are based on aninterlaboratory study on four artificial brine
27、 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. Practice D2777was used in developing these precision and bias estimat
28、es.12.3 Precision and bias for this test method conforms toPractice D2777 77, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofPractice D2777 13, these precision and bias data do meetexisting requirements for interlaboratory studies of CommitteeD19 test meth
29、ods.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.4Reagent Chemicals, American Chemical Society Specifications,
30、 AmericanChemical Society, Washington, DC. 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
31、. (USPC), Rockville,MD.5Also available as TISAB II from Orion Research Inc.6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D19-1060. ContactASTM CustomerService at serviceastm.org.TABLE 1 Determination of Precision and BiasAmoun
32、t 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 + 14.2D3868 15213.2 Calibration and Calibration Verification:13.2.1 Determine the slope of the electrode. The slopeshould meet the manufacturers speci
33、fications.13.2.2 Verify the electrode by analyzing a sample at theconcentration near the mid-range should fall within 615%ofthe known concentration.13.2.3 If calibration cannot be verified, recalibrate theinstrument.13.2.4 It is recommended to analyze a blank and continuingcalibration verification (
34、CCV) at a 10 % frequency. The resultsshould fall within the expected precision of the method or 615% of the known concentration.13.3 Initial Demonstration of Laboratory Capability:13.3.1 If a laboratory has not performed the test before, or ifthere has been a major change in the measurement system,
35、forexample, new analyst, new instrument, and so forth, a precisionand bias study must be performed to demonstrate laboratorycapability.13.3.2 Analyze seven replicates of a standard solutionprepared from an Independent Reference Material containing amid-range concentration of fluoride. The matrix and
36、 chemistryof the solution should be equivalent to the solution used in thecollaborative study. Each replicate must be taken through thecomplete analytical test method including any sample preser-vation and pretreatment steps.13.3.3 Calculate the mean and standard deviation of theseven values and com
37、pare to the acceptable ranges of bias inTable 1. This study should be repeated until the recoveries arewithin the limits given in Table 1. If a concentration other thanthe recommended concentration is used, refer to PracticeD5847 for information on applying the F test and t test inevaluating the acc
38、eptability of the mean and standard devia-tion.13.4 Laboratory Control Sample (LCS):13.4.1 To ensure that the test method is in control, prepareand analyze a LCS containing a mid-range concentration offluoride with each batch (laboratory-defined or twentysamples). The laboratory control samples for
39、a large batchshould cover the analytical range when possible. It isrecommended, but not required to use a second source, ifpossible and practical for the LCS. The LCS must be takenthrough all of the steps of the analytical method includingsample preservation and pretreatment. The result obtained for
40、the LCS shall fall within 615 % of the known 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 results mustbe qualified with an indication that they do not fall
41、 within theperformance criteria of the test method.13.5 Method Blank:13.5.1 Analyze a reagent water test blank with eachlaboratory-defined batch. The concentration of fluoride foundin the blank should be less than 1.0 mg/L. If the concentrationof fluoride is found above this level, analysis of sampl
42、es ishalted until the contamination is eliminated, and a blank showsno contamination at or above this level, or the results must bequalified with an indication that they do not fall within theperformance criteria of the test method.13.6 Matrix Spike (MS):13.6.1 Fluoride is not an analyte that can be
43、 feasibly spikedinto samples.13.7 Duplicate:13.7.1 To check the precision of sample analyses, analyze asample in duplicate with each laboratory-defined batch. If theconcentration of the analyte is less than five times the detectionlimit for the analyte, a matrix spike duplicate (MSD) should beused.1
44、3.7.2 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 Practice D5847 for informa-tion on applying the F test.13.7.3 If the result exceeds the precision limit, the batchmust be reanalyzed or the results
45、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) submitted as a regular sam
46、ple (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; electrode; fluorideTABLE 2
47、Composition of Artificial Brine SamplesSample mg/LNo. 1 2 3 4F 3.03 19.4 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 000D3868 153SUMMARY OF CHANGESCommittee D19 has identified the location of s
48、elected changes to this standard since the last issue(D3868 09) that may impact the use of this standard. (Approved March 15, 2015.)(1) Revised 13.2.4 and 13.4.1.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this st
49、andard. 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 responsible 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 co
