1、Designation: D4765 13Standard Test Method forMeasurement of Fluorides in Workplace Atmospheres byIon-Selective Electrodes1This standard is issued under the fixed designation D4765; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the simultaneous collection andseparate measurements of gaseous fluoride (for exampl
3、e,hydrogen fluoride) and particulate fluoride found in certainindustrial workplaces. The gaseous fluorides and particulatefluorides collected are reported in terms of fluoride. Themethod covers sample collection, preparation, and fluoridemeasurement.1.2 The procedure is not applicable to the collect
4、ion oranalysis of gaseous fluoro compounds (for example, fluorocar-bon or fluorosulfur compounds).1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
5、he 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:2D1193 Specification for Reagent WaterD1356 Terminology Relating to Sampling and Analysis ofAtmospheresD484
6、0 Guide for Sample Chain-of-Custody ProceduresD5337 Practice for Flow Rate Adjustment of Personal Sam-pling PumpsE1370 Guide for Air Sampling Strategies for Worker andWorkplace Protection3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D1356.4. Summ
7、ary of Test Method4.1 Particulate material from a measured volume of air iscollected by means of a membrane filter. Gaseous fluoride,from the sample of air, is absorbed by an alkali-impregnatedcellulose pad placed behind the membrane filter. The mem-brane filter and collected solids are made alkalin
8、e, ashed, andthe residue fused with additional alkali. Finally, the fluoride isdetermined in a solution of the melt by use of a fluorideion-selective electrode. Gaseous fluoride is determined in anaqueous extract of the cellulose pad, also by means of thefluoride ion-selective electrode.5. Significa
9、nce and Use5.1 The capability of this test method to collect and quan-titate both particulate and gaseous fluorides over the rangesnormally encountered in industrial atmospheres makes it ap-plicable for industrial hygiene evaluation and control purposes.The recommended range of this test method is f
10、rom 0.005 to 5mg F/m3air.6. Interferences6.1 Because an ion-selective electrode responds to ionicactivity, insoluble and complex forms of fluoride must bereleased by appropriate combinations of fusion, adjustment ofpH, and addition of complexing agents.6.2 Filter MaterialsNot all filter materials ca
11、n be usedeffectively for sampling particulate fluorides in workplace air.Cellulosic membrane filters are the most suitable filter types forsampling of fluorides. Several manufacturers offer mixed-cellulose ester filters commercially; nevertheless it is essentialto check the quality of each filter ba
12、tch used for sampling.6.3 Acidity (pH) and ionic strengths of fluoride standardsolutions must be matched to those of samples.6.4 Temperature of sample and standard solutions must becontrolled within 62C.7. Apparatus7.1 Personal Sampling Pump, capable of maintaining con-stant air flow (65 %) in the r
13、ange 15 L/min through a filterholder (7.2) containing a 0.8-m pore size cellulosic membranefilter (7.3) and cellulose pad (7.4) for a period of up to 8 hours.1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.04 on Wor
14、kplace AirQuality.Current edition approved April 1, 2013. Published April 2013. Originallyapproved in 1988. Last previous edition approved in 2008 as D4765 03(2008).DOI: 10.1520/D4765-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at servicea
15、stm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17.2 Filter HolderFor sampling of inhalable fraction ofaeroso
16、ls, of suitable diameter for the filters (for example,37-mm; see 7.3). The holder shall be numbered for identifica-tion.7.3 Membrane Filter, of mixed-cellulose esters (MCE),0.8-m pore size, and of diameter to fit the filter holder (see7.2).7.4 Cellulose Pad, of size to fit the filter holder (see 7.2
17、).The pad is commercially available as a plain, unimpregnatedpad or impregnated with alkali (8.3).7.5 Crucibles, 20-mL, nickel, platinum, or suitable alloys ofnickel and chromium.7.6 Fluoride Ion-Selective Electrode.7.7 Reference Electrode, calomel type, preferably combinedwith the fluoride ion-sele
18、ctive electrode.7.8 Electrometer or Expanded Scale pH Meter, with amillivolt scale for measurement of potentials.NOTE 1Commercial potentiometers for fluoride sensitive electrodesare equipped with internal calibration modes.7.9 Magnetic Stirring Bar, fluorocarbon-coated.7.10 Plastic Beakers, 50 and 1
19、00-mL capacities.7.11 Beakers, borosilicate glass, 250-mL capacity.7.12 Volumetric Flasks, 50 and 100-mL capacity.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 specifications of the
20、 Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.38.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean Type I Reagent Waterconforming to Specification D1193.8.3 Alkaline Fixative SolutionDissolve 25 g
21、 of sodiumcarbonate (Na2CO3) in water, add 20 mLglycerol, and dilute to1 L with water.8.4 Buffer SolutionDissolve 60 g of citric acid monohy-drate (C2H8O7H2O), 210 g of sodium citrate(Na3C6H5O72H2O) and 53.5 g of ammonium chloride(NH4Cl) in 500 mLwater.Add 67 mLof ammonium hydroxide(NH4OH) (sp gr =
22、0.90) and dilute to 1 L with water.8.5 Fluoride Solution, Standard (100 g/mL)Dissolve0.2211 g sodium fluoride (NaF, dried at 105C for 2 h) in waterand dilute to volume in a 1-L volumetric flask.8.6 Ethanol, analytical grade.8.7 Borate-Carbonate Fusion MixtureThoroughly mix a1+2 (w/w) combination of
23、sodium tetraborate (Na2B4O7) andsodium carbonate (Na2CO3).8.8 Hydrochloric Acid (1+1)Mix one part hydrochloricacid to one part water (8.2) as a homogeneous solution.9. Sampling9.1 Cellulose Pad ImpregnationMoisten the cellulose pad(7.4) with a measured volume of alkaline fixative solution (see8.3);
24、0.8 mL is required for a pad of 37-mm diameter. Dry thepad at 105C for 30 to 45 min, or allow to dry overnight atroom temperature in a dessicator.NOTE 2Preparation of alkali-impregnated pads must be carried out ina low-fluoride environment with minimum potential for contamination.9.2 Sampler Assembl
25、yAssemble the filter holder, insertingan impregnated pad with membrane filter atop it, and seal theassembly against air leakage. Close the inlet and outletopenings of the filter holder.9.3 Personal Sampling PumpUse personal samplingpumps at their design flow rate (1-5 L/min) and calibrated inaccorda
26、nce with Practice D5337.9.4 Sample CollectionFor general information on sam-pling strategies, refer to Guide E1370.9.4.1 Equip the worker whose exposure is to be evaluatedwith a sampler (9.2) connected by a ca. 75-cm length offlexible tubing to a belt-supported personal sampling pump(9.3). Attach th
27、e sampler to place it within the workerspersonal breathing zone for sampling. Draw air through thesampler at a calibrated rate of 1-5 L/min; a sampling rate of 2L/min is common. On termination of sampling, record theduration of sampling. Obtain a minimum air sample of 250 L.9.5 Sample TransportTrans
28、port the samplers to the labo-ratory so as to prevent contamination or damage. Followchain-of-custody procedures to document sample traceabilityin accordance with Guide D4840.10. Analysis10.1 Fluoride Calibration Standards:NOTE 3These standards may be stored for several months in tightlycapped polye
29、thylene bottles, under refrigeration.10.1.1 Particulate FluorideAdd 1.0 g borate-carbonatefusion mixture to each of four 250-mL beakers containing 10mL of water and 50 mL of buffer solution (8.4). Add a fewdrops of (1 + 1) hydrochloric acid (see 8.8) and add varioussize aliquots (1, 5, 10, and 25 mL
30、) of 100 g/mL standardfluoride solution (see 8.5) to produce a series of workingstandards (1, 5, 10, and 25 g/F/mL). Transfer to a 100-mLvolumetric flask, and dilute to volume with water.10.1.2 Gaseous FluorideInto each of four 100-mL volu-metric flasks, place 10 mL of water and 50 mL of buffersolut
31、ion (see 8.4). Add various size aliquots (1, 5, 10, and 25mL) of 100 g/mL standard fluoride solution (see 8.5) toproduce a series of working standards (1, 5, 10, and 25 gF/mL). Dilute to volume with water.10.2 Calibration:3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical
32、 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. Pharmacopeial Convention, Inc. (USPC), Rockvill
33、e,MD.D4765 13210.2.1 For calibration of the electrode, pour about 20 mL ofthe working standard solution into a plastic beaker containinga fluorocarbon-coated stirring bar (7.9). Adjust solution towithin 62C of a selected standard temperature, for example,25C. Insert the fluoride and reference electr
34、odes into theconstantly stirred solution and measure the potential after twominutes. Repeat for each of the working standards (10.1).10.2.2 Prepare a calibration graph, on semilog scale, relat-ing potential, in mV (linear scale), to concentration of fluoridein m/mL (log scale). Reproducibility of ea
35、ch point should be61 mV. A linear calibration graph is obtained in the 0.5 to 25g/mL range, with a slope of between 57 and 59 mV pertenfold change in fluoride concentration.10.2.3 Prepare separate calibration graphs for particulateand gaseous fluoride from potential measurements of thesestandards (s
36、ee 10.1). If solutions containing less than 0.5g/mL are measured, additional standards must be preparedsince the calibration graph might not be linear at low fluorideconcentrations.10.3 Sample Preparation and Measurement Procedure:10.3.1 Particulate FluorideCarefully remove the mem-brane filter from
37、 the filter holder and place it in a nickel,Inconel, or platinum crucible containing 0.5 g borate-carbonatefusion mixture. Transfer any dust from inside the filter coverand retaining ring to the crucible. Drench the filter with ethanoland ignite with a small gas flame. Heat the residue to fusiontemp
38、erature (as evidenced by a dull, red glow until all of thesample is consumed) for 1 to 2 min. During the fusionprocedure, do not overheat crucible, as fluoride can be lost dueto volatilization. Cool to room temperature and dissolve thecrucible contents in a few mL of water. Transfer the samesolution
39、 into a plastic beaker by means of 25 mL of buffersolution (see 8.4) followed by a rinse of the crucible with a fewdrops of (1+1) hydrochloric acid (see 8.8). Dilute to 50 mL ina volumetric flask, mix and bring to standard temperature, forexample, 25C. Pour about 20 mL of the solution into a plastic
40、beaker and measure the potential while the electrodes areimmersed in the gently stirred solution. Convert potential (mV)to fluoride concentration (g/mL) by means of the calibrationgraph determined from the standard fluoride series containingborate-carbonate flux (see 10.2).10.4 Gaseous FluorideTrans
41、fer the impregnated cellulosepad to a 100-mL plastic beaker containing 25 mL water and 25mLbuffer solution (see 8.4).Allow the pad to soak for about 30min with sufficient stirring to reduce it to a pulp. Bring thesolution to standard temperature (for example, 25C), insert theelectrodes, and measure
42、the potential of the gently stirredmixture after 2 min. Convert potential (mV) to fluorideconcentration (g/mL) by means of the calibration graphdetermined from the standard fluoride series (see 10.2).11. Calculations11.1 The concentration of particulate fluorides in air, inte-grated over the samplin
43、g period, is calculated as follows:Cp5 0.05 3C1V(1)where:Cp= concentration of particulate fluoride, in mg/m3,0.05 = conversion factor for a 50-mL sample volume andthe conversion of micrograms to milligrams,C1= concentration of fluoride in particulate sample solu-tion in g/mL, andV = volume of air sa
44、mple in m3, corrected to 25C and 1atm.11.2 The concentration of gaseous fluoride in air, integratedover the sampling period, is calculated as follows:Cg5 0.05 3C2V(2)where:Cg= concentration of gaseous fluoride in mg/m3,0.05 = conversion factor for a 50-mLsample voume and theconversion of micrograms
45、to milligrams,C2= concentration of fluoride in gaseous sample solutionin g/mL,V = volume of air sample in m3, corrected to 25C and 1atm.11.3 If desired, gaseous fluoride concentration in air, inmg/m3, may be converted to equivalent concentration ex-pressed as parts per million as follows:Cg, mg/m331
46、.29 5 Cg, ppm (3)12. Precision and Bias12.1 PrecisionRepeatability (Both single-analyst andoverall):12.1.1 Four levels of gaseous fluoride were generated andcollected on a treated filter: 0.030, 0.295, 1.49, and 2.90 mgfluoride/sample. Each concentration was analyzed in triplicateby eight participat
47、ing laboratories. The single operator relativestandard deviation (RSD) varied from 10.3 % to 2.8 % with apooled relative standard deviation of 7.5 %. The overallrelative standard deviation for the eight laboratories variedfrom 24.8 % to 7.6 % with a pooled relative standard deviationof 16.0 %.412.1.
48、2 To prepare performance evaluation samples, threelevels of particulate fluoride were produced by weighing astandard sample and placing sample aliquots onto filters atlevels of 0.742, 1.48, and 2.41 mg fluoride/sample. Eachloading level was analyzed in triplicate by eight participatinglaboratories.
49、The single operator relative standard deviation(RSD) varied from 13.9 % to 4.4 % with a pooled relativestandard deviation of 9.2 %. The overall relative standarddeviation for the eight laboratories varied from 31.5 % to21.2 % with a pooled relative standard deviation of 27.2 %.412.2 Bias:12.2.1 Particulate StandardsRecoveries of knownamounts of standard particulate fluoride are shown in Table 1.The overall percent recovery of the particulate fluoride samplewas 78.2 % over a concentration range from 0.74 to 2.41 mg offluoride per
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