1、Designation: D7614 12Standard Test Method forDetermination of Total Suspended Particulate (TSP)Hexavalent Chromium in Ambient Air Analyzed by IonChromatography (IC) and SpectrophotometricMeasurements1This standard is issued under the fixed designation D7614; the number immediately following the desi
2、gnation indicates the year oforiginal adoption or, in the case of revision, the 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 specifies a p
3、rocedure for the samplingand analysis of airborne particulate matter for hexavalentchromium in ambient air samples.1.2 The method involves drawing 21.6 m3ambient air (at 15L/min for 24 hours) through a sodium bicarbonate celluloseacid washed filter. Atmospheric hexavalent chromium is stabi-lized on
4、the alkaline coated filter.1.3 This method uses ion chromatography with post-columnderivatization with 1,5-diphenylcarbazide (DPC) and aUltraviolet/Visible (UV/VIS) detector.1.4 This method is applicable to the determination ofmasses of 0.10 to 20.0 ng of hexavalent chromium per samplewithout diluti
5、on.1.5 This method is applicable for hexavalent chromiummeasurement in the atmosphere from 0.004 ng/m3to 0.926ng/m3assuming a 21.6 m3sample volume. The range can beincreased using appropriate dilutions.1.6 Interconversion of trivalent and hexavalent chromiumduring sampling is minimized to the extent
6、 possible by usingthese sampling procedures.1.7 The corresponding method for workplace air samples isASTM Test Method D6832.1.8 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.9 This standard does not purport to address all of
7、 thesafety concerns, if any, 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:2D4840 Guide for Sample C
8、hain-of-Custody ProceduresD1193 Specification for Reagent WaterD1356 Terminology Relating to Sampling and Analysis ofAtmospheresD1357 Practice for Planning the Sampling of the AmbientAtmosphereD3195 Practice for Rotameter CalibrationD3586 Test Method for Chromium in Workplace Atmo-spheres (Colorimet
9、ric Method)3D5281 Test Method for Collection and Analysis of Hexava-lent Chromium in Ambient AtmospheresD6832 Test Method for the Determination of HexavalentChromium in Workplace Air by Ion Chromatography andSpectrophotometric Measurement Using 1,5-diphenylcarbazide3. Terminology3.1 DefinitionsFor d
10、efinitions of terms used in this testmethod, refer to Terminology D1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 eluentthe mobile phase used to transport the samplethrough the ion exchange column.3.2.2 resolutionthe ability of a column to separate con-stituents under specified test c
11、onditions.1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.03 on AmbientAtmospheres and Source Emissions.Current edition approved April 1, 2012. Published May 2012. DOI:10.1520/D7614-12.2For referenced ASTM standards
12、, 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.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho
13、cken, PA 19428-2959, United States.4. Summary of Test Method (1, 2, 3, 4)44.1 A known volume of air is drawn through a sodiumbicarbonate coated cellulose filter at a rate of 9.0 to 16.0 L/minfor 24 hours.4.2 After sampling, the chain-of-custody forms are appro-priately labeled and the filters are pl
14、aced in a cooler with ice forshipment to the laboratory. Upon receipt, the filters are placedin a freezer before preparation for analysis.4.3 The filters are extracted in sodium bicarbonate by meansof sonication for one hour. The extract is analyzed by ionchromatography using a system comprised of a
15、 guard column,an analytical column, a post-column derivatization module,and a UV/VIS detector. In the analysis procedure, hexavalentchromium exists as chromate due to the near neutral pH of theeluent. After separation through the column, the hexavalentchromium forms a complex with the 1,5-diphenylca
16、rbazide(DPC) which can be detected at 530 nm.4.4 One blank filter, per 10 samples prepared, is alsodesorbed and analyzed in accordance with 4.3.4.5 Hexavalent chromium is identified and quantified bycomparing its retention time and peak area to the correspond-ing standard solutions.5. Significance a
17、nd Use5.1 Hexavalent chromium is anthropogenic from a numberof commercial and industrial sources. It readily penetratesbiological membranes and has been identified as an industrialtoxic and cancer-causing substance. Hexavalent chromium is aknown inhalation irritant and associated with respiratory ca
18、n-cer (4).5.2 Ambient concentrations of hexavalent chromium arewell below detection limits of standard sampling methods,including Test Methods D3586 and D5281 (9).5.3 Ambient atmospheric concentrations of hexavalentchromium provides a means of evaluating exposures in amanner that can be related to h
19、ealth-based risk levels. Collect-ing actual monitoring data provides improved basis for healthassessments of potential exposures (2).5.4 This test method provides step-by-step instructions forsampling and analysis of hexavalent chromium collected onsodium bicarbonate coated cellulose filters exposed
20、 to ambientair.6. Interferences6.1 Sodium carbonate, if used as the stabilizing medium forthe hexavalent chromium filters, was observed to cause inter-ferences with the analysis (4).6.2 Higher concentrations of the sodium bicarbonate im-pregnating solution may cause flow restrictions during ambienta
21、ir sampling (4).6.3 The use of an impregnated filter of smaller pore size hasbeen shown to cause definite flow restrictions during ambientair sampling.6.4 Several types of filters have been determined to containtrace amounts of chromium which will leach out with time. Avariety of filters including p
22、olyvinyl chloride (PVC), Quartz,and mixed cellulose esters (MCE) were found to have highconcentrations of chromium and can not be used for low levelambient methods. Cellulose filters can be acid washed andalkali treated in order to stabilize and retain the hexavalentchromium following method specifi
23、cations (4).7. Apparatus7.1 Sampling System, capable of accurately and preciselysampling 9.0 to 16.0 L/min.NOTE 1An example of a sampling system for ambient air consists ofa filter inlet, a flow meter, a vacuum gage/pump, a timer and a powersupply as shown in Fig. 1. In operation, ambient air is dra
24、wn through thefilter assembly with a vacuum pump at a fixed flow rate between 9 to 16L/min.7.1.1 Sampling pumps, with an adjustable flow rate capableof maintaining a flow rate between 9.0 and 16.0 L/min througha sampling period of up to 24 hours. Sampling pump flow ratesshall be calibrated before sa
25、mpling begins. (See PracticeD3195.)7.1.2 Polytetrafluoroethylene (PTFE) filter holder, neededfor some sampling systems. All sampling systems shall havePTFE screens in order to minimize the potential of hexavalentchromium contamination.7.1.3 Filters, 47 mm ashless, cellulose filters. These filtersmus
26、t be acid washed before use to remove any residualchromium.NOTE 2Finding filters that are free of Chromium can be challengingbecause of the low detections determined when following this method.Cellulose filters can be acid washed and sodium bicarbonate treated inorder to stabilize the hexavalent chr
27、omium following method specifica-tions (4).7.1.4 Sample pump:4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.FIG. 1 Hexavalent Chromium Sampling System in Ambient AirD7614 1227.1.5 Glass funnel assembly, for use with the PTFE filterholders used with Samp
28、ling System Type A. These funnels areused to protect the filters from precipitation.7.1.6 Flow control device, capable of controlling and mea-suring selected volumetric flow rates to within 62 %. Rotame-ter control devices should be calibrated against a primarystandard (that is, a flowmeter whose ac
29、curacy is traceable to aprimary standard. (See Practice D3195.)7.1.7 Elapsed timer, to be placed in line with the samplepump to assist in detection of electrical interruptions that couldoccur over the 24 hour time interval.7.1.8 Freezer, for storage of filters before and after sam-pling. Freezer tem
30、peratures must be maintained below -18C.7.1.9 Ice cooler, for transport of filters to and from thesampling site.7.1.10 Flexible tubing, for use with flow calibration (see10.1.4).7.1.11 Calibration system, soap bubble, rotameter or massflow calibration system to calibrate flow meters (see 10.1).7.2 A
31、nalytical System:7.2.1 Ion chromatograph shall have the following compo-nents:7.2.1.1 Pump, capable of delivering a constant flow of in therange of 1 to 5 mL/min (millimetre/minute) at a pressure of 15to 150 MPa.7.2.1.2 Guard column, placed before the separator columnto remove particulate contaminan
32、ts and highly adsorptivecompounds from samples, prolonging analytical column life.7.2.1.3 Separator column, packed with a high capacity, highefficiency, hydrophobic, anion exchange column7.2.1.4 Post column reagent module, capable of delivering 0to 2 mL/min of reagent against a backpressure of up to
33、 40 kPa.7.2.1.5 Reaction coil, capable of mixing two flowingstreams with minimal band spreading.7.2.1.6 UV/VIS detector, low volume, flow through visibleabsorbance detector with a nonmetallic 1-cm flow path. Thedetection wavelength for hexavalent chromium is 530 nm.7.2.1.7 Injection valve, to ensure
34、 compatibility with aque-ous and reverse-phase eluents and protect sensitive samplesfrom metallic contamination. Sample loops of up to 1 mL willprovide enhanced detection limits.7.2.1.8 Autosampler (optional), to provide consistent opera-tion with precise quality assurance.7.2.1.9 Acquisition softwa
35、re, where the instrument is con-trolled and data are collected and processed using the instru-ment chromatography software and computer.7.3 Fully adjustable, air-displacement pipets, for small-volume dispensing of aqueous fluids of moderate viscosity anddensity. Pipets should comply with ISO 648, fo
36、r laboratoryglassware/pipettes.7.4 Glassware, made of borosilicate glass, which shouldcomply with ISO 3585 for borosilicate glass.7.4.1 Volumetric flasks, 100 mL, 200 mL, 1 L, and 2 L,which should comply with ISO 1042 for laboratory glassware/one-mark volumetric flasks.7.5 Analytical balance, to pro
37、vide reliable performance andaccurate readability to 0.001 mg.7.6 Centrifuge tubes with caps, 14 mL disposable polysty-rene round bottom tubes with snap caps for sample preparation.7.7 Petri dishes, 47 millimetre (mm) disposable plastic unitsto be used in the storage of the acid washed, sodium bicar
38、bon-ate coated filters.7.8 Nitrogen purged Glove box (2), one box to be use toprepare the filters before sampling. The second box should beused to prepare the filters for analysis. The boxes should besealed airtight with a double-layered closed gasket system andcontain suspended plastic coated scree
39、ns to hold filters duringpreparation. The boxes should be purged with ultra-purenitrogen.7.9 Ultrasonicator, to be used for standard preparation.7.10 Disposable gloves, for sample handling and preventionof sample contamination.8. Reagents8.1 For the analysis of low level hexavalent chromium, onlyuse
40、 reagents of the highest recognized analytical grade andwater as specified in (see 8.1.1).8.1.1 Water, complying with the requirements of ASTMType I deionized water (DI water) as specified in SpecificationD1193 (18 MV-cm).8.1.2 Ammonium sulfate (NH4)SO4, 99.999 % purity basedon trace metals, specifi
41、c gravity 1.77 (g/mL).8.1.3 Ammonium hydroxide (NH4)OH, reagent grade,28.030.0 % NH4basis, specific gravity 0.99 (g/cm3).8.1.4 1,5-diphenylcarbazide (C13N4O), ACS crystalline(DPC).8.1.5 Methanol (CH3OH), HPLC grade, 0.2 micron filtered,greater than 99.9 % purity, 0.79 (g/cm3).8.1.6 Sulfuric acid (H2
42、SO4), concentrated, 99.999 % puritybased on trace metals, specific gravity 1.84 (g/mL).8.1.7 Sodium bicarbonate (NaHCO3), greater than 99.5 %purity.8.1.8 Potassium dichromate (K2Cr2O7), 99.99+ % puritybased on trace metals, crystalline. Before use it should be driedat 105C for 1 hour then cooled in
43、a dessicator. See 8.1.12.1 forinstructions on preparing standard solutions.8.1.9 Sodium Bicarbonate Extraction Solution (20 mM),dissolve 3.36 grams (g) of sodium bicarbonate (see 8.1.7)inDIwater (see 8.1.1) in a 2.0 L volumetric flask. Mix well anddilute to mark. Stopper and mix thoroughly.8.1.10 El
44、uent Stock, 250 mM ammonium sulfate (see 8.1.2)and 100 mM ammonium hydroxide (see 8.1.3): dissolve 66 gof ammonium sulfate in 1000 mL DI water (see 8.1.1)ina2L volumetric flask. Add 7 mL of ammonium hydroxide anddilute to volume with DI water. Stopper and mix thoroughly.8.1.11 Post-Column Derivatizi
45、ng Reagent (PCR),ina50mL volumetric flask, dissolve 0.25 gm of 1,5-diphenylcarbazide (see 8.1.4) in 50 mL of HPLC-grade metha-nol (see 8.1.5). Sonicate until DPC goes into solution. In a 500mL volumentric flask add approximately 300 mL of DI water(see 8.1.1). Carefully add 14 mL of 99.999 % sulfuric
46、 acid (see8.1.6) to the DI water, allow to cool after mixing. AddDPC-methanol solution to sulfuric acid solution. Dilute to 500mL with DI water, stopper and mix thoroughly. This reagent isstable for four or five days. To minimize waste, it should beprepared in 500 mL quantities as needed.D7614 1238.
47、1.12 Hexavalent Chromium Standard Solutions :8.1.12.1 Hexavalent Chromium Stock Standard Solution(1000 g/mL Cr6+), stock hexavalent chromium standardsare available commercially or can be prepared by diluting0.283 grams of potassium dichromate (see 8.1.8) with DI water(see 8.1.1) in a 100 mL volumetr
48、ic flask. Dilute to volume with20 mM sodium bicarbonate extraction solution, stopper andmix thoroughly.NOTE 3Potassium chromate (K2CrO4) can be used as an alternative topotassium dichromate for the preparation of the hexavalent chromiumstock standard solution.NOTE 4Two primary stock solutions should
49、 be prepared and/orobtained from separate sources. One is to be used exclusively for thecalibration standards and the other for the laboratory control samples(LCS) and calibration verification.8.1.12.2 Hexavalent Chromium Working Standard Solution,to be prepared in the 20 mM sodium bicarbonate extractionsolution. The working standard solution is at 1000 ng/mL.Dilute 100 L of the stock standard solution (see 8.1.12.1) withextraction solution (see 8.1.9) in a 100 mL volumetric flask.Dilute to volume, stopper and mix thoroughly. The workingstandard solution is stable for
