1、Designation: D 5085 02Standard Test Method forDetermination of Chloride, Nitrate, and Sulfate inAtmospheric Wet Deposition by Chemically Suppressed IonChromatography1This standard is issued under the fixed designation D 5085; the number immediately following the designation indicates the year oforig
2、inal adoption or, in the case of revision, the year of last revision. 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 is applicable to the determination ofchloride
3、, nitrate, and sulfate in atmospheric wet deposition(rain, snow, sleet, and hail) by chemically suppressed ionchromatography (1)2. For additional applications refer to TestMethod D 4327.1.2 The concentration ranges for this test method are listedbelow. The range tested was confirmed using the interl
4、abora-tory collaborative test (see Table 1 for statistical summary ofthe collaborative test).MDL (mg/L) (2)Range ofMethod(mg/L)RangeTested(mg/L)Chloride 0.03 0.092.0 0.151.36Nitrate 0.03 0.095.0 0.154.92Sulfate 0.03 0.098.0 0.156.521.3 The method detection limit (MDL) is based on singleoperator prec
5、ision (2) and may be higher or lower for otheroperators and laboratories. The precision and bias data pre-sented are insufficient to justify use at this low level, however,many workers have found that this test method is reliable atlower levels than those that were tested.1.4 This standard does not
6、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 practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are gi
7、ven in Section 9.2. Referenced Documents2.1 ASTM Standards:3D 883 Terminology Relating to PlasticsD 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 2777 Practice for Determination of Precision and Bias ofAppl
8、icable Methods of Committee D19 on WaterD 3670 Guide for Determination of Precision and Bias ofMethods of Committee D-22D 4210 Practice for Interlaboratory Quality Control Proce-dures and a Discussion on Reporting Low-Level DataD 4327 Test Method for Anions in Water by ChemicallySuppressed Ion Chrom
9、atographyD 5012 Guide for Preparation of Materials Used for theCollection and Preservation of Atmospheric Wet Deposi-tionE 380 Practice for Use of the International System of Units(SI) (the Modernized Metric System)E 694 Specification for Laboratory Glass Volumetric Appa-ratus3. Terminology3.1 Defin
10、itionsFor definitions of terms used in this testmethod, refer toTerminologies D 883, D 1129, and D 1356 andTest Method D 4327 and Practice E 380.4. Summary of Test Method4.1 Ion chromatography combines conductometric detectionwith the separation capabilities of ion exchange resins. (1) Afiltered ali
11、quot of the sample, ranging in size from 50 to 250L, is pumped through an ion exchange column where theanions of interest are separated. Each ions affinity for theexchange sites, known as its selectivity quotient, is largelydetermined by its radius and valence. Because different ionshave different s
12、electivity quotients, the sample ions elute fromthe column as discrete bands. Each ion is identified by itsretention time within the exchange column. The sample ionsare selectively eluted off the separator column and onto asuppressor column, where the conductivity of the eluent ions isreduced and th
13、e sample ions are converted to their correspond-ing strong acids. The separated anions are detected by aconductance cell. The chromatograms produced are displayedon a strip chart recorder or other data acquisition device.1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality
14、 and is the direct responsibility of Subcommittee D22.03 on AmbientAtmospheres and Source Emissions.Current edition approved October 10, 2002. Published December 2002. Origi-nally published as D 5085 90. Last previous edition D 5085 95.2The boldface numbers in parentheses refer to references at the
15、end of this testmethod.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.1Copyright ASTM International, 100 Bar
16、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Measurement of peak height or area is used for quantitation.The ion chromatograph is calibrated with standard solutionscontaining known concentrations of the anion(s) of interest.Calibration curves are constructed from whic
17、h the concentra-tion of each analyte in the unknown sample is determined. Foradditional information on ion chromatography refer to TestMethod D 4327.5. Significance and Use5.1 This test method is useful for the determination of theanions: chloride, nitrate, and sulfate in atmospheric wet depo-sition
18、.5.2 Fig. X1.1 in the appendix represents cumulative fre-quency percentile concentration plots of chloride, nitrate, andsulfate obtained from analyses of over 5000 wet depositionsamples. These data may be used as an aid in the selection ofappropriate calibration solutions. (3)6. Interferences6.1 Unr
19、esolved peaks will result when the concentration ofone of the sample components is 10 to 20 times higher thananother component that appears in the chromatogram as anadjacent peak. Decreasing the eluent concentration or flow rate,increasing column length, or decreasing sample size maycorrect this pro
20、blem.6.2 Interferences may be caused by ions with retentiontimes that are similar to the anion of interest.The retention timeof sulfite may be similar to nitrate or sulfate. Other possibleinterfering ions are bromide and phosphate. Before analyzingprecipitation samples, measure the retention times o
21、f thesepossible interfering ions. Interference is common in some typesof wet deposition samples. If this interference is anticipated,decreasing the eluent concentration or flow rate, increasingcolumn length, or decreasing sample size will result in im-proved peak resolution.6.3 Water from the sample
22、 injection will cause a negativepeak (water dip) in the chromatogram when it elutes becauseits conductance is less than that of the suppressed eluent.Chloride may elute near the water dip and must be sufficientlyresolved from the dip to be accurately quantified. This can beachieved by changing the e
23、luent concentration or decreasingthe flow rate. The potential interference of the negative peakcan be eliminated by adding an equivalent of 100 l of aprepared eluent concentrate (solution that is 100 times moreconcentrated than the eluent used for analysis) per 10.0 mL ofsample. Identical eluent add
24、itions must also be included incalibration and quality control solutions.6.4 Decreases in retention times and resolution are symp-toms of column deterioration which may be caused by thebuildup of contaminants on the exchange resin. Refer to themanufacturers guidelines for instructions on cleaning th
25、ecolumn resin and column filter beds. Excising the contami-nated portion of the column and changing the filters may alsoimprove performance. If the procedure in this section do notrestore the retention times, replace the column.6.5 Contaminated valves and sample lines may also reducesystem performan
26、ce causing decreased retention times andresolutions. Refer to the manufacturers guidelines for instruc-tions on cleaning the valves and replacing the lines.NOTE 1Review operational details and refer to the trouble shootingguide in the Operators Manual to determine the cause of decreasedretention tim
27、es and resolution prior to extensive cleaning or changing ofall valves, columns, filters, sample lines, or all of the above.6.6 The presence of air bubbles in the columns, tubing, orconductivity detector cell may cause baseline fluctuations andpeak variability. Prevent introducing air into the syste
28、m wheninjecting samples and standards. The use of degassed water foreluents and regenerants may help to minimize the introductionof air (See 8.2).6.7 For more information on interferences refer to TestMethod D 4327.7. Apparatus7.1 Ion ChromatographSelect an instrument equippedwith an injection valve
29、, a sample loop, separator column(s),TABLE 1 Precision and Bias for Chloride, Nitrate, and Sulfate Determined from the Synthetic Atmospheric Wet Deposition SamplesUsed in the Interlaboratory Comparison StudyAnalyteAmountAdded,mg/LMeanRecovery,mg/LnAPrecision mg/LBias,mg/LSignificantBiasBStC95 %Repro
30、ducibilityLimitSoD95 %RepeatabilityLimitChloride 0.15 0.157 36 0.0535 0.150 0.0116 0.0325 0.007 no0.30 0.293 35 0.0554 0.155 0.0291 0.0815 0.007 no0.68 0.652 36 0.0549 0.154 0.0237 0.0664 0.028 biased low1.36 1.368 36 0.1 0.28 0.0431 0.121 0.008 noNitrate 0.15 0.138 24 0.0362 0.101 0.0289 0.0809 0.0
31、12 no1.08 1.077 24 0.0495 0.139 0.0421 0.118 0.003 no2.44 2.486 22 0.0197 0.0552 0.0183 0.0512 0.046 biased high4.92 4.999 24 0.126 0.353 0.075 0.21 0.079 biased highSulfate 0.15 0.172 36 0.055 0.154 0.0304 0.085 0.022 no1.43 1.442 35 0.0683 0.191 0.0369 0.103 0.012 no3.23 3.358 36 0.13 0.364 0.046
32、0.129 0.128 biased high6.52 6.775 36 0.37 1.04 0.109 0.305 0.255 biased highANumber of samples included in final statistical analysis after removal of outlier data.B95 % confidence level.CBetween laboratory precision, reproducibility.DWithin laboratory precision (pooled single operator precision), r
33、epeatability.D5085022suppressor column(s), pump(s), and detector meeting require-ments specified. Peripheral equipment includes compressedgas, a suitable data acquisition device such as a strip chartrecorder, an integrator, or computer, and may include anautomatic sampler.7.1.1 TubingTubing that com
34、es in contact with samplesand standards must be manufactured from inert material suchas polyethylene plastics or TFE-fluorocarbon.7.1.2 Anion Guard ColumnAlso called a precolumn, it isplaced before the separator column. The guard column con-tains the same resin as the separator column and is used to
35、protect it from being fouled by particulates or organic constitu-ents. Using an anion guard column will prolong the life of theseparator column.47.1.3 Anion Separator ColumnThis is a column packedwith a pellicular low-capacity anion exchange resin con-structed of polystyrene-divinylbenzene beads coa
36、ted with quar-tenary ammonium active sites.57.1.4 Anion Suppressor ColumnPlace following the sepa-rator column. This may be in the form of an anion micro-membrane suppressor or an anion self-regenerating suppressor.The first type of suppressor utilizes a semipermeable mem-brane containing anion exch
37、ange sites to suppress eluentconductance.6The second type of suppressor uses the neutral-ized cell effluent as the source of water for the regenerantchamber water.7.1.5 Compressed Gas (Nitrogen or Air)Use ultra-highpurity 99.999 % (v/v) compressed gas that is oil, particulate,and water free to actua
38、te the valves and to pressurize theregenerant flow system as needed.7.1.6 DetectorSelect a flow-through, temperature-compensated, electrical conductivity cell with a volume ofapproximately 6 L coupled with a meter capable of readingfrom 0 to 1000 s/cm on an analog or digital scale.7.1.7 PumpUse a pu
39、mp capable both of delivering aconstant flow rate of approximately 1 to 5 mL/min and oftolerating a pressure 1379 to 13 790 kPa. A constant pressure,constant flow pump is recommended for enhanced baselinestability.All interior pump surfaces that will be in contact withsamples and standards must be m
40、anufactured from inert,non-metallic materials.7.1.8 Data Acquisition System:7.1.8.1 RecorderThis must be compatible with the maxi-mum conductance detector output with a full-scale responsetime of 0.5 s or less. A two pen recorder with variable voltageinput settings is recommended.7.1.8.2 IntegratorI
41、f an integrating system is employed,the data acquisition unit must be compatible with the maximumdetector output to quantitate the peak height or area. If anintegrator is used, the maximum peak height or area measure-ment must be within the linear range of the integrator.7.1.9 Sample LoopSelect a sa
42、mple loop with a capacity of50 to 250 L.7.1.10 Sample Introduction SystemSelect one of the fol-lowing:7.1.10.1 SyringeA syringe equipped with a male fittingwith a minimum capacity of 2 mL.7.1.10.2 AutosamplerAn autosampling system capable ofprecise delivery, equipped with a dust cover to reduce airb
43、ornecontamination.7.2 Eluent and Regenerant ReservoirsSelect containerswitha4to20Lcapacity that are designed to minimizeintroduction of air into the flow system for storing eluents andregenerants.7.3 GlasswareGlassware, including volumetric pipettesand flasks, must be dedicated for use on atmospheri
44、c wetdeposition samples only. Volumetric pipettes should be used tomeasure the stock solutions.The pipettes may be either fixed orvariable volume and either glass or plastic. Volumetric glass-ware must meet the requirement for Class A items given inSpecification E 694. Pipettes with disposable tips
45、are preferredin order to reduce contamination. The pipettes must have aprecision and a bias of 1 % or better. Precision and bias aredetermined by weighing a minimum of ten separately pipettedaliquots.7.4 Laboratory FacilitiesLaboratories used for the analy-sis of wet deposition samples must be free
46、from sources ofcontamination. The use of laminar flow clean air work stationsis recommended for sample processing and preparation toavoid the introduction of airborne contaminants. Samples mustalways be capped or covered prior to analysis. A positivepressure environment within the laboratory is also
47、 recom-mended to minimize the introduction of external sources ofcontaminant gases and particulates. Room temperature fluctua-tions must be controlled to within 6C to prevent baseline driftand changes in detector response. Windows within the labora-tory must be kept closed at all times and sealed if
48、 air leaks areapparent. The use of disposable tacky floor mats at the entranceto the laboratory is helpful in reducing the particulate loadingwithin the room.8. Reagents and Materials8.1 Purity of ReagentsUse reagent grade or higher gradechemicals for all solutions. All reagents shall conform to the
49、specifications of the Committee on Analytical Reagents of theAmerican Chemical Society (ACS) where such specificationsare available.78.2 Purity of WaterUse water conforming to SpecificationD 1193, Type II. Point of use 0.2 m filters are recommendedfor all faucets supplying water to prevent the introduction ofbacteria ion exchange resins, or both, into reagents, standard4Dionex P/N 030986 (AG3) available from Dionex Corp., 1228 Titan Way, POBox 3603, Sunnyvale, CA, 94088-3603, or equivalent has been found to besatisfactory.5Dionex P/N 030985
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