1、Designation: D5086 01 (Reapproved 2013)Standard Test Method forDetermination of Calcium, Magnesium, Potassium, andSodium in Atmospheric Wet Deposition by Flame AtomicAbsorption Spectrophotometry1This standard is issued under the fixed designation D5086; the number immediately following the designati
2、on 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 is applicable to t
3、he determination ofcalcium, magnesium, potassium, and sodium in atmosphericwet deposition (rain, snow, sleet, and hail) by flame atomicabsorption spectrophotometry (FAAS). (1)21.2 The concentration ranges are listed below. The rangetested was confirmed using the interlaboratory collaborativetest (se
4、e Table 1 for a statistical summary of the collaborativetest).MDL(mg/L) (2)Range of Method(mg/L)Range Tested(mg/L)Calcium 0.009 0.033.00 0.1682.939Magnesium 0.003 0.011.00 0.0390.682Potassium 0.003 0.011.00 0.0290.499Sodium 0.003 0.012.00 0.1051.841.3 The method detection limit (MDL) is based on sin
5、gleoperator precision (2) and may be higher or lower for otheroperators and laboratories. Many workers have found that thistest method is reliable at lower levels than were tested, but theprecision and bias data presented are insufficient to justify theiruse at lower levels.1.4 The values stated in
6、SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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 healt
7、h practices and determine the applica-bility of regulatory limitations prior to use. Specific warningstatements are given in 8.3, 8.7, 12.1.8, and Section 9.2. Referenced Documents2.1 ASTM Standards:3D883 Terminology Relating to PlasticsD1129 Terminology Relating to WaterD1193 Specification for Reag
8、ent WaterD1356 Terminology Relating to Sampling and Analysis ofAtmospheresD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD4453 Practice for Handling of High Purity Water SamplesD4691 Practice for Measuring Elements in Water by FlameAtomic Ab
9、sorption SpectrophotometryD5012 Guide for Preparation of Materials Used for theCollection and Preservation of Atmospheric Wet Deposi-tionE131 Terminology Relating to Molecular SpectroscopyE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible SpectrophotometersE694 Specific
10、ation for Laboratory Glass Volumetric Appa-ratusIEEE/ASTM SI-10 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, referto Terminologies D883, D1129, D1356, E131, and PracticesD4691
11、, E275, and IEEE/ASTM SI-10.3.1.2 method detection limit, MDLthe minimum concen-tration of an analyte that can be reported with 99 % confidencethat the value is above zero based on a standard deviation ofgreater than seven repetitive measurements of a solutioncontaining the analyte at a concentratio
12、n near the low standard.The analyte concentration of this solution should not be greaterthan ten times the estimated MDL.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.
13、Current edition approved Oct. 1, 2013. Published October 2013. Originallyapproved in 1990. Last previous edition approved in 2008 as D5086 01(2008).DOI: 10.1520/D5086-01R13.2The boldface numbers in parentheses refer to a list of references at the end ofthis test method.3For referenced ASTM standards
14、, 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194
15、28-2959. United States14. Summary of Test Method4.1 Asolution containing the metal(s) of interest is aspiratedas a fine mist into an air acetylene flame where it is convertedto an atomic vapor consisting of ground state atoms. Theseground state atoms are capable of absorbing electromagneticradiation
16、 over a series of very narrow, sharply defined wave-lengths from a distinct line source of light, usually a hollowcathode lamp specific to the metal of interest, passed throughthe flame. Light from the source beam, less whatever intensitywas absorbed by the atoms of the metal of interest, is isolate
17、dby the monochromator and measured by the photodetector. Theamount of light absorbed by the analyte is quantified bycomparing the light transmitted through the flame to lighttransmitted by a reference beam. The amount of light absorbedin the flame is proportional to the concentration of the metal in
18、solution. The relationship between absorption and concentra-tion is expressed by Beers Law:logIo/I! 5 abc 5 A (1)where:Io= incident radiant power,I = transmitted radiant power,a = absorptivity (constant for a given system),b = sample path length,c = concentration of absorbing species, andA = absorba
19、nce.The atomic absorption spectrophotometer is calibrated withstandard solutions containing known concentrations of theelement(s) of interest. The concentration of each analyte in theunknown sample is determined from contructed calibrationcurves.5. Significance and Use5.1 This test method may be use
20、d for the determination ofcalcium, magnesium, potassium, and sodium in atmosphericwet deposition samples.5.2 Emphasis is placed on the easily contaminated quality ofatmospheric wet deposition samples due to the low concentra-tion levels of dissolved metals commonly present.5.3 Annex A1 represents cu
21、mulative frequency percentileconcentration plots of calcium, magnesium, potassium, andsodium obtained from analyses of over five thousand wetdeposition samples. These data may be used as an aid in theselection of appropriate calibration standard concentrations. (3)6. Interferences6.1 A chemical inte
22、rference can prevent, enhance, or sup-press the formation of ground state atoms in the flame. Forexample, in the case of calcium determinations, the presence ofphosphate or sulfate can result in the formation of a salt thathinders proper atomization of the solution when it is aspiratedinto the flame
23、. This decreases the number of free, ground stateatoms in the flame, resulting in lowered absorbance values.Aluminum can cause a similar interference when measuringmagnesium. The addition of appropriate complexing agents,such as lanthanum, to the sample solution reduces or eliminateschemical interfe
24、rences and may increase the sensitivity of thistest method.6.2 Alkali metals, such as potassium and sodium, canundergo ionization in an air-acetylene flame resulting in adecrease in ground state atoms available for measurement byatomic absorption. The addition of a large excess of an easilyionizable
25、 element, such as cesium, will eliminate this problem,TABLE 1 Interlaboratory Precision and Bias for Calcium, Magnesium, Potassium, and Sodium Determined from Analyte Spikes ofSynthetic Atmospheric Wet Deposition SamplesElementNumber ofObservationsAmountAdded,mg/LMeanRecovery,mg/LStA95 %Reproducibil
26、ityLimitSoB95 %RepeatabilityLimitBias,mg/LBias,%Significantat 5 % LevelCa 18 0.168 0.160 0.0062 0.017 0.0063 0.018 0.008 4.76 yes21 0.382 0.332 0.027 0.076 0.011 0.031 0.030 7.85 yes19 0.769 0.722 0.018 0.050 0.0091 0.025 0.047 6.11 yes21 1.448 1.334 0.038 0.106 0.025 0.070 0.114 7.87 yes20 2.939 2.
27、770 0.047 0.132 0.037 0.104 0.169 5.75 yesMg 18 0.039 0.037 0.0033 0.0092 0.0016 0.0045 0.002 5.13 yes17 0.089 0.090 0.0061 0.017 0.0019 0.0053 0.001 1.12 no15 0.178 0.180 0.0057 0.016 0.0029 0.0081 0.002 1.12 no17 0.336 0.336 0.014 0.039 0.0038 0.011 0.00 0.00 no17 0.682 0.696 0.012 0.034 0.0037 0.
28、010 0.014 2.05 yesK 16 0.029 0.043 0.0036 0.010 0.0032 0.0090 0.014 48.3 yes16 0.065 0.068 0.0046 0.013 0.0012 0.0034 0.003 4.62 yes15 0.130 0.132 0.013 0.036 0.0038 0.011 0.002 1.54 no17 0.246 0.239 0.020 0.056 0.010 0.028 0.007 2.84 no17 0.499 0.507 0.025 0.070 0.014 0.039 0.008 1.60 noNa 18 0.225
29、 0.219 0.014 0.039 0.0056 0.016 0.006 2.67 no22 0.105 0.104 0.0010 0.027 0.0021 0.0059 0.001 0.95 no20 0.239 0.235 0.0053 0.015 0.0038 0.011 0.004 1.67 yes17 0.481 0.475 0.0070 0.020 0.0046 0.013 0.006 1.24 yes18 0.906 0.856 0.0087 0.024 0.0073 0.020 0.050 5.52 yes22 1.84 1.85 0.041 0.115 0.021 0.05
30、9 0.01 0.54 noABetween laboratory precision, reproducibility.BWithin laboratory precision (pooled single operator precision), repeatability.D5086 01 (2013)2since cesium will be preferentially ionized. The preferentialionization of the cesium results in an enhanced atomic absorp-tion signal for both
31、potassium and sodium.6.3 If a sample containing low concentrations of the metalbeing measured is analyzed immediately after a sample havinga concentration exceeding the concentration of the highestcalibration standard, sample carryover can result in elevatedreadings due to residual metal from the pr
32、evious sample. Toprevent this interference, routinely aspirate water for about 15s after a high concentration sample. Depending on the concen-tration of metal in the last sample analyzed, it may benecessary to rinse for longer time periods. Complete purging ofthe system is ascertained by aspirating
33、water until the absor-bance readout returns to the baseline.6.4 Atmospheric wet deposition samples are characterizedby low ionic strength and rarely contain enough salts to causeinterferences due to non-specific background absorbance. Theuse of background correction techniques is not necessary andwi
34、ll decrease the signal to noise ratio and lessen precision.7. Apparatus7.1 Atomic Absorption SpectrophotometerSelect adouble-beam instrument having a monochromator,photodetector, pressure-reducing valves, adjustable spectralbandwidth, and a wavelength range of 190 to 800 nm.Peripheral equipment may
35、include a strip chart recorder or asuitable data system.7.1.1 BurnerUse a long-path, single slot, air-acetyleneburner head supplied by the manufacturer of the spectropho-tometer.7.1.2 Hollow Cathode LampsSingle element lamps arerecommended. Multi-element lamps are available but are notrecommended. T
36、hey have a shorter lifespan, are less sensitive,require a higher operating current, and increase the chances ofspectral interferences.7.1.3 MonochromatorTo increase the sensitivity for cal-cium and potassium measurements, a monochromatorequipped with a blaze grating in the range of 500 to 600 nm isr
37、ecommended. For the analysis of magnesium and sodium, ablaze grating in the range of 200 to 250 nm is adequate.7.1.4 Photomultiplier TubeA wide spectral range (160 to900 nm) photomultiplier tube is recommended. Select a red-sensitive photomultiplier tube to detect potassium at 766.5 nmand to increas
38、e sensitivity for calcium at 422.7 nm.7.2 Volumetric PipetsMaintain a set of ClassAvolumetricpipets (see Specification E694) to be used only when makingdilute calibration solutions for the analysis of atmospheric wetdeposition samples. Alternatively, disposable tip pipets may beused.7.3 Volumetric F
39、lasksMaintain a set of ClassAvolumetricflasks (see Specification E694) to be used only when makingdilute calibration solutions for the analysis of atmospheric wetdeposition samples.7.3.1 The first time any glassware is used for making stocksolutions and standards, clean with HCl (1+1) and rinsethoro
40、ughly with water before use.7.3.2 Store clean glassware filled with water and covered.7.4 Laboratory FacilitiesLaboratories used for the analy-sis of atmospheric wet deposition samples should be free fromexternal sources of contamination.7.4.1 The use of laminar flow clean air workstations isrecomme
41、nded for sample processing and preparation to avoidthe introduction of airborne contaminants. If a clean airworkstations is unavailable, samples must be capped or cov-ered prior to analysis.7.4.2 A positive pressure environment within the laboratoryis recommended to minimize the introduction of exte
42、rnalsources of contaminant gases and particulates. Windows withinthe laboratory should be kept closed at all times and sealed ifleaks are apparent.7.4.3 The use of disposable tacky floor mats at the entranceto the laboratory is helpful in reducing the particulate loadingwithin the room.8. Reagents a
43、nd Materials8.1 Purity of ReagentsUse reagent grade or higher gradechemicals for all solutions. All reagents shall conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society (ACS) where such specificationsare available.48.2 Purity of WaterUnless otherwise in
44、dicated, referencesto water shall be understood to mean reagent water as definedby Type I of Specification D1193. Point of use 0.2 m filtersare recommended for all faucets supplying water to prevent theintroduction of bacteria and/or ion exchange resins into re-agents.8.3 Acetylene (Fuel)Minimum acc
45、eptable acetylene pu-rity is 99.5 % (v/v). Change the cylinder when the pressurereaches 517 kPa (75 psig) if the acetylene is packed in acetone.Pre-purified grades that contain a proprietary solvent can beused to 207 kPa (30 psig) before replacement. Avoid introduc-ing these solvents into the instru
46、ment. Damage to the instru-ments plumbing system can result. To prevent solventcarryover, allow acetylene cylinders to stand for at least 24 hbefore use. (WarningAcetylene is a highly flammable gas.Follow the precautions in 9.3 9.6 regarding safe operatingpressures, suitable plumbing, and operator s
47、afety.)8.4 Cesium Solution (Ionization Suppressant)Dissolve126.7 g cesium chloride (CsCl), dried at 105C for 1 h, in waterand dilute to 1 L. Store at room temperature in a high densitypolyethylene or polypropylene container.8.5 Hydrochloric Acid (1+1)Carefully add one volume ofconcentrated hydrochlo
48、ric acid (HCl, sp gr 1.19) to an equalvolume of water.8.6 Hydrochloric Acid (1+19)Carefully add 50 mL ofconcentrated hydrochloric acid (HCl, sp gr 1.19) to 900 mL ofwater and dilute to 1 L.4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For su
49、ggestions 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), Rockville,MD.D5086 01 (2013)38.7 Lanthanum Solution (Releasing Agent)In a glass 1 Lvolumetric flask, place 117.3 g of lanthanum oxide (La2O3),dried at 105C for 1 h. Wet with water and add HCl (1+1) insmall increments until a total of 500 mL of HCl (1+1) has beenadded. C
