1、Designation: D 5086 01Standard Test Method forDetermination of Calcium, Magnesium, Potassium, andSodium in Atmospheric Wet Deposition by Flame AtomicAbsorption Spectrophotometry1This standard is issued under the fixed designation D 5086; the number immediately following the designation indicates the
2、 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is applicable to the determinatio
3、n 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 (see Table 1 for a
4、 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 singleoperator pre
5、cision (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 This standard does not purport to ad
6、dress 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 warningstatements are given in 8.3, 8.7, 12.1
7、.8, and 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 ofApp
8、licable Methods of Committee D19 on WaterD 4453 Practice for Handling of Ultra-Pure Water SamplesD 4691 Practice for Measuring Elements in Water by FlameAtomic Absorption SpectrophotometryD 5012 Guide for Preparation of Materials Used for theCollection and Preservation of Atmospheric Wet Deposi-tion
9、E 131 Terminology Relating to Molecular SpectroscopyE 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near Infrared Spectrophotom-etersE 694 Specification for Laboratory Glass Volumetric Appa-ratusIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units
10、(SI): The Modern Metric System3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminologies D 883, D 1129, D 1356, E 131,and Practices D 4691, E 275, and IEEE/ASTM SI 10.3.1.1 method detection limit, MDLthe minimum concen-tration of an analyte that can be repo
11、rted 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 concentration near the low standard.The analyte concentration of this solution should not be greaterthan ten times the estimated M
12、DL.4. 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 over a series of ve
13、ry narrow, sharply defined wave-lengths from a distinct line source of light, usually a hollowcathode lamp specific to the metal of interest, passed through1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.03 on Ambie
14、ntAtmospheres and Source Emissions.Current edition approved March 10, 2001. Published May 2001. Originallypublished as D 5086 90. Last previous edition D 5086 95.2The boldface numbers in parentheses refer to a list of references at the end ofthis test method.3For referenced ASTM standards, visit the
15、 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 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, U
16、nited States.the flame. Light from the source beam, less whatever intensitywas absorbed by the atoms of the metal of interest, is isolatedby the monochromator and measured by the photodetector. Theamount of light absorbed by the analyte is quantified bycomparing the light transmitted through the fla
17、me to lighttransmitted by a reference beam. The amount of light absorbedin the flame is proportional to the concentration of the metal insolution. The relationship between absorption and concentra-tion is expressed by Beers Law:log Io/I! 5 abc 5 A (1)(1)where:Io= incident radiant power,I = transmitt
18、ed radiant power,a = absorptivity (constant for a given system),b = sample path length,c = concentration of absorbing species, andA = absorbance.The atomic absorption spectrophotometer is calibrated withstandard solutions containing known concentrations of theelement(s) of interest. The concentratio
19、n of each analyte in theunknown sample is determined from contructed calibrationcurves.5. Significance and Use5.1 This test method may be used for the determination ofcalcium, magnesium, potassium, and sodium in atmosphericwet deposition samples.5.2 Emphasis is placed on the easily contaminated qual
20、ity ofatmospheric wet deposition samples due to the low concentra-tion levels of dissolved metals commonly present.5.3 Annex A1 represents cumulative frequency percentileconcentration plots of calcium, magnesium, potassium, andsodium obtained from analyses of over five thousand wetdeposition samples
21、. These data may be used as an aid in theselection of appropriate calibration standard concentrations. (3)6. Interferences6.1 A chemical interference can prevent, enhance, or sup-press the formation of ground state atoms in the flame. Forexample, in the case of calcium determinations, the presence o
22、fphosphate or sulfate can result in the formation of a salt thathinders proper atomization of the solution when it is aspiratedinto the flame. This decreases the number of free, ground stateatoms in the flame, resulting in lowered absorbance values.Aluminum can cause a similar interference when meas
23、uringmagnesium. The addition of appropriate complexing agents,such as lanthanum, to the sample solution reduces or eliminateschemical interferences and may increase the sensitivity of thistest method.6.2 Alkali metals, such as potassium and sodium, canundergo ionization in an air-acetylene flame res
24、ulting in adecrease in ground state atoms available for measurement byatomic absorption. The addition of a large excess of an easilyionizable element, such as cesium, will eliminate this problem,since cesium will be preferentially ionized. The preferentialionization of the cesium results in an enhan
25、ced atomic absorp-tion signal for both 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 elevatedrea
26、dings due to residual metal from the previous 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 oft
27、he system is ascertained by aspirating water until the absor-bance readout returns to the baseline.TABLE 1 Interlaboratory Precision and Bias for Calcium, Magnesium, Potassium, and Sodium Determined from Analyte Spikes ofSynthetic Atmospheric Wet Deposition SamplesElementNumber ofObservationsAmountA
28、dded,mg/LMeanRecovery,mg/LStA95 %ReproducibilityLimitSoB95 %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 0.03
29、8 0.106 0.025 0.070 0.114 7.87 yes20 2.939 2.770 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 0.0
30、0 0.00 no17 0.682 0.696 0.012 0.034 0.0037 0.010 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 0.0
31、25 0.070 0.014 0.039 0.008 1.60 noNa 18 0.225 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 0.05
32、0 5.52 yes22 1.84 1.85 0.041 0.115 0.021 0.059 0.01 0.54 noABetween laboratory precision, reproducibility.BWithin laboratory precision (pooled single operator precision), repeatability.D50860126.4 Atmospheric wet deposition samples are characterizedby low ionic strength and rarely contain enough sal
33、ts to causeinterferences due to non-specific background absorbance. Theuse of background correction techniques is not necessary andwill decrease the signal to noise ratio and lessen precision.7. Apparatus7.1 Atomic Absorption SpectrophotometerSelect adouble-beam instrument having a monochromator, ph
34、otodetec-tor, pressure-reducing valves, adjustable spectral bandwidth,and a wavelength range of 190 to 800 nm. Peripheral equip-ment may include a strip chart recorder or a suitable datasystem.7.1.1 BurnerUse a long-path, single slot, air-acetyleneburner head supplied by the manufacturer of the spec
35、tropho-tometer.7.1.2 Hollow Cathode LampsSingle element lamps arerecommended. Multi-element lamps are available but are notrecommended. They have a shorter lifespan, are less sensitive,require a higher operating current, and increase the chances ofspectral interferences.7.1.3 MonochromatorTo increas
36、e the sensitivity for cal-cium and potassium measurements, a monochromatorequipped with a blaze grating in the range of 500 to 600 nm isrecommended. 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
37、 to900 nm) photomultiplier tube is recommended. Select a red-sensitive photomultiplier tube to detect potassium at 766.5 nmand to increase sensitivity for calcium at 422.7 nm.7.2 Volumetric PipetsMaintain a set of ClassAvolumetricpipets (see Specification E 694) to be used only when makingdilute cal
38、ibration solutions for the analysis of atmospheric wetdeposition samples. Alternatively, disposable tip pipets may beused.7.3 Volumetric FlasksMaintain a set of Class A volumet-ric flasks (see Specification E 694) to be used only whenmaking dilute calibration solutions for the analysis of atmo-spher
39、ic wet deposition samples.7.3.1 The first time any glassware is used for making stocksolutions and standards, clean with HCl (1+1) and rinsethoroughly 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 atmos
40、pheric wet deposition samples should be free fromexternal sources of contamination.7.4.1 The use of laminar flow clean air workstations isrecommended for sample processing and preparation to avoidthe introduction of airborne contaminants. If a clean airworkstations is unavailable, samples must be ca
41、pped or cov-ered prior to analysis.7.4.2 A positive pressure environment within the laboratoryis recommended to minimize the introduction of externalsources of contaminant gases and particulates. Windows withinthe laboratory should be kept closed at all times and sealed ifleaks are apparent.7.4.3 Th
42、e 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 thespecifications of the Comm
43、ittee on Analytical Reagents of theAmerican Chemical Society (ACS) where such specificationsare available.48.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type I of Specification D 1193. Point of use 0.2 m filtersare recommende
44、d for all faucets supplying water to prevent theintroduction of bacteria and/or ion exchange resins into re-agents.8.3 Acetylene (Fuel)Minimum acceptable 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-purifi
45、ed grades that contain a proprietary solvent can beused to 207 kPa (30 psig) before replacement. Avoid introduc-ing these solvents into the instrument. Damage to the instru-ments plumbing system can result. To prevent solvent carry-over, allow acetylene cylinders to stand for at least 24 h beforeuse
46、. (WarningAcetylene is a highly flammable gas. Followthe precautions in 9.3-9.6 regarding safe operating pressures,suitable plumbing, and operator safety.)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 ro
47、om temperature in a high densitypolyethylene or polypropylene container.8.5 Hydrochloric Acid (1+1)Carefully add one volume ofconcentrated hydrochloric 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)
48、 to 900 mL ofwater and dilute to 1 L.8.7 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. Cool the solution betwe
49、en additions. Dilute to 1 L withwater. Store at room temperature in a high density polyethyleneor polypropylene container. (WarningDissolving lanthanumoxide in hydrochloric acid is a strongly exothermic reaction;use extreme caution when dissolving the reagent. Refer to 9.1for proper safety precautions when preparing this solution.)8.8 Oxidant (air)The air may be provided by a compres-sor or commercially bottled supply. Remove oil, water, andother foreign matter from the air using a filter recommended bythe manufacturer. Refer
