D 3919 – 04 ;RDM5MTK_.doc
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2、n American National StandardStandard Practice forMeasuring Trace Elements in Water by Graphite FurnaceAtomic Absorption Spectrophotometry1This standard is issued under the fixed designation D 3919; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
3、e 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. Scope*1.1 This practice covers the general considerations for the quantitative determination of tra
4、ce elements in water and wastewater by graphite furnace atomic absorption spectropho- tometry. Furnace atomizers are a most useful means of extend- ing detection limits; however, the practice should only be used at concentration levels below the optimum range of direct flame aspiration atomic absorp
5、tion spectrophotometry. Be- cause of differences between various makes and models of satisfactory instruments, no detailed operating instructions can be provided for each instrument. Instead, the analyst should follow the instructions provided by the manufacturer of a particular instrument.1.2 Wavel
6、engths, estimated detection limits, and optimum concentration ranges are given in the individual methods. Ranges may be increased or decreased by varying the volume of sample injected or the instrumental settings or by the use ofa secondary wavelength. Samples containing concentrations higher than t
7、hose given in the optimum range may be diluted or analyzed by other techniques.1.3 This technique is generally not applicable to brines and seawater. Special techniques such as separation of the trace elements from the salt, careful temperature control through ramping techniques, or matrix modificat
8、ion may be useful for these samples.1.4 The analyst is encouraged to consult the literature as provided by the instrument manufacturer as well as various trade journals and scientific publications.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its u
9、se. It is the responsibility 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: 2D 1129 Terminology Relating to WaterD 1192 Specification for Equipment
10、 for Sampling Water and Steam in Closed ConduitsD 1193 Specification for Reagent WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed Conduits D 4841 Practice for Estimation of Holding Time for Wate
11、r Samples Containing Organic and Inorganic ConstituentsD 5810 Guide for Spiking into Aqueous SamplesD 5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis3. Terminology3.1 DefinitionsFor definitions of terms used in this prac- tice, refer to Terminolo
12、gy D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 graphite furnacean electrothermal graphite device capable of reaching the specified temperatures required by the element being determined.3.2.2 platform or similar device a flat, grooved or un- grooved piece of pyrolytic graphite ins
13、erted in the graphite tube on which the sample is placed (1). 34. Summary of Practice4.1 The element is determined by an atomic absorption spectrophotometer used in conjunction with a graphite furnace. The principle is essentially the same as with direct flame aspiration atomic absorption except a f
14、urnace, rather than a flame, is used to atomize the sample. The elemental atoms to be measured are placed in the beam of radiation by increasing the1 This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.05 on Inorganic Constituent
15、s inWater.Current edition approved March 1, 2004. Published April 2004. Originally approved in 1980. Last previous edition approved in 1999 as D 3919 99.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
16、Standards volume information, refer to the standards Document Summary page on the ASTM website.3 The boldface numbers in parentheses refer to the list of references at the end ofthis standard.*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Har
17、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1D 3919 04temperature of the furnace, thereby causing the injected speci-men to be volatilized. Radiation from a given excited element is passed through the vapor containing ground-state atoms of that element. The decrease in in
18、tensity of the transmitted radiation is a measure of the amount of the ground-state element in the vapor. A monochromator isolates the character- istic radiation from the hollow-cathode lamp and a photosen- sitive device measures the attenuated transmitted radiation.4.2 Dissolved elements are determ
19、ined on a filtered sample with no pretreatment. See 9.5.4.3 Total recoverable elements are determined following acid digestion and filtration. If suspended material is not present, this digestion and filtration may be omitted.5. Significance and Use5.1 Elemental constituents in potable water, receiv
20、ing water, and wastewater need to be identified for support of effective pollution control programs. Currently, one of the most sensitive and practical means for measuring low concentrations of trace elements is by graphite furnace atomic absorption spectropho- tometry.6. Interferences6.1 Background
21、 absorption is caused by the formation of molecular species from the sample matrix that absorb or scatter the light emitted by the hollow cathode or electrodeless discharge line source. Without correction, this will cause the analytical results to be erroneously high. Three approaches exist for simu
22、ltaneous background correction: continuum source, Zeeman, and Smith-Hieftje.6.1.1 Continuum Source The continuum source procedure involves the use of a deuterium arc source for the ultraviolet ora tungsten halide lamp for the visible region of the spectrum. Light from the primary spectral source and
23、 the appropriate continuum source are alternately passed through the graphite furnace. Narrow-band emission of the primary source is affected by the scatter and background absorption from the matrix as well as the absorption of light by analyte atoms. The broadband emission of the continuum source i
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