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determmatlon of trace elements Background must be measured adjacent to analyte Imes on samples during analysIs The position selected for the background intensity measurement on either or both sides of the analytical line, will be determmed by the complexity of the spectrum adjacent to the analyte line The position used must be free of spectral Interference and reflect the same change In background intensity as occurs at the analyte wavelength measured Background correction IS not required m cases of line broadening where a background correction measurement would actually degrade the analytical result The POSSibility of additional Interferences named In 5 1 (and tests for their presence as descnbed In 5 2) should also be recognized and appropnate corrections made venfy background and Interelement correction factors (See 7 6 2) 3 9 Quahty control sample - solution obtained from an outSide source having known, concentration values to be used to venfy the cahbratlon standards (See 7 6 3) 3 10 Cahbratlon standards - a senes of know standard solutions used by the analyst for calibration of the Instrument (I e , preparation of the analytical curve) (See 74) 3 11 Linear dynamic range - The concentration range over which the analytIcal curve remains linear 3 12 Reagent blank - A volume of deionized distilled water containing the same aCid matnx as the cahbratlon standards carned through the entire analytical scheme (See 752) 3 13 Calibration blank - A volume of deionIzed distilled water aCidified WIth HN03 and HCI (See 7 5 1) 3 14 Method of standard addition - The standard addition technIque Involves the use of the unknown and the unknown plus a known amount of standard (See 10 6 1) unresolved overlap of molecular band spectra, 3) background contnbutlon from continuous or recombination phenomena, and 4) background contribution from stray hght from the line emiSSion of high concentration elements The first of these effects can be compensated by utiliZing a computer correction of the raw data, requlnng the monltonng and measurement of the Interfenng element The second effect may reqUire selectIOn of an alternate wavelength The third and fourth effects can usually be compensated by a background correction adjacent to the analyte line In addition, users of Simultaneous multielement instrumentation must assume the responSibility of venfymg the absence of spectral Interference from an element that could occur In a sample but for which there IS no channel In the Instrument array Listed In Table 2 are some Interference effects for the recommended wavelengths given In Table 1 The data In Table 2 are Intended for use only as a rudimentary gUide for the indication of potential spectral Interferences For thiS purpose, linear relations between concentration and intensIty for the analytes and the Interferents can be assumed The Interference information which 1 was collected at the Ames Laboratory, IS expressed at analyte concentration eqlvalents (I e false analyte concen- trations) anslng from 100 mg/L of the Interferent element The suggested use of thiS informatIon IS as follows Assume that arsenic (at 193 696 nm) IS to be determined In a sample containing approXimately 10 mg/L of aluminum Accordmg to Table 2,100 mg/L of aluminum would yield a false SIgnal for arsenic eqUivalent to approximately 1 3 mg/L Therefore, 10 mg/L of aluminum would result In a false Signal for arsenic eqUivalent to approximately 0 13 mg/L The reader IS cautioned that other analytical systems may exhibit somewhat different levels of Interference than those shown In Table 2, and that the Interference effects must be evaluated for each indiVidual system Only those Interferents listed werp investigated and the blank spaces In Table 2 indicate that measurable inter- ferences were not observed for the Interferent concentrations listed In Table 3 Generally Interferences were discernible If they produced peaks or background shifts correspondmg to 2-5% of the peaks generated by the 'Ames Laboratory USDOE Iowa State University Ames Iowa 50011 Definitions 3 2 Suspended - Those elements which are retained by a 045 pm membrane filter 3 3 3 Dissolved - Those elements 3 1 which will pass through a 045 pm membrane filter The concentration Total - determined on an unfiltered sample follOWing vigorous digestion (9 3) or the sum of the dissolved plus suspended concentrations (9 1 plus 9 2 ) 34 concentration determined on an unfiltered sample follOWing treatment with hot dilute minerai aCid (9 4) 3 5 Instrumental detection limit - The concentratIon equivalent to a Signal, due to the analyte which IS equal to three times the standard deviation of a senes of ten rephcate measurements of a reagent blank Signal at the same wavelength 4 1 each reagent used In thiS method has not been precisely defined however each chemical compound should be treated as a potential health hazard From thiS vlewpomt exposure to these chemicals must be reduced to the lowest pOSSIble level by whatever means available The laboratory IS responsible for maintaining a current awareness file of OSHA regulations regarding the safe handling of the chemIcals specified In thiS method A reference file of matenal data handling sheets should also be made available to all personnel Involved In the chemical analySIS Additional references to laboratory safety are available and have been Identified (147 148 and 149) for the information of the analyst Total recoverable - The 3 6 SensItivity - The slope of the analytical curve, I e functional relationship between emiSSIOn intensity and concentratIOn 3 7 Instrument check standard - multielement standard of known concentratIons prepared by the analyst to mOnitor and venfy Instrument performance on a dally basIs (See 7 6 1) A Interferences 5 1 1 Spectral mterferences can be categonzed as 1) overlap of a spectral hne from another element, 2) 3 8 Interference check sample - A solution containing both Interfermg and analyte elements of known concentration that can be used to 4 Safety The tOXICity or carclnogemclty of 5 5 1 effects may contnbute to inaccuracies In the determinatIOn of trace elements They can be summanzed as follows Dec 1982 Metals-21 Several types of Interference APDF Image | Methods for Chemical Analysis of Water and Wastes
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