The stability of instrument calibration standards for Inductively Coupled Plasma/Atomic Emission Spectrometric analysis was studied over a two-year period. Data were obtained as functions of analyte concentration, acid type, and acidity. The impact of acid concentration on signal-to-background ratios was also assessed. The results show that, with the appropriate choice of inorganic acid preservatives, most analytes maintain their integrity over extended periods; thus frequent standard

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... ns are not necessary to obtain valid analytical data. This conclusion allows for more efficient use of commercially purchased reference materials, " which should reduce procurement costs and minimize chemical waste. DI6T_TION OF THIS DOCUMENT 1,_UNL_"_ITIE) o *Work submitted by theU.S. Department of EnergyunderContract W-31-109-Eng.38.