STABILITY OF LOW-CONCENTRATION CALIBRATION STANDARDS FOR GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROSCOPY

Graphite furnace atomic absorption spectroscopy (GFAAS) is used for th e determination of ultra-trace metals in a wide variety of materials s uch as alloys, biological fluids and tissues, pure solvents and soluti ons, organic extracts, and environmental samples. The Statement of Wor k (SOW) for the U.S. Environmental Protection Agency (EPA) Contract La boratory Program (CLP) requires that low-concentration calibration sta ndards ''be prepared fresh daily or each time an analysis is made and discarded after use.'' This requirement results in significant cost to laboratories for chemicals, labor, and waste management. While EPA SW -846 is less prescriptive than CLP SOW, laboratories often follow the CLP requirements because criteria regarding the stability of GFAAS sta ndards have not been established. The objective of our study was to de termine the stability of both single and mixed analyte GFAAS standards for analytes commonly determined in our laboratory. Data were collect ed over nine months. The results show that GFAAS standards for Sb, Pb, Se, Ag, and Tl are stable for a longer period than currently assumed by the CLP SOW. Reducing the frequency at which these standards are pr epared will increase efficiency and reduce the handling of hazardous s ubstances, the quantity of hazardous waste generated, and the quantity of hazardous substances that must be ordered and stocked by the labor atory. These benefits will lead to improved safety, lowered costs, and reduced environmental concerns.