Materials and Methods

Anomalously high blank values (1000 x normal) have been observed when cold-vapor atomic absorption analysis for total mercury follows analysis for inorganic mercury. The origin of this unexpected phenomenon Is considered to be accumulated chemlsorption and possible deep embedment of mercury from previous samples within the reaction vessel. Detection of this mercury follows CdCla-induced desorption. Precautionary measures are suggested. Introduct ion Cold-vapor atomic absorption analysis is a simple and widely used method for routinely analyzing large numbers of biologi-cal samples for mercury content. Since Magos introduced the cadmium chloride reagent o break carbon-mercury bonds (1), it has become possible to determine both organic and inorganic mercury by this method. When members of our laboratory turned to the analysis of organic mercury after a period of analyzing only inorganic forms, the background signal increased by a factor of 1000--a signal corresponding to greater than 1.0 ug/mL * when no mercury was supposed to be present. The purpose of this paper is two-fold. The first, and perhaps most important, is to alert users of CVAA analysis of mercury that this problem exists. If CVAA apparatus has been used only for inorganic analysis, the switch to total analysis using the cadmium chloride reagent is likely to give signals several orders of magnitude too high. The second purpose is to report our in-vestigation of this unexpected phenomenon, to determine its origin, and to ascertain how the problem can be eliminated