Determination of trace amounts of mercury vapour in humid air:: performance of gold traps in an atomic fluorescence system

A method has been developed for determination of mercury vapour in end-exhaled air. Mercury vapour was preconcentrated by amalgamation on a sampling tube filled with gold impregnated silica (Amasil). A small air-sampling volume (100-500 ml) was collected and the analysis was-performed using a two stage amalgamation technique combined with atomic fluorescence detection. The procedure is fast and simple. The precision (repeatability) obtained in laboratory experiments was generally less than 10% (relative standard deviation) with linearity up to at least 7200 pg. The recovery was better than 97% up to 4000 pg per sample. The system has a quantification limit of 4 pg and therefore mercury vapour can be monitored at background levels. The efficiency of the sampling tubes was not affected by sampling in humid air (RH > 95%), The developed storage technique, using parafilm to cover the ends of the tubes and storage in a refrigerator, showed low blank levels on the tubes and no losses from sampled tubes for a storage time of at least one meek. No carry-over in the sampling device or breakthrough on the sample tubes could be detected up to 11 500 pg l(-1). In two subjects, without amalgam fillings, the within-day variations of end-exhaled mercury were below 15%, The average mercury concentrations in the end-exhaled air were 10 and 33 pg l(-1), respectively. In an occupationally exposed worker the concentration was 900 pg l(-1).