PRELIMINARY APPRAISAL OF A NOVEL SAMPLING AND STORAGE TECHNIQUE FOR THE SPECIATION ANALYSIS OF LEAD AND MERCURY IN SEAWATER

A sampling technique suitable for the preconcentration of lead and mercury species from seawater was developed and evaluated in this preliminary study. Seawater was first pumped through a tubular functional membrane at a flow rate of 2 ml min(-1) for adjustment of the sample pH. The analyte species were then enriched by solid-phase extraction in a microcolumn containing a resin with immobilized dithiocarbamate (DTC) groups. Optimum recoveries of alkyl- and inorganic lead species were obtained at a pH of about 7, whereas the enrichment efficiencies of alkyl- and inorganic mercury compounds were fairly independent of pH. The buffering membrane was effective in adjusting the pH of the seawater stream from its natural value of 8.1 to 7.1 prior to analyte enrichment on the DTC resin. Storage stability of the analyte species on the column was also studied, but found to be poor, indicating that elution from the DTC resin and further sample processing should commence as soon as possible after loading. Suggestions for further development and improvement of the proposed sampling technique are given.