Supported liquid membrane coupled on-line to potentiometric stripping analysis at a mercury-coated reticulated vitreous carbon electrode for trace metal determinations in urine

A method for trace metal determinations in complex matrices is presented, The method combines supported liquid membrane (SLM) sample clean-up and enrichment with potentiometric stripping analysis (PSA) in a flow system using reticulated vitreous carbon (RVC) as the electrode material, The membrane contained 40% mim di-2-ethylhexylphosphoric acid dissolved in kerosene, Lead was used as a model substance in high-purity water and urine samples. The samples were enriched after a simple pH adjustment, The SLM enrichment time was 10 min when the last 5 min electrodeposition on the RVC electrode at -1.0 V (versus Ag/AgCl) was performed simultaneously, The influence of various experimental parameters such as deposition time, deposition potential and flow rate on the lead signal was investigated, With a 10 min SLM enrichment including a 5 min deposition time, the detection limit for lead was 0.3 mu g l(-1), The relative standard deviation for lead concentrations in the range 4-20 mu g l(-1) was 0.05%, The overall SLM-PSA system was found to be stable for at least 100 urine analyses, The method was validated by running a reference urine sample, The result obtained (five replicates) was 9.7 mu g l(-1) (standard deviation 1.8 mu g l(-1)) which is within the recommended range of 9.2-10.8 mu g l(-1).