reagents were of analytical grade
unless otherwise stated. Hydrogen tetrachloroaurate trihydrate (min.
99.9%), PESTANAL analytical standards of dithiocarbamate fungicides
(Thiram and Propineb) and organophosphate pesticides (Phorate and
Methamidophos), zofenopril calcium, arginine, asparagine, aspartic
acid,
glutamic acid, ammonium chloride, lactic acid, magnesium sulfate,
magnesium chloride hexahydrate, sodium sulfide, sodium chloride, sodium
sulfate, sodium bicarbonate, dipotassium hydrogen phosphate, potassium
dihydrogen phosphate, citric acid, tri-sodium citrate, potassium chloride,
calcium chloride dehydrate, uric acid,
creatinine were obtained from Sigma-Aldrich (Steinheim, Germany).
Germany). Glycine, histidine, lysine, and valine were supplied by
Serva Electrophoresis GmbH (Heidelberg, Germany). Finally, urea (>99.5%)
was purchased from Pharmacia Biotech AB (Uppsala, Sweden) and HPLC-grade
solvent from Fischer Scientific (Loughborough, U.K.).