The lonizable surface-group model Is applied to a sorbent consisting of 5-(phenylazo)-8-hydroxyqulnollne covalently bound to controlled pore glass (CPG-OXINE). Capacity measurements combined with Information from potentlometrlc

Complexatlon of Ca2+ by 5-(phenylazo)-8-hydroxyqulnollne bound to controlled pore glass (CPG-OXINE) Is described In terms of a modification of the Ionizable surface-group model to Include "site binding". Electrical properties of the surface are obtained by applying the Gouy-Chapman theory to data obtained from capacity measurements and potentiometrlc titrations of CPG-OXINE. The marked dependence of Ca2+ sorption on both pH and Ionic strength Is quantitatively explained. In addition, CPG-OXINE Is used as a sorbent In a column equilibration method to measure [Ca2+] In solutions containing labile calcium complexes with EDTA and the dlpeptlde carnoslne.Cation-exchange techniques have been used to measure the

A sample preparation procedure using 10% v/v HN03 was successfully applied to the determination of Pb, Cu and Hg in traditional Chinese medicines. It provides good recoveries of Pb, Cu and Hg, requires small volumes of concentrated acid and is free from reagent and procedural blank problems. A number of Chinese medicines were analysed using the proposed method. The results obtained were comparable to those obtained by other standard procedures. Using a 3 g sample, the detection limit for Pb was about 4 pg g-1, for Cu about 0.2 pg g-1 and for Hg about 0.03 pg g-1. The precision of the method, obtained by calculation of the relative standard deviations for six replicate measurements, was 0.7% for Pb, 0.7% for Cu and 6.5% for Hg.