Automated flow analysis system based on multicommutation for Cd, Ni and Pb on-line pre-concentration in a cationic exchange resin with determination by inductively coupled plasma atomic emission spectrometry - Miranda, C E S; Reis, Boaventura Freire dos; Baccan, Nivaldo; Packer, A P; Giné-Rosias, Maria Fernanda Georgina (Analytica Chimica Acta, 2002)