Implementation of suitable flow injection/sequential injection on-line sample pretreatment schemes. Separation and preconcentration procedures for the determination of trace metal concentrations by ETAAS and/or ICPMS

Despite their excellent analytical chemical capacities, ETAAS and ICPMS, nevertheless, often require suitable pretreatment of the sample material in order to obtain the necessary sensitivity and selectivity. Either in order to separate/preconcentrate the analyte material, or because of the presence of potentially interfering matrix constituents. Such pretreatments are advantageously performed in flow injection (FI) or sequential injection (SI) manifolds, where all appropriate unit operations can be effected under enclosed and strictly controlled conditions. Various separation/preconcentration procedures are feasible, such as liquid-liquid extraction, (co)precipitation with collection in knotted reactors, adsorption, hydride generation, or the use of ion-exchange columns. Apart from hydride generation, where the analyte is converted into a gaseous species, the common denominator for these approaches is that the analyte material finally is contained within a well-defined small volume of eluate, which then is introduced into the analytical instruments. While the graphite tube of the ETAAS only can accommodate up to 50 mul solution, yet might tolerate organic but preferably should be subjected to inorganic eluates, the ICPMS has potentially a larger volumetric capacity yet cannot accept organic solvents as these adversely will impair its performance. In the lecture, selected examples of separation/preconcentration FI/SI-procedures will be presented, with particular emphasis on the use of the novel “lab-on-valve” concept.