Implementation of suitable FI/SI-sample separation/preconcentration schemes for determinations of trace-metal concentrations when using detection by ETAAS and ICPMS

Despite their excellent analytical chemical capacities, Electrothermal Atomic Absorption Spectrometry (ETAAS) and Inductively Coupled Plasma Mass Spectrometry (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 l solution, yet can tolerate inorganic as well as organic eluates, the ICPMS has a larger volumetric capacity yet cannot accept organic solvents as these adversely will impair its performance. Selected examples of separation/preconcentration FI/SI-procedures will be presented, with particular emphasis on the use of the novel “lab-on-valve” concept.