GAS GENERATION AND PRECONCENTRATION COUPLED TO GAS-PHASE MOLECULAR ABSORPTION SPECTROMETRY - A POWERFUL TOOL FOR THE SIMULTANEOUS DETERMINATION OF ANALYTES FORMING VOLATILE COMPOUNDS

Different methods for a simultaneous determination of several analytes forming volatile compounds at room temperature are described. The mai n steps of these methods are: continuous generation, collection in a c ryogenic trap, revolatilization, measurement of the volatile compounds by Gas Phase Molecular Absorption Spectrometry and resolution by mult i-wavelength methods. Several mixtures containing 2, 3 or 4 components have been studied: 1) elements forming covalent hydrides; 2) arsenic organometallic compounds forming volatile gases with a similar structu re to arsine; and 3) sulphur species that can evolve volatile compound s. Under the optimum conditions obtained for each mixture, detection l imits range from 0.8 ng/m.L (dimethylarsinic acid) to 2 mu g/mL (SCN-) .