Purge and trap thermal desorption device for the determination of dimethylselenide and dimethyldiselenide

A method is described for the determination of dimethylselenide and dimethy ldiselenide using a purge-and-trap/thermal desorption device (PT/TD) couple d to a capillary column gas chromatograph with a six-way Valco valve. The s ystem is constructed in such a way that it allows also on-column injections of the volatile compounds in organic solvents for external calibration pur poses without the need to disassemble the PT/TD. The influence of the purge flow, purge time and volume of sample, on the purge efficiency of the PT s ystem is studied. Desorption time and temperature are optimised for the TD mode of operation. Atomic absorption spectrometry (AAS) and flame photometr ic detection (FPD) have been used for the final determination of the volati le compounds. The figures of merit achieved with both detectors are reporte d.