Solid-phase microextraction method for gas chromatography with mass spectrometric and pulsed flame photometric detection: studies of organoarsenical speciation

The development, optimization, and application of a novel method for arsenic speciation based on capillary gas–liquid chromatography with simultaneous quadrupole ion-trap mass spectrometric (MS) detection and pulsed flame photometric detection (PFPD) is described. The method couples the sensitive arsenic-selectivity of PFPD with the structure elucidation capability of molecular MS detection for the determination of trace levels of unknown organoarsenicals in complex matrices. The conditions that affect the PFPD response in the presence of interfering species were optimized using the sequential Simplex algorithm for three key factors: gate delay (18.3 ms), gate width (9.1 ms), and combustion gas composition (16.6 ml/min H2). Complete discrimination in the PFPD of the arsenic signal from interfering S-, C-, and OH-emitting species that are problematic in existing methods was achieved. Additionally, a revised interpretation of our previously reported mechanism [J. Chromatogr. A 807 (1998) 253] for the dithiol derivatization and subsequent GC–MS determination of dimethylarsinic acid is presented.