UV photochemical vapor generation of Cd from a formic acid based medium: optimization, efficiency and interferences

Abstract

Cadmium ultraviolet photochemical vapor generation was investigated using a 6 W low pressure Hg lamp, with a coiled quartz reactor and atomic fluorescence spectrometric detection. Volatile species of cadmium can be reproducibly generated from a formic acid based medium with the addition of ferrous ions, which enhances the generation efficiency some 2.6-fold. Further improvement can be achieved by increasing the pH of the medium to 2.7 and through the addition of Triton X-100 downstream of the reactor. The overall generation efficiency was estimated by two approaches; from the remaining waste, to be 17.3% (SD 2.2%) and from a comparison of the response to direct solution nebulization coupled to an inductively coupled plasma mass spectrometer, to be 5.5% (SD = 0.2%). A limit of detection of 1.8 ng mL⁻¹ and repeatability (RSD) of 2.1% at 250 ng mL⁻¹ were achieved with atomic fluorescence spectrometric detection. Severe interferences were observed from nitric acid and nitrates as well as from the –SH group containing compounds and selected chalcogens, which makes the routine application of this methodology difficult.