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.