Application of a Wavelength Modulation Inductively Coupled Plasma-Echelle Spectrometer to Cd and Pb Determinations in Marine Samples

The installation and performance of a wavelength modulation system in a custom-built inductively coupled plasma-echelle spectrometer is described. The system, based on a computer-controlled rotatable quartz plate mounted just behind the entrance slit, permits extremely reproducible short (∼0.1 nm) wavelength scans in the vicinity of any chosen wavelength, as well as automatic two-point background subtraction during analyses. Its effectiveness, both in facilitating the characterization of spectroscopic interferences and in enabling accurate background correction, is demonstrated by determinations of trace quantities of cadmium and lead in biological tissues and sediments. Its potential use for wavelength modulation plasma emission spectrometry is discussed.