Evaluation of interference filters for spectral discrimination in solution-cathode glow discharge optical emission spectrometry

An inexpensive, computer-controlled wheel outfitted with several interference filters is evaluated as a spectral discrimination device for solution-cathode glow discharge (SCGD) optical emission spectrometry. Analytical performance of the instrument with wide-bandpass (10 nm) filters was critically compared to its performance with a traditional, narrow-bandpass monochromator (0.08 nm). With optimized spatial filtering, the SCGD-filter wheel (FW) instrument provided good precision (0.5-4.6% relative standard deviation), 1.5-4.9 orders of linear range, and limits of detection (LODs) that ranged from 0.5-450 ppb for the alkali and alkaline-earth metals, with both continuous sample introduction and 100 μL injections. Although the precision and upper limits of linearity of the instrument were comparable to those obtained with a traditional spectrometer, the LODs were 2-43 times higher (worse) and were strongly dependent upon the background emission accepted over the spectral bandpass of each filter. Despite the promising performance obtained during the initial analytical evaluation, application of the SCGD-FW instrument to complex samples was critically hindered by changes in background emission induced by the sample matrix, which could not be easily corrected. As a result of these interferences, the filter wheel, in its present form, seems unlikely to serve as a suitable alternative to a traditional spectrometer.