Precision-Optimization of Wavelengths in Diode-Array Detection in Separation Science

Abstract

With the theoretically predicted relative standard deviation (RSD) of measurements as a criterion, the ultra-violet detection wavelengths are optimized in a capillary electrophoresis system equipped with a diode-array, when analyte signals are baseline-separated in the time-direction and the measurements are the integration results in the time and wavelength directions. Some cold drugs and additives are taken as examples. The auto-correlation of an instrumental baseline at a diode (time-correlation) and the cross-correlation of measurements between different diodes (wavelength- correlation) are both taken into account for a better prediction of RSD. A simple method for estimating the wavelength- correlation is presented with a theoretical proof. This paper also shows that the measurement precision is governed to a large extent by the zero level setting of the time integration which accumulates the instrumental output relative to the zero level. The optimum (minimum RSD) is selected from among the wavelengths (190-300nm) and possible zero level settings. The validity of the RSD prediction is statistically verified.