Integration Errors in the Quantitative Evaluation of Flat Bed Separations

Abstract

Journal of Liquid ChromatographyPublication details, including instructions for authors and subscription information: ABSTRACT The paper discusses sources of errors which affect the accuracy of optical densitometry for the quantitative evaluation of TL chromatograms and flat bed electropherograms. Both 1D and 2D separations are considered. Relevant error sources fall into two classes. One which is deterministic in nature and one which has stochastic character. The main source of deterministic errors is the non-linear relation between densitometric response and concentration distribution. Linearizing transforms of the reponse signal are available which significantly reduce the magnitude of the error. They are most effective when ('point" scanning is used but much less so with slit scanning. stochastic sources produce noise which affects the measured value of the signal arnplitude. Most important is generally the "optical" noise of the blank medium.In most cases it is this factor, which ultimately determines sensitivity and accuracy of the method. Efforts to reduce optical noise are, therefore, an important design feature for high performance instrument. Most effective in this regard is two wave lengths scanning. The technique is, however, applicable only if the response characteristic of the medium is spectrally flat over a range which is significantly wider than the spectral absorbance characteristic of the separate. 1403