Flow-injection analysis with Fourier transform infrared spectrometric detection: a potential tool for the analysis in complex matrices

Abstract

The combination of flow-injection analysis (FIA) with FT-IR spectrometry as detector is discussed for the determination of glucose in aqueous samples. Time-domain and frequency-domain signal processing are compared and frequency-domain signal processing is found to give superior qualitative and quantitative information. With frequency-domain signal processing, the enzymatic degradation of glucose can be used for its measurement. This method is shown to be successfully applicable in the physiologically interesting concentration range (50–500 mg dl −1). For the quantitative measurement, the difference signal of the sample before and after the reaction is evaluated. Although this approach should theoretically render the method insensitive towards other sample constituents, even with glucose-fructose mixtures severe interferences exist. A possible explanation is the influence on the background spectrum by the pH shift occurring during the reaction.