AN INTERLABORATORY COMPARISON OF SAMPLE PRESENTATION METHODS FOR THE ANALYSIS OF AQUEOUS-SOLUTIONS USING FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Fourier transform infrared (FTIR) spectroscopy is becoming much more w idely used as an analytical technique. It appears to be particularly u seful for quantitative analysis, especially of aqueous solutions. Howe ver, there is a considerable variation in the cost and quality of inst rumentation as well as a large number of accessories for sample presen tation employing attenuated total reflectance (ATR). The objectives of the work reported in this paper were to investigate the effect of the choice of instrumentation on the quality of quantitative analyses as well as the effect of variable acquisition parameters. A series of exp eriments was designed in which samples were distributed to a number of workers using a range of FTIR instruments from different manufacturer s and of differing quality. The workers were allowed to use the access ory of their own choice and to carry out a quantitative analysis of gl ucose solutions using their normal operating parameters. In following experiments the effects of instrumental and purge were considered and quantitative analysis was performed using a set of prescribed acquisit ion conditions. The results showed that there were significant differe nces in the quality of the spectra produced on the different combinati ons. However, although each worker produced quite different linear cal ibrations (in terms of slope and intercept), they all predicted the co ncentration of an unknown with a similar accuracy. However,later exper iments showed that the low-cost bench-top instruments were not always so successful when the peaks used in the analysis were affected by res idual water vapour interferences. Instrumental drift was noticeably wo rse for the low-cost instruments but this was an effect that could eas ily be eliminated by suitable baseline correction.