GLUCOSE DETERMINATION IN SIMULATED BLOOD-SERUM SOLUTIONS BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY - INVESTIGATION OF SPECTRAL INTERFERENCES

Determination of physiological concentrations of glucose in whole bloo d or blood serum using infrared (IR) spectrometry is complicated due t o combined effects of spectral variations caused by fluctuations in te mperature, pH and other blood constituents with overlapping spectra. I n order to initiate systematic examination of these effects, we studie d the effects of temperature and pH changes on the spectral variation of phosphate buffered saline (PBS) solutions and glucose doped PBS sol utions in vitro. We observed that temperature and pH variations in the glucose doped PBS solutions cause significant changes in absorbance r ecorded with a Fourier transform infrared/attenuated total reflectance apparatus in the spectral region which contains information about glu cose. Primary blood constituents which may interfere with the IR spect rophotometric measurement of glucose in serum were identified. Blood s erum solutions were simulated by mixing glucose and the primary interf ering constituents in their physiological concentrations with PBS. The feasibility of accurate prediction of physiological glucose concentra tion in simulated serum solutions covering physiological variations of blood constituents was assessed by applying univariate techniques, mu ltivariate statistical methods and artificial neural networks (ANN) to their mid-IR spectra. Multivariate methods based on partial least squ ares, principal component regression and ANN produced calibration mode ls with smaller standard errors of prediction (SEP) of 16.9, 18.8 and 18.8 mg dl-1, respectively, compared with univariate methods based on peak height and area determinations which yield a smallest SEP of 40.1 mg dl-1. We conclude that in spite of physiological variations of maj or interfering constituents, physiological glucose concentration in aq ueous multicomponent mixtures such as blood serum may be predicted wit h sufficient accuracy for clinical applications using multivariate che mometric techniques.