Determination of glucose in dried serum samples by Fourier-transform infrared spectroscopy.

BACKGROUND Practical improvements are needed to allow measurement of glucose concentrations by Fourier- transform infrared (FT-IR) spectroscopy. We developed a new method that allows determination of the glucose concentration in dried sera. METHODS We studied 32 serum samples after fourfold dilution and desiccation before FT-IR analyses on a spectrometer operated at a resolution of 2.0 cm(-1). We integrated all spectral windows at the surface of the spectrum in the C--O region. For comparison, glucose was measured in the sera by a glucose oxidase method. RESULTS One peak within the spectrum was most specific for glucose (997-1062 cm(-1)). Its surface integration showed a strong relationship with reference data (r = 0.998; P <0.001). FT-IR analyses of five glucose solutions were performed to determine its specific absorption at the same peak. In this way, glucose concentrations in serum spectra could be measured. For the first time while using FT-IR spectroscopy, no manipulation of spectra nor use of internal standard was necessary to obtain results in high accordance with glucose concentration measured by a conventional (glucose-oxidase) method (S(y|x) = 0.25 mmol/L; r = 0. 998). CONCLUSIONS FT-IR spectroscopy appears to be an easy and accurate method to determine glucose concentration and could be widely used to simultaneously identify and quantify several metabolites in biological fluids or tissues.