QUANTITATIVE-DETERMINATION OF FREE AND ESTERIFIED CHOLESTEROL CONCENTRATIONS IN CHOLESTEROL-FED RABBIT AORTA USING NEAR-INFRARED FOURIER-TRANSFORM RAMAN-SPECTROSCOPY

Near-infrand-Fourier transform-Raman spectroscopy is a rapid and non-d estructive technique that can provide reliable qualitative in situ inf ormation about the chemistry of biological samples. We have combined t his technique with partial least squares (PLS) regression to perform a quantitative determination of free cholesterol and cholesterol esters in two synthetic sample series, in order to evaluate the performance and accuracy of the Raman-PLS method. In 65 ternary mixtures containin g various proportions of cholesterol, cholesterol linoleate and oleate , the standard errors of prediction (SEP) are 1.3%, 1.2% and 0.9%, res pectively. In the case of these ternary mixtures, it is also possible to extract quantitative information for a single component independent ly. For the second series of experiments, concerning the delicate prob lem of quantitative analysis of cholesterol palmitate and stearate mix tures, the standard error of prediction for 49 samples is 3.0%. After this preliminary study, the technique was used for the quantitative an alysis of free and esterified cholesterol in rabbit arterial wall. Com paring the Raman-PLS results with the biochem!cal results, the SEP are 0.24 mg g(-1) of tissue in 31 rabbit aorta samples for free cholester ol and 0.35 mg g(-1) of tissue in 30 samples for esterified cholestero l. Using the Raman-PLS method, quantitative analysis is performed in a pproximately 10 min without destruction of the samples.