P. Lecacheux et al., QUANTITATIVE-ANALYSIS OF CHOLESTEROL AND CHOLESTEROL ESTER MIXTURES USING NEAR-INFRARED FOURIER-TRANSFORM RAMAN-SPECTROSCOPY, Applied spectroscopy, 50(10), 1996, pp. 1253-1257
Near-infrared Fourier transform Raman spectroscopy is a rapid and nond
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 and esterified cholesterol in two
synthetic sample series. In 66 ternary mixtures containing various pro
portions of cholesterol, cholesterol linoleate, and oleate, the standa
rd errors of prediction were 1.27, 1.17, and 0.94%, respectively. For
the second series of experiments concerning the sensitive problem of q
uantitative analysis of cholesterol palmitate and stearate mixtures, t
he standard error of prediction for 49 samples was 3.02%. It is also p
ossible to extract quantitative information for a single component of
the ternary mixtures independently. These results are of great importa
nce when-as in the case of arterial samples-many chemical species are
present. Comparison between Raman spectra of ternary mixtures and athe
rosclerotic rabbit aorta shows that many bands, assignable to free and
esterified cholesterol, are easily observed in the aorta spectrum.