Investigation of applicability of a mid-infrared spectroscopic method using an attenuated total reflection accessory and a new near-infrared transmission method for determination of faecal fat

Abstract

SUMMARY. In many laboratories, the titrimetric method of Van de Kamer is used for the analysis of faecal fat content of patients suspected of steatorrhoea. We investigated the applicability of a mid-infrared (MIR) spectroscopic method, using an attenuated total re¯ection (ATR) accessory, and a new near-infrared (NIR) spectroscopic method. For the NIR method, sealed plastic bags containing the stool samples were used as transmission cells. Standardization was obtained using a previously described MIR method, with a NaCl¯ow-cell, as reference method. Partial least-squares regression was used for the calibration of each method. Full cross-validation of the calibration set was used for the internal validation of each method. Fifteen per cent of the stool samples could not be estimated with the ATR method within reasonable accuracy limits compared with the reference. The standard error of prediction of the NIR method was 1´1 g/dL. We conclude that the new NIR method is a promising technique for routine use. However, further experiments need to be done with triplicate measurements of each sample and the use of an external validation set.

Multivariate Prediction of the Thermal-Induced Weak Interaction Changes of Poly(N-Isopropylacrylamide) Film by the Interconversion between Middle and Near-Infrared Spectra

“…In recent years, the combined use of NIR and MIR spectra has gained popularity in a wide variety of applications, especially in macromolecules and biomolecules, to effectively deal with the complexity of NIR spectral bands. [1][2][3][4] Multivariate methods are often necessary for the analysis, calibration, and band assignments of the corresponding NIR spectra. Several approaches, including partial least squares (PLS), 5,6 principal component regression (PCR), 7 and principal component analysis (PCA), 8 have been tried with varying degrees of success.…”