Near-infrared spectra of serum albumin and gamma-globulin and determination of their concentrations in phosphate buffer solutions by partial least squares regression

Near-infrared (NIR) spectra have been measured for albumin and gamma-globul in in a powder state as well as in phosphate buffer solutions. The second d erivative spectra of powder samples have been used to make assignments of N IR bands of the proteins. The second derivative spectra of albumin and gamm a-globulin are significantly different from each other in the band frequenc ies and relative intensities. The NIR spectra in the 1300-1850 mt region of the solutions have been subjected to partial least squares (PLS) regressio n analysis to develop chemometrics models which predict the concentrations of the proteins. The calibration for the albumin solutions in the concentra tion range of 0.1-8.0 g/dl has yielded a correlation coefficient (R) of 0.9 995 and a standard error of calibration (SEC) of 0.207 g/dl. For the gamma- globulin solutions in the concentration range of 0.1-6.0 g/dl, R of 0.9946 and SEC of 0.128 g/dl have been obtained. Regression coefficients (RCs) for the calibration models have been calculated for the first four factors. Th ese RCs reflect the spectral variations in bands due to the proteins and in a water band near 1400 nm caused by the dissolution of the proteins. Moreo ver, the RCs have been compared with the NIR spectra of the proteins in the powder state. The positions of peaks in the RCs correspond well to those o f bands in the NIR spectra of the proteins in the powder state. This sugges ts that the chemometrics models can pick up effectively the information abo ut albumin and gamma-globulin, even if the models have been constructed fro m the spectra of the proteins in the dilute solutions. (C) 1998 Elsevier Sc ience B.V. All rights reserved.