Surface-enhanced Raman spectroscopy (SERS) and partial least squares (PLS) regression have been applied for the quantification of entacapone isomers E and Z in solution. Nine mixtures of isomers Z and E in ethanol ranging from 0% to 100% w/w were analyzed, for a total entacapone concentration of 1 × 10−3 mol L−1. Upon deposition onto commercially available Klarite® gold plates, highly intense and reproducible SERS spectra were obtained from the entacapone isomers. Based on the spectral measurements, a two-component PLS model for correlation of predicted and real content of the isomers mixtures was developed. Root-mean-square error of the predicted composition was found to be 8% of isomer Z in the isomers mixture, corresponding to the absolute concentration of 8 × 10−5 mol L−1 of isomer Z in solution.
Vol. 8, Iss. 1 Virtual Journal for Biomedical Optics
Marina Ratkaj, Tomislav Biljan, and Snežana Miljanić, "Quantitative Analysis of Entacapone Isomers Using Surface-Enhanced Raman Spectroscopy and Partial Least Squares Regression," Appl. Spectrosc. 66, 1468-1474 (2012)