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Quantitative analysis of entacapone isomers using surface-enhanced Raman spectroscopy and partial least squares regression

Surface-enhanced Raman spectroscopy (SERS) and partial least squares (PLS) regression have been applied for quantification of entacapone isomers E and Z in solution. Nine mixtures of isomers Z and E in ethanol ranging from 0% and 100% w/w were analyzed, for a total entacapone concentration of 1 x 10E-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 x 10E-5 mol L-1 of isomer Z in solution.

surface-enhanced Raman spectroscopy; entacapone; partial least squares regression; quantification; Klarite

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