Quantitative analysis of entacapone isomers using surface-enhanced Raman spectroscopy and partial least squares regression
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Updated: May 16, 2026

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems
Published on: February 10, 2020
Marina Ratkaj1, Tomislav Biljan, Snežana Miljanić
1PLIVA Croatia, Teva Pharmaceutical Industries Ltd., Research and Development, Prilaz baruna Filipovića 29, HR-10000 Zagreb, Croatia. marina.ratkaj@pliva.com
Abstract:
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.
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