Definition of QC Parameters for the Practical Use of FTIR-ATR Spectroscopy in the Analysis of Surface Treatment of Cork Stoppers

Abstract The aim of this investigation has been to define universal parameters that could be extracted in a straightforward way from FTIR-ATR spectra for the quality control (QC) of cork stoppers for paraffin and silicone; i.e., the most common components in surface treatment for lubrication and sealing. Three indicators, namely TC (total coating), SC (silicone coating), and PC (paraffin coating), are proposed, which are readily obtained from ratios of absorbances of some characteristic bands due to cork, paraffin, and silicone. These indicators are deduced with a minimum of approximations, they are solely connected with the amount of the species on the surface, and do not depend on the instrument used for the analysis. The validity of the methodology proposed has been tested with cases coming from real life, being applicable to natural cork stoppers, 1+1 and agglomerate types. Some guidelines are also provided for its application in case of colmated stoppers. Finally, other approaches that may take advantage of the readiness and non-invasive features of FTIR-ATR spectroscopy are discussed.

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