Near infrared reflectance spectroscopy for the fast identification of PVC-based films

Near infrared (NIR) reflectance spectroscopy was used to develop a non-dest ructive and rapid qualitative method for the analysis of plastic films used by the pharmaceutical industry for blistering. Three types of films were i nvestigated: 250 mum PVC [poly(vinyl chloride)] films, 250 mum PVC films co ated with 40 g m(-2) of PVDC [poly(vinylidene dichloride)] and 250 mum PVC films coated with 5 g m(-2) of TE (Thermoelast) and 90 g m(-2) of PVDC. Thr ee analyses were carried out using different pre-treatment options and a PL S (partial least squares) algorithm. Each analysis was aimed at identifying one type of film and rejecting all types of false sample (different thickn ess, colour or layer). True and false samples from four plastics manufactur ers were included in the calibration sets in order to obtain robust methods that were suitable regardless of the supplier. Specificity was demonstrate d by testing validation sets against the methods. The tests showed 0% of ty pe I (false negative identification) and 1% of type II errors (false positi ve identification) for the PVC method, 13 and 3%, respectively, for the PVC -PVDC method and no error for the PVC-TE-PVDC method. Type II errors, mostl y due to the slight sensitivity of the methods to film thickness, are easil y corrected by simple thickness measurements. This study demonstrates that NIR spectroscopy is an excellent tool for the identification of PVC-based f ilms. The three methods can be used by the pharmaceutical industry or plast ics manufacturers for the quality control of films used in blister packagin g.