Peak window correlation method for drug screening using Raman spectroscopy

Modern portable and hand-held Raman spectrometers that recently have become widespread in drug quality screening have good reproducibility and are able to detect small concentrations of substances in mixtures of several components or distinguish compounds similar in structure and having minimal differences in spectrum with appropriate mathematical processing methods. Among other spectrum comparison approaches, the peak search at their location is the most important task of spectral imaging of the studied samples. In this work, the Raman spectra of liquid drugs involved in the governmental non-destructive quality screening program performed by 8 mobile laboratories equipped with Raman spectrometers with uncooled detector and a 532 nm laser were compared with reference sample spectra using the peak windows correlation (PWC) algorithm developed in this work by authors. The proposed method provides accurate identification, detection of composition changes, and presence of foreign components in drugs formulations even if their contribution to the overall signal is negligible. The spectral correlation method called hit-quality index (HQI) method conventionally used for such portable spectrometers was specified as comparative method.