Study of Pharmaceutical Samples using Optical Emission Spectroscopy and Microscopy

The growth of the pharmaceutical industry to keep pace with the well-being of humans worldwide has posed many challenges related to quality control. This paper reports on the potential application of a modern optical spectroscopic technique popularly known as laser-induced breakdown spectroscopy (LIBS) to address some quality aspects such as the sample constituents, hardness, and classification of five different pharmaceutical samples. The surface analysis of these samples has been carried out using optical microscopy (OM) and atomic force microscopy (AFM). The LIBS spectra of different pharmaceutical samples of different brands have been recorded in air at atmospheric pressure using a high-energy Nd:YAG laser and an echelle spectrometer coupled with an intensified charge-coupled device camera. The LIBS spectrum provides the spectral signatures of lighter elements like carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and the CN violet band, along with inorganic elements like calcium (Ca), magnesium (Mg), etc. Two different multivariate analysis methods, principal component analysis (PCA) and artificial neural network (ANN), have been employed with the LIBS spectral data matrix to obtain the classification of these samples. OM and AFM were used to investigate the surface quality of the tablets, which helps the pharmaceutical industry in increasing the life of pharmaceutical products. The LIBS-based hardness of the sample matrices is estimated, and a correlation has been established with AFM-based RMS roughness. The results illustrate the strength of the LIBS coupled with multivariate analysis like PCA and ANN for a rapid and reliable analysis of pharmaceutical products. Also, LIBS coupled with OM and AFM might be an effective way to address surface quality aspects of pharmaceutical samples.