Univariate and multivariate calibration strategies in combination with laser-induced breakdown spectroscopy (LIBS) to determine Ti on sunscreen: A different sample preparation procedure

Sunscreen is a cream which the intended use is to protect the human skin from ultraviolet radiation (UV) from the sun. Physical (inorganic) or chemical (organic) filters could be used to scatter the UV radiation, being TiO2, one physical filter widely used in its formulation. To determine Ti concentrations on sunscreen, laborious and unsafe procedures must be performed involving strong acids and high temperatures in furnaces. With laser-induced breakdown spectroscopy (LIBS) the possibility of determining this element with minimal sample preparation is feasible. In this study, Ti concentration on sunscreen was determined through several calibration approaches (univariate and multivariate) with LIBS and an unusual sample preparation for sunscreen using a solution of poly(vinyl)alcohol (PVA) to immobilize the sample, converting its matrix to solid. Five samples were prepared and analyzed by inductively coupled plasma optical emission spectrometry (ICP OES) and the Ti concentration ranged from 0.45 to 1.58%. Standard errors for cross validation (SECV) and recoveries were 0.07% and 97-104% using multiple linear regression (MLR) with information from two Ti emission lines: I 498.17 nm and I 499.11 nm.