Bottom-up and top-down measurement uncertainty evaluation for multivariate spectrophotometric procedures

Abstract

Multivariate spectrophotometric procedures are widely used in drug analysis to quantify one or more substances in a sample. Even if the analytical procedure is validated, there is always some degree of uncertainty related to the analytical results. No studies were found in the literature that evaluated the measurement uncertainty for multivariate spectrophotometric procedures. Thus, this paper aims to estimate the measurement uncertainty of the quantification of acetylsalicylic acid (ASA) and salicylic acid (SA), in an ASA samples, by a stability-indicating multivariate spectrophotometric procedure. The measurement uncertainties of ASA and SA were estimated by the top-down approach, using the Nordtest/ISO 11352 and VAM Project methodologies, and by the bottom-up approach, using the Monte Carlo method (MCM). The calculation of measurement uncertainty considered uncertainty sources related to the preparation of sample and standard solutions and the impact of these sources on the model obtained by partial least squares (PLS). The uncertainty of the spectra was estimated by bootstrap resampling method. The expanded uncertainties estimated for ASA were 3.7%, 4.1% and 3.7% calculated by MCM, Nordtest/ISO 11352 and VAM Project, respectively. The expanded uncertainties estimated for SA considering the concentration range from 2.67 to 6.67 μg/mL were 0.25, 0.36 and 0.35 μg/mL and for the concentration range from 6.67 to 18.67 μg/mL were 5.3%, 5.3% and 6.0% calculated by MCM, Nordtest/ISO 11352 respectively. It was concluded that the developed methodology allows to estimate the measurement uncertainty of a multivariate spectrophotometric analytical procedure by bottom-up and top-down approaches.