Carbon dioxide spectrophotometric determination in whole roasted coffee beans using a total analysis system after super-modified simplex optimization

Abstract

In this work an automated methodology for the spectrophotometric determination of carbon dioxide in whole roasted coffee beans was developed. The analytical flow system was based on a reaction vessel featuring a lab-made gas diffusion flow cell. The coffee beans, without any pre-treatment, were poured in a vessel into which an acidic solution was added to promote carbon dioxide evolution from the sample. By pervaporation, the gas was thereafter trapped in a gas diffusion flow cell containing an acceptor solution which was afterwards analyzed by spectrophotometry. To enhance the sensitivity of the methodology, an experimental design based on super-modified simplex method was carried out to adjust the chemical composition of the acceptor solution. The developed methodology showed to be suitable to determine carbon dioxide in roasted coffee samples, and present as main advantages a higher determination rate (ca. 7 h−1) and reduced labor comparing with usually followed methodologies. Under the selected experimental conditions, the minimum quantity of carbon dioxide detected was of 4.62 × 10−7 mol. The results obtained by the developed methodology were correlated with those provided by the Hinman methodology.