Validation of an analytical methodology to determine humic substances using low-volume toxic reagents

Abstract

Abstract The 12 principles of green chemistry were stated to pursue good practices and techniques that minimize the use of hazardous substances in the production and application of chemicals. To minimize the risks and the pollution generated using chemicals, new methodologies must be developed that avoid the application of dangerous products or its amount. Considering the principle of pollution prevention, this work proposes the development and application of a different methodology for the quantification of humic substances (HS), applying a spectrophotometric methodology that reduces the quantity of hazardous reagents (sodium dichromate and sulfuric acid) and minimizes the waste production. To deeply acknowledge the method, a validation of the methodology was done to allow the evaluation of its effectiveness to report reliable results. It was done by the evaluation of the parameters often used for this purpose (analytical limits, precision, accuracy, selectivity, robustness, and method working range). The detection limit attained was 0.03 g glucose/L and the quantification limit was 0.09 g glucose/L. The precision and accuracy were also evaluated using the repeatability limit and through performance testing, respectively, with a repeatability limit of 0.045 g/L and a Z-score less than 2. For selectivity and robustness, differences in variances were not significant, and the working range is well adjusted, with no differences regarding the precision of the lower and higher standard. The results obtained showed that the method under study, adapted to the green chemistry principles, can be applied to quantify HS in impure and complex samples.