Masking of iron and other interferences during the spectrophotometric analysis of aluminum from soil samples using Alizarin Red S.

Abstract

In whole-rock geochemical analysis, the quantification of aluminum in geological samples is performed using different analytical techniques including UV-Vis spectrophotometry. During the spectrophotometric analysis of aluminum utilizing Alizarin Red S, iron causes significant interference, leading to inaccurate measurements of the amount of aluminum in the sample. In cases where leached or processed samples contain titanium, interference is also observed. However, appropriate masking agents can remove these interferences. In this study, various masking agents including Tiron, oxalic acid, ascorbic acid, and thioglycolic acid were utilized for the masking of iron. Among these masking agents, ascorbic acid proved to be the best candidate for masking iron. A simple and efficient method was then developed for the masking of iron with the optimization of parameters including concentration of ascorbic acid and reaction time. With this technique, 2 mL of ascorbic acid (10%) can mask iron at up to 3000 ppm in aliquots. Moreover, titanium interference is not observed with this method when the titanium concentration in the aliquot is below 100 ppm. This method was subsequently applied to geological samples and the results were compared to those of atomic absorption spectroscopy. Most samples can easily be analyzed for aluminum by utilizing this masking technique and circumventing interference problems.