Direct Determination of the Aluminum Content in Antiperspirants Using Digital Image Colorimetry

Abstract

In this work a dilute‐and‐shoot procedure using digital image colorimetry (DIC) was evaluated for the determination of aluminum in antiperspirants. Derivatization was performed by means of the reaction between Al(III) and Alizarin Red S (ARS) reagent. Digital images were acquired using a table scanner and the average values for red, green and blue channels (RGB) were obtained. Optimal conditions were set at pH=4.5, ARS concentrations 10‐fold higher than Al(III) and using the G channel. The method presented linearity in the 2.0–10.0 mg L−1 range, the limit of detection (LOD) was 1.1 mg L−1 and precision was better than 2.55 %. Accuracy was checked by the analysis of spiked samples at 2.0 and 4.0 mg L−1 Al(III), and good recoveries (82.6–117.5 %) were obtained. Eight samples of roll‐on antiperspirants were analyzed by the proposed colorimetric method and the well‐stablished flame atomic absorption spectrometry (FAAS) comparative method. The obtained results were not statistically different at 95 % confidence level. An analytical greenness assessment was performed for both methods and the procedure based on digital image colorimetry was proven to be a greener approach due to miniaturization, low sample consumption, least amount of waste and high sample throughput.