Determinação de cromo (VI) por espectrometria de absorção atômica com chama após a extraçã o e pré-concentração no ponto nuvem

Abstract

The present work reports a method for chromium (VI) determination by flame atomic absorption spectrometry (FAAS) after cloud point extraction and preconcentration. Chromium (VI) is complexed with 1,5-diphenylcarbazide (DFC) in acidic medium (pH 2.0) and it is extracted into 25 μL of surfactant-rich phase containing Triton X-114. The variables that affect the cloud point formation, such as the surfactant (0.1-1.0% m/v) and complexant (0.01-0.80% m/v) concentrations, time of complexation (0-60 min), and effect of electrolyte NaCl (0-20% m/v) addition are evaluated. Under optimized conditions, 0.3% m/v Triton X-114, 0.05% m/v DFC and 10% m/v NaCl are used for chromium (VI) extraction. This method allows detection and quantification limits of 0.4 μg L -1 and 1.5 μg L-1, respectively, and a linear calibration range from 5 to 500 μg L-1. The preconcentration factor obtained is 27 and the extraction efficiency achieved varies from 87 to 99.3%.