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A new approach to construct diffusion/permeation cell for use in flow systems: application in the spectrophotometric determination of bicarbonate ions

2006; Brazilian Chemical Society; Volume: 17; Issue: 5 Linguagem: Inglês

10.1590/s0103-50532006000500023

1678-4790

Paulo César Costa de Oliveira, Jorge C. Masini, Cristiane Xavier Galhardo, José C. de S. Lima, Antônio Euzébio Goulart Santana, Ana M. G. Vasconcelos, Wanessa P. Nunes, Osvaldo L. C. Amaral,

Environmental Chemistry and Analysis

This work describes a new approach for construction of gaseous diffusion/permeation module in a configuration based on the perfect fitting between two plaques of acrylic. It was employed to determine bicarbonate ions exploiting the discoloration of a 0.01% (m/v) phenolphthalein solution in medium of 1.0 x 10-5 mol L-1 NaOH (pH 9.0). The variation in the indicator color was monitored at 552 nm. The analytical curve showed a working range between 25.0 and 150.0 mg L-1 in NaHCO3. Consecutive injections (n=10) of a standard 5.0 mg L-1 NaHCO3 solutions exhibited less than 1.0% of relative standard deviation. The correlation coefficient of analytical curve was 0.9996 and the limit of detection (3 x noise/slope) is 4.41 mg L-1 in NaHCO3. The proposed method is rapid (50 sample/hour) and results were in good agreement with the ones obtained by classical titrimetry.