Resumen

OLIVEIRA, Paulo C. C. de et al. A new approach to construct diffusion/permeation cell for use in flow systems: application in the spectrophotometric determination of bicarbonate ions. J. Braz. Chem. Soc. [online]. 2006, vol.17, n.5, pp. 976-980. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532006000500023.

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.

Palabras llave : gas-diffusion device; flow injection analysis; bicarbonate ions.