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

• Published in: Journal of the Brazilian Chemical Society Vol. 17; no. 5; pp. 976 - 980
• Main Authors: Oliveira, Paulo C. C. de, Masini, Jorge C., Galhardo, Cristiane X., Lima, José C. de S., Sant'ana, Antonio E. G., Vasconcelos, Ana M. G., Nunes, Wanessa P., Amaral, Osvaldo L. C.
• Format: Journal Article
• Language: English
• Published: Sociedade Brasileira de Química 01-10-2006
• Subjects: CHEMISTRY, MULTIDISCIPLINARY; flow injection analysis; gas-diffusion device; bicarbonate ions
• ISSN: 0103-5053; 1678-4790
• DOI: 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.