Solvent extraction/spectrophotometric determination of palladium(II) with 2N-(2-mercapto-4-chlorophenyl)-6-chloro-1, 2, 3-benzothiadiazoline

• Published in: BUNSEKI KAGAKU Vol. 40; no. 9; pp. 475 - 480
• Main Authors: WATANABE, Kunihiro, TAMURA, Kazuyoshi
• Format: Journal Article
• Language: Japanese
• Published: Tokyo The Japan Society for Analytical Chemistry 05.09.1991; Nippon Bunseki Kagakkai
• Subjects: 2; 2N-(2-mercapto-4-chlorophenyl)-6-chloro-1; solvent extraction; spectrophotometric determination of palladium
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.40.9_475

A specific reagent for the extraction/spectrophotometric determination of Pd(II), 2N-(2-mercapto-4-chlorophenyl)-6-chloro-1, 2, 3-benzothiadiazoline (Cl-MBTD) was synthesized. The reagent which contains sulfur as a donor atom behaves as a dibasic acid (H2R), and reacts with Pd(II) to form a complex, extracted over pH 1.92.6 into tributylphosphate (TBP). The complex in TBP showed maximum absorption at 793 nm. The acid dissociation constants of Cl-MBTD were pKa1=2.3 (H3R+ _??_ H2R), pKa2=11.1 (H2R _??_HR-), pKa3= 13.1 (HR- _??_ R2-), in 8% methanol solution at 25°C. The molar ratio of the complex extracted into the TBP phase was Pd : R: TBP=1 : 1: 2. The Pd complex extracted with Cl-MBTD obeyed Beer's law up to 30 μg. The molar absorption coefficient of the complex in TBP was 1.4×1041mol-1cm-1 at 793 nm. The effect of metal ions on the determination of Pd(II) with CI-MBTD was also studied in detail. Cr(VI) and Sn(IV) gave negative errors. This method was applied to the determination of Pd in alumina-based oxidative catalysts. The results agreed well with those obtained by AAS.