Extractive spectrophotometric determination of palladium(II) in dental alloys with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine and tetrabromophenolphthalein ethylester.

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A sensitive spectrophotometric method for the determination of Pd(II) in dental alloys is proposed. It is based on the reaction of 3-(2-pyridyl)-5, 6-diphenyl-1, 2, 4-triazine (PDT) and Pd(II) and on the formation of a 1:1 ion associate with tetrabromophenolphthalein ethylester (TBPE) which is extractable into 1, 2-dichloroethane at pH 56. A required amount of the dental alloy sample (0.10.5 g) was dissolved in 5 ml of concentrated nitric acid by heating and the resulting solution was evaporated to dryness. The residue was dissolved again in 5 ml of 1 M hydrochloric acid by heating. The solution was filtered, and the filtrate was diluted to 100 ml with 1 M hydrochloric acid. A sample solution containing up to 10 μg of Pd was transferred into a 50 ml-volumetric flask. To it, 1 ml of 5 × 10-3 M PDT solution, 2 ml of 3 × 10-3 M TBPE solution and 15 ml of buffer solution (pH 5.5) were added and the mixture was diluted to 50 ml with distilled water. After standing for 10 min, the solution was transferred into separatory funnel. It was shaken with 10 ml of 1, 2-dichloroethane for 10 min. After the organic phase was centrifuged to remove droplets of water, absorbance of the organic phase was measured at 610 nm against the reagent blank. The calibration curve was linear over the range 20200 ppb of Pd(II) and the apparent molar absorptivity was 10.8 × 104 1 mol-1 cm-1; Sandell sensitivity, 0.00098 μg cm-2; and the standard deviation, 1.5%. Although Co(II), Fe(II), Cu(II), Rh(III) and Ru(II) interfered with the determination of Pd(II) in the general procedure, these interferences could be reduced by adding appropriate masking agents.