5-Methyl-furfral 2-Benzothiazolylhydrazone as Analytical Reagent -Application to the Extraction-Spectrophotometric Determination of Copper-

Abstract

5-Methyl-furfral 2-benzothiazolylhydrazone (MFBH) was synthesized by condensation of 5- methyl-furfral with 2-hydrazinobenzothiazole, and applied to the spectrophotometric determina- tion of copper. The acid dissociation constant of the reagent is determined spectrophotome- trically in 50% dioxane-water (v/v) at 25°C under an ionic strength of O.1 and found to be 10
Copper (II) forms 1: 2 complex with MFBH. The complex is soluble in benzene but insoluble in water. It has an absorption maximum at approximately 405--415 nm in benzene, and can be extracted quantitatively into benzene in the presence of pyridine. The extraction needs shaking more than 7 minutes.
The outline of the procedure is as follows; Take the sample solution containing less than 12 mg of copper (II) in a 50 ml separatory funnel, add 2 rra of 10% pyridine solution and an acetate buffer solution, and dilute to 30 ml with water (the solution is adjusted to pH 6.5). Add 10.0 ml of 2.0 x 10-4 mol/l MFBH solution in benzene and extract the complex by shaking the two phases for 10 minutes. Measure the absorbance of the extract at 410 nm against the reagent blank.
The calibration curve was linear in the range of 0 to 12 Aug copper (II) in benzene. The molar absorptivity and the sensitivity for log (41 I) =0.001 001 were 5.8x 1O^2- //molm and 1.1 x1O^2- Aug Cu/cm², respectively.
Silver ( I ), cobalt (IC), mercury 00, icon (111), thiocyanate and citrate interfered with the determination, but the other common ions did not interfere.