Tellurium was determined by introducing a solid membrane for the selective determination of tellurite ion. An electrode composed of a compressed disk containing a mixture of HgTeO 3 and Hg 2 Cl 2 was found to give a typical Nernstian response of 29 mV/concentration decade for the concentration range 10 05 to 10 01 M). The connection was made by Hg metal instead of aqueous inner filling. The optimum pH was 3.5-10.5. The selectivity of the electrode toward several inorganic and organic anions was estimated. The electrode was applied to the determination of tellurium in binary mixtures with a mean recovery of 98.99% and relative standard deviation range of 0.19-0.51%. α§ 1997 Academic Press Tellurium was determined by several methods including classical and instrumental analysis. Egikyan and Gaibakyan applied paper chromatography (1) or TLC (2) for separation and determination of Te in an acidic medium. Phenylhydrazinesulfinic acid (3) and morpholine-4-carbodithioate (4) were used as gravimetric reagents for Te determination. Dindi and Reddy (5) determined Te simply by adding a known excess of amonium cerium(IV) sulfate and titrating excess cerium against Fe(II). Also, tellurium in its alloys was analyzed by back-titration of the excess K 2 Cr 2 O 7 against Fe(II) using N-phenylanthranilic acid (6). Indirect compleximeteric titration was used to determine Te(IV) with diethyldithiocarbamic acid as reagent (7). Photometric titration of Te(IV) against K 2 Cr 2 O 7 at 380-430 nm was explained (8). Kobayashi and Imaizumi (9) used atomic absorption spectrometry to evaluate Te in urine by the hydride generation technique. Spectrophotometric analysis has been used widely for tellurium determination. Ishchenko et al. (10) analyzed Te spectrophotometrically at 360 nm after extracting (TeI 6 ) 20 hexadecylpyridinium complex into CHCl 3 . Rhodamine (11) and pyrrolidine-1-carbodithioic acid (12) were examined and used as sensitive spectrophotometric reagents for Te analysis.
Electrometric methods are commonly used in Te assay. Amperometric titrations with the use of either methyl thymol blue (13), permanganate ( 14), or dichromate (15) reagents have been found to be suitable for Te analysis. Hassan (16) determined tellurium in simple solution or binary mixtures by polarographic analysis. Also, trace determination of Te was achieved by the polarographic procedure (17,18). Agasyan et al. (19) used a coulometric method to determine TeO 20 3 in buffered solutions. Chavdarova and Sheitanov (20) used a coulometric titration with the aid of an electrolytically generated titanium. The test solution must be heated to 100ΠC and in a N atmosphere.
An ethanolic solution of 2-mercaptobenzoic acid was successfully used in a N atmosphere as a reagent for the potentiometric titration of tellurium with the aid of a