T.V. Ramakrishna

Spectrophotometric determination of mercury(II) as the ternary complex with rhodamine 6g and iodide

Abstract The formation of a pink-coloured product when rhodamine 6G is treated with tetraiodomercurate(II) is used to determine mercury (5–25 μg) in a final volume of 25 ml. The reaction occurs immediately over the pH range 1–7 and, when the system is stabilized with gelatin, the absorbance remains unchanged at 575 nm for at least 24 h. The few interfering ions can be masked by the addition of appropriate reagent solutions. The method is simple and reliable and provides a molar absorptivity of 7.0·10 4 l mole -1 cm -1 .

Spectrophotometric determination of uranium with anthranilic acid and rhodamine 6G

The reaction of the uranium-anthranilic acid complex to form an ion-association complex with Rhodamine 6G provides a means for its estimation. The anionic primary complex is suggested to be a mixed-ligand complex of uranium with anthranilic acid and its oxidation products. The method is sensitive ( = 6.25 x 10(4) 1.mole(-1).cm(-1) at 575 nm) and fairly selective, and obeys Beers law for 0.04-4.00 ppm of uranium. It has been applied to analysis of monazite sand.

A chemical enhancement method for the spectrophotometric determination of trace amounts of arsenic.

A highly sensitive spectrophotometric method for the determination of 0.03-1.0 microg of arsenic is described. After extraction as AsI(3) into benzene, it is selectively stripped into water. Both the arsenic(III) and iodide present in the aqueous phase are made to react with iodate in acidic medium in the presence of chloride to form the anionic chloro complex, ICl(-)(2). The determination is completed after extraction of ICl(-)(2) species as an ion-pair with Rhodamine 6G into benzene and measuring the absorption of the extract at 535 nm. The coefficient of variation is 1.5% for 10 determinations of 0.5 microg of arsenic. The method has been applied to the determination of arsenic content in plant materials, high purity iron, copper base alloys and inorganic arsenic levels of natural waters.

Spectrophotometric determination of thallium after its extraction as an ion-pair of the chloro-complex and pyronine G

A sensitive and selective procedure for the spectrophotometric determination of thallium is described. The method is based on the formation of an ion-pair between [TlCl(4)](-) and the pyronine G cation in chloride-containing acid media. The ion-pair is extracted into benzene and permits the determination of as low as 0.3 mug of thallium in a final volume of 25 ml at 530 nm. The system obeys Beers law in the concentration range 1-14 mug of thallium in a final volume of 25 ml. Potassium iodate was found to be highly effective for the oxidation of Tl(I) to Tl(III) and the presence of excess oxidant does not interfere. The method can be used for the determination of thallium in high purity cadmium, cadmium sponge and rock samples.

Fluorimetric determination of trace quantities of mercury as an ion-association complex with rhodamine 6G in the presence of iodide

A procedure for the indirect fluorimetric determination of mercury(II) is described, based on selective extraction of the ion-association complex formed between triiodomercurate(II) and Rhodamine 6G and subsequent release of the fluorescent Rhodamine 6G. The calibration curve is linear up to 1 ppm of mercury(II). The few interferences are easily overcome.

Selective extractive separation of zinc, cadmium and lead from iodide media with mesityl oxide.

The extractive separation of zinc, cadmium and lead with mesityl oxide has been investigated as a function of iodide concentration and acidity. The recovery of these metals from the organic phase by back-extraction and the behaviour of other elements under the optimal conditions established for each metal ion have been examined. The method developed has been applied to the separation of these metals from rock samples before determination by spectrophotometry.

Spectrophotometric determination of osmium with 1,5-diphenylcarbazide.

The formation of the bluish violet osmium-diphenylcarbazide complex in weakly acidic solution is utilized for the determination of osmium by spectrophotometry. When measurements are made at 560 nm, after extraction of the complex into isobutyl methyl ketone, Beers law is obeyed up to 150 mug of osmium. Relatively few ions interfere, and these can be masked with EDTA and fluoride.

Chemical enhancement method for the determination of mercury by spectrophotometry after iodide extraction

A selective and sensitive spectrophotometric method for the determination of 0.08-2.5 ppb of mercury(II) is described. Mercury is extracted as tetraiodomercury(II)-Cd-phenanthroline ion-pair into benzene and selectively stripped into EDTA. The iodide associated with mercury present in the stripping is oxidized to iodate and then treated with excess iodide to give iodine. The iodine formed is extracted into benzene and equilibrated with iodate in acidic medium in the presence of chloride and Rhodamine 6G for the formation of ICI(-)(2) species and its extraction as ion-pair with Rhodamine 6G. Determination is completed by measuring the absorption of the extract at 535 nm. The coefficient of variation is 1.5% for 10 determinations of 200 ng of mercury. The method has been applied to establish the mercury content of natural waters and chloralkali plant effluent.

Spectrophotometric determination of traces of lead with bromopyrogallol red and cetyltrimethylammonium or cetylpyridinium bromide

A method is described based on the sensitizing effect of cetyltrimethylammonium or cetylpyridinium bromide on the lead-Bromopyrogallol Red colour reaction. The reaction is instantaneous and the colour remains stable for over 120 hr in the presence of Triton X-100. Both colour systems obey Beers law up to 5.5 ppm of lead. Methods are described for dealing with interferences.

Spectrophotometric determination of tellurium in trace quantities by use of an ion-association complex.

The formation of an ion-association complex by the interaction of iodotellurate(IV) with cetyltrimethylammonium bromide is used as the basis of an extractive procedure to determine tellurium in the range 2.5-12.5 mug in a final aqueous phase volume of 20 ml. The method is simple, reliable and sensitive. Selectivity is achieved by separation of tellurium on aluminium hydroxide as collector.