Spectrophotometric determination of cerium(IV) with tetraethylenepentaamineheptaacetic acid (TPHA)

Tetraethylenepentaamineheptaacetic acid (TPHA) combines with cerium(IV) to form an intensely yellow chelate having a molar absorptivity of 4.5 × 10⁴ mol⁻¹ · cm⁻¹ · liter at 304 nm. The chelate contains 1 mol of TPHA coordinated to a cerium(IV) atom. Beer's law is followed from 0.05 to 0.5 ppm cerium (1.00-cm cells). Of many ions tested at the 1-ppm level and the 100-ppm concentration, only iron(III) produces little interference.     

Rapid extraction and spectrophotometric determination of vanadium(IV) with thiothenoyltrifluoroacetone

Thiothenoyltrifluoroacetone in carbon tetrachloride-butanol (1:1) is used for extraction and spectrophotometric determination of vanadium (IV) at pH 4.5-5. The greenish-yellow complex is measured spectrophotometrically at 450 nm. The system conforms to Beer's law over the range 2-11 mug/ml of extract. The colour of the complex is stable for at least 80 hr. Vanadium (IV) was quantitatively extracted and determined in the presence of 120:1 w/w ratios of various ions. The method was made selective by using common sequestering agents or prior extraction with tributyl phosphate, diethylammonium diethyldithiocarbamate, alpha-furildioxime or acetylacetone. The method is rapid, simple, selective and sensitive.     

Rapid and sensitive spectrophotometric determination of cerium(IV) with 2,4-dihydroxy benzophenone benzoic hydrazone

A simple and sensitive spectrophotometric method for the determination of cerium(IV) in an aqueous medium is reported. The metal ion formed a 1:1 orange-red coloured complex with 2,4-dihydroxy benzophenone benzoic hydrazone (DHBPBH) at pH 10.0 showing an absorption maximum at 400 nm. The molar absorptivity and Sandell's sensitivity of the method are found to be 2.0 x 10(4)1/mol/cm and 0.007 mug/cm(2), respectively. Beer's law is obeyed in the range 0.7-7.0 mug/ml. Titanium, vanadium and molybdenum do not interfere. The extent of interferences by other ions is presented. The method is applied for the determination of cerium in simulated rock samples.     

Indirect spectrophotometric determination of cerium(IV)

A simple and very fast photometric method for the determination of trace levels of cerium(IV) has been developed. Use has been made of the reaction in which iron (II), on oxidation with cerium(IV), gives iron(III) which is complexed with tiron, in acidic medium, to form a stable blue color, the intensity of which is in direct proportion to the amount of cerium(IV) originally present in the sample solution. In addition, the method has a wide range of determination and reasonable sensitivity, and it avoids both temperature control and the tedious extraction step.     

Solvent extraction and photometric determination of a microgram of cerium with N-p-tolyl-p-chlorobenzohydroxamic acid

A spectrophotometric method for determination of a microgram quantity of cerium with N-p-tolyl-p-chlorobenzohydroxamic acid is described. The orange-red-colored complex is extracted from chloroform at pH 9 which absorbs between 460 and 465 nm. Beer's law is obeyed at this wavelength. A clean-cut separation from many commonly occurring metal ions is easily accomplished. The system obeys Beer's law within the range of 0.5–28 ppm of cerium(IV). The molar absorptivity of cerium-N-p-tolyl-p-chlorobenzohydroxamic acid complex is 4.5 × 10³ liters mol^?1 cm^?1.     

Spectrofluorimetric determination of pharmaceutical compounds with the cerium(IV)—cerium(III) system

The compounds to be determined are oxidised by cerium(IV). The concentration of cerium(III) formed is measured spectrofluorimetrically. The method has been used both in solution and, by fluorodensitometry, on t.l.c. plates. Detection limits of some substances are 15 ng ml^-1 for the solution method and 5 ng per spot for the t.l.c. method.     

Separation and gravimetric determination of thorium and cerium(IV) with vanillin

Vanillin forms insoluble complexes with thorium and cerium(IV) at pH 4.0–6.2 and 2.5–7.0 respectively. Thorium and cerium can be determined gravimetrically and separated from each other as well as from uranium(VI) and typical trivalent rare earths. The precipitates obtained are ignited to the corresponding oxide and weighed; as little as 4.4 mg of ThO₂ and 4.9 mg of CeO₂ can be determined.     

Rapid photometric determination of neptunium with xylenol orange after extraction with Aliquat-336

A rapid method based on the extraction of neptunium(IV) by Aliquat-336 followed by its direct photometric determination in the organic phase employing xylenol orange is reported. Optinum conditions have been established for the extraction and determination of as little as 0.4 ppm of Np. The molar absorptivity of the red-coloured neptunium complex at 535 nm is 49535±361 1·mol⁻¹·cm⁻¹. Unlike the well-known absorptimetric method for estimating NP(IV) with Arsenazo III, this method tolerates many-fold excesses of fluoride, nitrite, nitrate, phosphote, oxalate as well as UO ₂ ²⁺ , Pu⁴⁺, Zr⁴⁺, etc., which are some of the major contaminants associated with neptunium during its reprocessing.     

Simultaneous spectrofluorimetric determination of cerium(III) and cerium(IV) by flow injection analysis

Cerium(III) (1–100 μg l^?1) is determined by injection into a carrier stream of hydrochloric, perchloric or sulphuric acid, and monitoring its native fluorescence. Cerium(IV) can be determined similarly by incorporating a zinc reductor minicolumn into the system. Splitting the injection sample so that only part passes through the reductor, and the remainder by-passes it, allows total cerium and cerium(III) to be detected from the two sequential fluorescence peaks obtained.     

Solvent extraction and photometric determination of molybdenum (VI) with 2-aminobenzenethiol

A new extractive photometric method is described for estimation of molybdenum with 2-aminobenzenethiol. The green complex in chloroform has its absorbance maximum at 700 nm and is stable for 2 hr when extracted from a solution of optimum pH range 1.4-2.8. The extraction is quantitative. The sensitivity is 0.0075 microg cm (2). Beer's law is obeyed over the range 0.25-10 ppm with optimum range 0.5-4.5 ppm. The molar absorptivity is 7.08 x 10(4) 1.mole(-1). cm(-1). The overall stability constant is 2.0 x 10(8) at 25 +/- 0.1 degrees.     

Protonation and solvent extraction of N-p-tolylbenzohydroxamic acid in hydrochloric acid medium

the protonation of N-p-tolylbenzohydroxamic acid (p-TBHA) in aqueous hydrochloric acid has been investigated by determination of its distribution between cyclohexane and hydrochloric acid. The pK(a) value found was - 2.30 +/- 0.02 at 30 degrees . The solubility of p-TBHA as a function of hydrochloric acid concentration has also been determined. At lower acid concentrations the solubility decreases owing to a salting-out effect, whereas at higher concentrations it increases because of formation of the more hydrophilic protonated species and a salting-in effect. Intramolecular hydrogen-bonding observed in p-TBHA provides evidence for protonation of the nitrogen atom.     

Extractive photometric determination of plutonium(IV) with Aliquat-336 and xylenol orange

A rapid extractive photometric method using Aliquat-336 and xylenol organe for the determination of plutonium(IV) at μg levels has been developed. Quantitative extraction is obtained from ∼4M aqueous HNO₃ medium, affording estimation in the presence of several commonly occurring impurities, viz. iron, uranium, fission products and cladding materials. Effects of acidity, reagent concentration and diverse ions on the estimation have also been invetigated. Unlike the well-known absorptiometric method for determining plutonium(IV) employing Arsenazo III, the procedure presented here tolerates manyfold excesses of uranium(VI) as well as chromium(III), iron(III) and zirconium(IV), which are some of the major contaminants of plutonium during reprocessing.     

Extractive separation and photometric determination of neptunium(IV) and plutonium(IV) from their mixtures

A rapid and sensitive method for the photometric determination of trace amounts of neptunium and plutonium from their mixtures is described. Np(IV) is selectively extracted from about 1 M HNO₃ medium with TTA in xylene retaining Pu in the nonextractable trivalent state in the aq. phase with ferrous sulfamate. Plutonium in the aqueous phase is subsequently oxidized with NaNO₂ to the highly extractable tetravalent state and extracted with TTA. Np(IV) as well as Pu(IV) thus extracted are finally estimated in the organic phase itself spectrophotometrically employing xylenol orange as the chromogenic reagent. Their molar absorptivities are in the 5 × 10⁴ range. Beer's law is valid up to 2.4 ppm Np and 3.5 ppm Pu. The color of the solutions is stable for at least 48 hr. The method tolerates large excess of several common contaminants encountered during spent fuel reprocessing. Cerium(IV) and phosphoric acid, however, interfere with the final estimation.