Rapid spectrophotometric determination of cerium(IV), arsenic(III), and nitrite with perphenazine

Perphenazine dihydrochloride, PPN, is proposed as a new reagent for the spectrophotometric determination of cerium(IV), arsenic(III), and nitrite. The reagent forms a red-colored species with cerium(IV) instantaneously in 3.5–5.5 M phosphoric acid medium. The red species exhibits maximum absorbance at 516 nm. A 15-fold molar excess of PPN is necessary for the full development of the color intensity. Beer's law is obeyed over the cerium concentration range 0.4–20 ppm and Sandell's sensitivity is found to be 0.016 μg/ cm². The effects of acidity, time, order of addition of reagents, temperature, reagent concentration, and diverse ions are reported. The proposed method offers the advantages of good sensitivity, simplicity, rapidity, selectivity, and a wider range of determination without the need for heating or extraction. Arsenic(III) and nitrite are also indirectly determined. The method is extended to the determination of cerium content in synthetic mixture corresponding to misch metal.     

Spectrophotometric determination of osmium (VIII) with promazine hydrochloride

Promazine hydrochloride is proposed as a new reagent for the spectrophotometric determination of osmium (VIII). The reagent forms orange oxidation product with osmium tetroxide at room temperature in acidic media. The effects of acid concentration, time, temperature, and foreign ions are reported. Beer's law is obeyed in the osmium concentration range 1–10 μg/ml.     

Aqueous complexation of thorium(IV), uranium(IV), neptunium(IV), plutonium(III/IV), and cerium(III/IV) with DTPA

Aqueous complexation of Th(IV), U(IV), Np(IV), Pu(III/IV), and Ce(III/IV) with DTPA was studied by potentiometry, absorption spectrophotometry, and cyclic voltammetry at 1 M ionic strength and 25 °C. The stability constants for the 1:1 complex of each trivalent and tetravalent metal were calculated. From the potentiometric data, we report stability constant values for Ce(III)DTPA, Ce(III)HDTPA, and Th(IV)DTPA of log β(101) = 20.01 ± 0.02, log β(111) = 22.0 ± 0.2, and log β(101) = 29.6 ± 1, respectively. From the absorption spectrophotometry data, we report stability constant values for U(IV)DTPA, Np(IV)DTPA, and Pu(IV)DTPA of log β(101) = 31.8 ± 0.1, 32.3 ± 0.1, and 33.67 ± 0.02, respectively. From the cyclic voltammetry data, we report stability constant values for Ce(IV) and Pu(III) of log β(101) = 34.04 ± 0.04 and 20.58 ± 0.04, respectively. The values obtained in this work are compared and discussed with respect to the ionic radius of each cationic metal.     

Spectrophotometric determination of titanium (IV) with chlorpromazine hydrochloride

Spectrophotometric Determination of Titanium(IV) with Chlorpromazine HydrochlorideThe extraction of titanium(IV)-thiocyanate complex from hydrochloric acid with chlorpromazine (CPA) dissolved in chloroform has been studied. The composition of the extracted species was found to be (CPAH⁺)₂[Ti(CNS)₆²⁻]. This complex, dissolved in chloroform, has maximum absorbance at 417 nm and a molar absorptivity of 2.6 × 10⁴ mol⁻¹ · cm⁻¹ · liter. Titanium(IV) was determined spectrophotometrically in the organic phase. Beer's law is obeyed in the titanium concentration range 0.2-2.2 μg/ml.     

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.     

Selective extraction-photometric redox determination of low concentrations of sulfur(IV), selenium(IV), tellurium(IV), and arsenic(III)

A procedure is proposed for the selective extraction-photometric determination of the acid-forming elements S(IV), Se(IV), Te(IV), and As(III) in their mixtures containing molecular forms or anions with different electron densities on donor atoms. The procedure is based on the difference in the oxidizability of analytes with the [SbCl₆]^? complex. The analytical ranges are found at different pHs of the medium, affecting the potential of the two-phase redox systems. The detection limits for sulfite, selenite, tellurite, and arsenite are 1 × 10^?3, 5 × 10^?5, 7 × 10^?5, and 1 μg/mL, respectively. The procedure is applied to the determination of selenium in H₂SO₄ of high-purity grade, which is used in the production of microelectronics items and in some agricultural samples. The error of analysis is no worse than 20%.     

Complex formation reactions of lanthanum(III), cerium(III), thorium(IV), dioxouranyl(IV) complexes with tricine

Equilibrium studies for the heavy metal ions La(III), Ce(III), Th(IV) and UO2(IV) (M) complexes of the zwitterionic buffer tricine (L) in aqueous solution are investigated. Stoichiometry and stability constants for the different complexes formed as well as hydrolysis products of the metal cations are determined at 25 degrees C and ionic strength 0.1 M NaNO3. The stability of the formed complexes are discussed in terms of the nature of the heavy metal cation. The solid complexes are synthesized and characterized by means of elemental analysis, FTIR, and TG analysis. The general molecular formulae of the obtained complexes is suggested to be [M(L)2](NO3)n-2(H2O)x, where n = the charge of the metal cation, x = no. of water molecules.     

Spectrophotometric determination of phosphate ions with the system cerium(III)Arsenazo III

A new method for the spectrophotometric determination of PO(3-)(4), based on the conversion of the complex of cerium(III) with arsenazo III (CeH(4)R(-)) into CePO(4) is proposed and used for the indirect spectrophotometric determination of phosphorus in ferro-silicon. The reaction between Ce(III) and arsenazo III has been studied spectrophotometrically and the stability constants of the complex CeH(4)R(-) have been determined: log beta(1) = 6.42 +/- 0.10 (for pH 1-3) and log beta(1) = 6.11 +/- 0.02 (for pH 5.5-7).     

Spectrophotometric determination of cerium(IV) using a phenothiazine derivative.

A simple, rapid and sensitive spectrophotometric method has been proposed for the determination of cerium(IV) using a phenothiazine derivative, propionyl promazine phosphate (PPP). This method is based on the formation of a red-colored radical cation upon a reaction of PPP with cerium(IV) in a phosphoric acid medium having maximum absorbance at 513 nm. Beer's law is valid over the concentration range of 1-11 microg/ml with a Sandell's sensitivity value of 16.14 ng/cm2. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys. Other phenothiazine derivatives viz. butaperazine dimaleate and propericiazine were also used for the determination of cerium(IV).     

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.     

Complexometric and spectrophotometric determination of thorium(IV), cerium(III), and uranium(VI), using quinizarin sulphonic acid after separation with ion-exchange resins

A method is described for the complexometric EDTA-titration and spectrophotometric determination of Th⁴⁺ Ce³⁺, and UO₂²⁺ in binary or ternary mixtures after primary separation with ion-exchange resin. As indicator or coloring agent, quinizarin sulphonic acid is used. The EDTA titration gives accurate results with Th⁴⁺ and Ce³⁺ only, but the spectrophotometric method proved to be suitable for determination of small quantities of the metal ions.     

Spectrophotometric determination of olanzapine by its oxidation with N-bromosuccinimide and cerium(IV)sulfate.

Three simple spectrophotometric methods have been described for the assay of olanzapine in its pure and pharmaceutical formulations. The direct method (A) is based on the drug oxidation with excess of N-bromosuccinimide in acidic medium and the two indirect methods (B and C) are based on the oxidation of the drug with excess of N-bromosuccinimide and cerium(IV)sulfate, followed by the reaction of the unconsumed oxidants with celestine blue. The calibration graphs were linear over the range 10 - 120 microg mL(-1) (method A), 0.5 - 6.0 microg mL(-1) (method B) and 0.6 - 3.0 microg mL(-1) (method C). After validation, the proposed methods were successfully applied to assay of olanzapine in its commercial tablets with mean percentage recoveries of 101.23 +/- 0.10, 96 +/- 0.10 and 94 +/- 0.04%. The mechanism of olanzapine oxidation with N-bromosuccinimide was also proposed.     

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.     

Spectrophotometric determination of H(2)-receptor antagonists via their oxidation with cerium(IV)

A simple, accurate and sensitive spectrophotometric method has been developed and validated for determination of H(2)-receptor antagonists: cimetidine, famotidine, nizatidine and ranitidine hydrochloride. The method was based on the oxidation of these drugs with cerium(IV) in presence of perchloric acid and subsequent measurement of the excess Ce(IV) by its reaction with p-dimethylaminobenzaldehyde to give a red colored product (lambda(max) at 464nm). The decrease in the absorption intensity of the colored product (DeltaA), due to the presence of the drug was correlated with its concentration in the sample solution. Different variables affecting the reaction were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9990-0.9994) were found between DeltaA values and the concentrations of the drugs in a concentration range of 1-20microgml(-1). The assay limits of detection and quantitation were 0.18-0.60 and 0.54-1.53microgml(-1), respectively. The method was validated, in terms of accuracy, precision, ruggedness and robustness; the results were satisfactory. The proposed method was successfully applied to the determination of the investigated drugs in pure and pharmaceutical dosage forms (recovery was 98.3-102.6+/-0.57-1.90%) without interference from the common excipients. The results obtained by the proposed method were comparable with those obtained by the official methods.     

Spectrophotometric determination of cerium with sulphanilic acid

In the presence of other rare earths, cerium(IV) can be determined spectrophotometrically by its reaction with sulphanilic acid with which it produces a red colour. Solutions containing 28-210 ppm of cerium absorb at 495 mmicro according to Beer's law. Other rare earths, except neodymium, and many common ions do not interfere. Strong oxidising agents and neodymium in greater than fifty times the concentration of cerium interfere with this method. The precision depends on the control of pH and time. Cerium alloys have been analysed by this method and the results are compared with those obtained by another spectrophotometric method.     

Spectrophotometric determination of nitrite

A new reagent for the absorptiometric determination of nitrite ion is used. Nitrite is reacted with 1-amino-4-naphthalenesulfonic acid to form a diazonium ion, which gives an orange color at pH 1.5 with maximum absorption at 310 nm, or an orange-red color at pH 4 with maximum absorption at 485 nm. Diazotation is fast at pH 1.5 but is stable only for 30 min after which the color fades continuously. However, at pH 4, the color develops after 1 hr and remains stable for >40 hr. The time of color development at pH 4 can be reduced to 30 min when heated to 60–70 °C for 5 min, but is followed by reduction of its intensity to half. The described method is found suitable for the determination of 0.1–5.0 ppm of the titled ion.     

Amperometric ascorbimetric determination of cerium(IV) and Iron(III) with two polarized electrodes

Summary Amperometric ascorbimetric determinations of cerium(IV) and ferric iron have been carried out at 50°C with two polarized electrodes at 200 and 100 mV respectively. The results obtained are fairly accurate and precise within ±1.0 per cent. A simple method for successive determination of cerium and iron has been developed; and conditions for such estimations have been established. At an acidity of 2.5 M with respect to sulphuric acid, it is possible to ward off the reduction of ferric iron and thereby cerium(IV) is successfully titrated with ascorbic acid in this medium. After completion of the reaction and then lowering the acid concentration to p_H 1.5 with aid of ammonium hydroxide, Fe^III is titrated with standard ascorbic acid yielding good results.