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Titrimetric and spectrophotometric assay of pantoprazole sodium sesquihydrate ( PSS) using cerium(IV) sulphate as the oxidimetric reagent is described. The methods are based on the oxidation of PSS with a measured excess of Ce(IV) sulphate followed by the determination of unreacted oxidant using different reaction schemes. In titrimetry, the unreacted oxidant was determined by back titration with ferrous ammonium sulphate ( FAS) in sulphuric acid medium. Spectrophotometry involves the reduction of unreacted Ce(IV) sulphate with a fixed quantity of Fe(II). The resulting Fe(III) is complexed with thiocyanate and the absorbance is measured at 470 nm. In both the methods, the amount of Ce(lV) sulphate reacted corresponds to PSS concentration. Titrimetry is applicable over 1-10 mg range whereas in spectrophotometry, the calibration graph is linear in the range of 0.5-7.0 μg/mL and the calculated molar absorptivity value is 1.58 × 10 L/mol cm. The validity of the proposed methods was tested by analyzing pure and dosage forms containing PSS. Statistical treatment of the results reflects that the proposed procedures are precise, accurate and easily applicable to the determination of PSS in pure form and in pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

Three simple, sensitive, accurate and indirect visible spectrophotometric methods have been developed for the estimation of lamotrigine (LMT) in both pure and in pharmaceutical preparations. They are based on the oxidation of lamotrigine with a known excess of cerium(IV) in acid medium. The unreacted cerium(IV) oxidize leuco crystal violet to crystal violet colored dye (Method A), leuco malachite green to bluish-green malachite green dye (Method B), leuco xylene cyanol FF to xylene cyanol FF bluish dye (Method C) and exhibiting absorption maxima (λmax) at 580, 610 and 610 nm, respectively. In these methods, the amount of cerium(IV) reacted corresponds to the amount of LMT. The results of the three methods have been validated statistically and by recovery studies. The results obtained in the proposed methods were in good agreement with the label claim. [ABSTRACT FROM AUTHOR]

A new, simple, highly sensitive spectrophotometric method for the determination of trace amounts of cerium(IV) is described. The method is based on the oxidation of leuco disulphine blue (LDSB) to its blue form of disulphine blue by Ce(IV) in a sulfuric acid medium (pH 1.3–3.0); the absorbance of the formed dye is measured in an acetate buffer medium (pH 3.0–4.8) at 635 nm. The color system obeys Beer's law in the concentration range from 0.5 to 5.5 μg mL–1 cerium with a molar absorptivity of 1.75 × 104 L mol–1 cm–1 and a Sandell's sensitivity of 0.008 μg cm–2. All variables were studied in order to optimize the reaction conditions. The developed method has been successfully applied to the determination of cerium in high purity rare-earth oxides, soil, natural water, plant tissue, human hair, and rock samples. [ABSTRACT FROM AUTHOR]