Titrimetric and Spectrophotometric Assay of Pantoprazole in Pharmaceuticals Using Permanganate

Titrimetric and spectrophotometric assay of pantoprazole sodium (PPS) using permanganate as the oxidimetric reagent is described. In titrimetry, PPS is treated with a measured excess of permanganate in H2SO4 medium followed by the determination of unreacted oxidant by back titrating with a standard iron(II) solution. Spectrophotometry involves addition of a known excess of permanganate to PPS in H2SO4 medium followed by the measurement of absorbance of the residual permanganate at 545 nm. In both the methods, the amount of permanganate reacted corresponds to the PPS content. Experimental conditions that provide wide linear range, maximum sensitivity and selectivity, and accuracy and precisions have been optimized. In titrimetry, the calculations are based on a 1:1 (PPS : KMnO4) reaction stoichiometry and the method is applicable over 1.0-7.0 mg range. In spectrophotometry, Beer’s law is obeyed over the concentration range 15.0-150.0 µg mL-1. The linear regression equation of the calibration graph is A = 0.78 + 0.005 C with a regression coefficient (r) of 0.9982 (n = 11). The apparent molar absorptivity is calculated to be 2.213 × 103 l mol-1cm-1 and the Sandell sensitivity is 0.1954 µg cm-2. The limits of detection (LOD) and quantification (LOQ) calculated as per the ICH guidelines are 0.73 and 2.21 µg mL-1, respectively. Accuracy and precision of the assays were determined by computing the intra-day and inter-day variations at three different levels of PPS; the intra-day and inter-day RSD was < 3.09 % and the accuracy was better than 3.5 %. The methods were successfully applied to the determination of PPS in three different brands of tablets with good accuracy and precision, and without detectable interference by excipients. The accuracy was further ascertained by placebo blank and synthetic mixture analyses and also by recovery experiments via standard-addition procedure.

Sensitive and Selective Extractive Spectrophotometric Method for the Determination of Hydroxyzine Dihydrochloride in Pharmaceuticals

Hydroxyzine dihydrochloride (HDH), a piperazine H1-receptor antagonist and antihistamine, is a rapid acting anxiolytic used principally as an anti-emetic. A sensitive, selective, and precise and accurate spectrophotometric method based on the formation of an ion-pair with orange II (ORG II) as ion-pair complexing agent was developed and validated for the determination of HDH in pharmaceuticals. The chloroform-extractable ion-pair complex exhibited an absorption maximum at 480 nm. Optimization of different experimental conditions is described. Beer’s law is obeyed in the range of 1.5-15 μg mL-1 with an apparent molar absorptivity value of 2.07 x 104 L mol-1 cm-1 and Sandell’s sensitivity value of 0.0216 μg cm-2. The limit of detection (LOD) and limit of quantification (LOQ) are 0.14 and 0.41 μg mL-1, respectively. A Job’s plot of absorbance versus molar ratio of HDH to ORG II indicated (1:2) stoichiometric ratio. Within- and between-day relative standard deviations at three different concentration levels were < 3%. The developed method was successfully applied to commercial tablets. The results obtained were in good agreement with those obtained using the official method. No interference was encountered from co-formulated substances. Recoveries were 96-109 %.

Titrimetric and Spectrophotometric Methods for the Assay of Ketotifen Using Cerium(IV) and Two Reagents

One titrimetric and two spectrophotometric methods are described for the determination of ketotifen fumarate (KTF) in bulk drug and in tablets using cerium(IV) as the oxidimetric agent. In titrimetry (method A), the drug was treated with a measured excess of cerium(IV) in H2SO4 medium and after a standing time of 10 min, the surplus oxidant was determined by back titration with iron(II). The spectrophotometric procedures involve addition of a known excess of cerium(IV) to KTF in acid medium followed by the determination of unreacted oxidant by reacting with either p-dimethyl amino benzaldehyde and measuring the resulting colour at 460 nm (method B) or o-dianisidine and subsequent measurement of the absorbance of coloured product at 470 nm (method C). Titrimetric assay is based on a 1 : 2 reaction stoichiometry between KTF and cerium(IV) and the method is applicable over 2-18 mg range. In spectrophotometry, regression analysis of Beer's law plots showed a good correlation in 0.4-8.0 and 0.4-10.0 g mL(-1) KTF ranges for method B and method C, respectively, and the corresponding molar absorptivity coefficients are calculated to be 4.0 × 10(4) and 3.7 × 10(4) L mol(-1) cm(-1).

Volumetric and spectrophotometric determination of oxcarbazepine in tablets

Two cerimetric procedures are described for the assay of oxcarbazepine (OXC) in bulk drug and in tablets. Titrimetry (method A) is based on the reaction of OXC by a measured excess cerium(IV) sulphate in sulphuric acid medium and the determination of the unreacted oxidant by titration with iron(II) solution using ferroin as indicator. Spectrophotometry (method B) is based on oxidation of OXC by cerium(IV) in perchloric acid (HClO4) medium and the determination of the unreacted oxidant using a colour reaction with p-dimethylaminobenzaldehyde (p-DMAB) having an absorption maximum of 460 nm. The titrimetric method is applicable in the range of 2.0-20.0 mg OXC with a 1:2 reaction stoichiometry [OXC:Ce(IV)]. In the spectrophotometric method a rectilinear relationship is obtained over the concentration range of 0.3-6.0 µg mL-1 OXC. The linear regression equation of the calibration graph is A = 0.9820-0.1477 C with a regression coefficient (r) of -0.9967 (n = 6). The molar absorptivity is calculated to be 3.76 × 104 L mol-1 cm-1 and the Sandell sensitivity is 0.0067 µg cm-2. The limits of detection (LOD) and quantification (LOQ) values are calculated according to ICH guidelines. The methods are successfully applied to the determination of OXC in tablets.

Rapid titrimetric and spectrophotometric determination of ofloxacin in pharmaceuticals using N-bromosuccinimide

One titrimetric and two spectrophotometric methods have been described for the determination of ofloxacin (OFX) in bulk drug and in tablets, employing N-Bromosuccinimide as an analytical reagent. The proposed methods involve the addition of a known excess of NBS to OFX in acid medium, followed by determination of unreacted NBS. In titrimetry, the unreacted NBS is determined iodometrically, and in spectrophotometry, unreacted NBS is determined by reacting with a fixed amount of either indigo carmine (Method A) or metanil yellow (Method B). In all the methods, the amount of NBS reacted corresponds to the amount of OFX. Titrimetry allows the determination of 1-8 mg of OFX and the calculations are based on a 1:5 (OFX:NBS) reaction stoichiometry. In spectrophotometry, Beer's law is obeyed in the concentration ranges 0.5-5.0 µg/mL for method A and 0.3-3.0 µg/mL for method B. The molar absorptivities are calculated to be 5.53x10(4) and 9.24x10(4) L/mol/cm for method A and method B, respectively. The methods developed were applied to the assay of OFX in tablets, and results compared statistically with those of a reference method. The accuracy and reliability of the methods were further ascertained by performing recovery tests via the standard-addition method.

Sensitive spectrophotometric assay of simvastatin in pharmaceuticals using permanganate

Two simple, sensitive, selective and inexpensive spectrophotometric methods are described for the determination of simvastatin (SMT) in bulk drug and in tablets using permanganate as the oxidimetric reagent. In method A, SMT is treated with a measured excess of permanganate in acetic acid medium and the unreacted oxidant is measured at 550 nm, whereas in method B the reaction is carried out in alkaline medium and the resulting manganate is measured at 610 nm. In method A, the amount of permanganate reacted corresponds to the SMT content and the absorbance is found to decrease linearly with the concentration; and in method B, the absorbance increases with concentration. The working conditions of assays were optimized, and the methods were validated according to the current ICH guidelines. Under optimum conditions, SMT could be assayed in the concentration ranges, 1.47 - 17.67x10-5 and 2.27 - 27.18 x10-6 mol/L by method A and method B, respectively. The calculated molar absorptivities are 3.2 x 10³ and 2.5 x 10(4) L/mol/cm for method A and method B, respectively with corresponding Sandell sensitivity values of 0.0387 and 0.0178 μg/cm². The limits of detection (LOD) and quantification (LOQ) have also been reported. Accuracy and precision for the assay were determined by calculating the intra-day and inter-day at three concentrations; the intra-day RSD was < 2% and the accuracy was better than 2.15 % (RE). The methods were applied successfully for the determination of SMT in tablet dosage form with a high percentage of recovery, good accuracy and precision, and without measurable interference by the excipients. The accuracy was further ascertained from placebo and synthetic mixture analysis and also from the spike-recovery method.