High-Performance Liquid Chromatographic Method for the Determination of Nimesulide in Pharmaceutical Preparations

A simple, rapid, and precise high-performance liquid chromatographic method for the determination of nimesulide in pharmaceutical preparations was proposed using Ibuprofen as an internal standard. The separation was performed on a CLC C₁₈ (5 m, 25 cm × 4.6 mm i.d.) column with a mobile phase consisting of an acetonitrile–0.05 M KH₂PO₄ buffer mixture of pH 7.00 (55 : 45, v/v). The detection was carried out at 230 nm and the linearity range was found to be 0.5–100 g/mL. The method has been applied successfully to the determination of nimesulide in pharmaceutical formulations. The recovery values were found to be in the range of 99.23–100.13% with RSD values of less than 0.97%.     

Diazocoupling reaction for the spectrophotometric determination of physiologically active catecholamines in bulk and pharmaceutical preparations

A simple and sensitive spectrophotometric method for the determination of four catecholamines viz., adrenaline bitartarate (ABT), methyldopa (MDP), dopamine hydrochloride (DPH), and levodopa (LDP), in both pure form and in pharmaceutical formulations is described. The method is based on the reaction of diazotized sulphanillic acid (DSA) with catecholamines in a basic medium to yield orange-red colored products having absorption maxima at 507 nm for MDP and at 475 nm for others analytes. The colored species obeyed Beer’s law in the range of 1–27, 0.5–17, 0.6–15, and 1.5–19.2 μg/mL for ABT, MDP, DPH, and LDP, respectively. The molar absorptivity values as obtained from Beer’s law data were found to be 0.812 × 10⁴, 0.947 × 10⁴, 0.927 × 10⁴, and 0.709 × 10⁴ L/(mol cm), while Sandell’s sensitivity values were observed to be 412.03, 25.15, 20.44, and 27.81 ng/cm² for ABT, MDP, DPH, and LDP, respectively. Common excipients did not interfere with the proposed method. The results of the proposed methods compare favorably with those of official methods. The proposed method offers a simplicity, reliability, rapidity, and accuracy compared to the existing methods. The text was submitted by the author in English.     

Interaction of an antidepressant buzepide methiodide with DNA immobilized on the glassy carbon electrode

In the present study, a DNA-biosensor was prepared using immobilization technique to investigate the interaction between an antidepressant, buzepide methiodide (BZP) and calf thymus DNA. BZP showed a quasireversible peak in Britton-Robinson (BR) buffer of pH 5 at bare glassy carbon electrode (GCE). At DNA modified GCE, the peak potential of BZP was observed to be shifted towards positive potential revealing intercalative mode of binding. The binding constant and stoichiometry between DNA and BZP are calculated to be 1.908×10(5)M(-1) and 0.982, respectively. The spectroscopic techniques viz., spectrofluorescence and UV-vis absorption have also been employed to understand the interaction between BZP and DNA. The results serve as a reference for the interaction of BZP with DNA base pairs in the natural environment of living cells.     

Bulk Modification of Carbon Paste Electrode with Bi2O3 Nanoparticles and Its Application as an Electrochemical Sensor for Selective Sensing of AntiHIV Drug Nevirapine

Bi₂O₃ nanoparticles were synthesized by solution combustion method and utilized for fabrication of an electrochemical sensor [carbon paste electrode modified with Bi₂O₃ (CPE‐Bi₂O₃)] for nevirapine (NVP). Electrode materials were characterized by XRD, FTIR, TG‐DTA, AFM and SEM‐EDS methods. CPE‐Bi₂O₃ was electroreduced (Er) in KOH in the potential range of ?1.3–0 V to obtain CPE‐ErBi₂O₃. CPE‐ErBi₂O₃ exhibited electrocatalytic activity towards the oxidation of NVP. Under optimized conditions, linearity between the peak current and NVP concentration was observed in the range of 0.05–50 µM. Further, the sensor was used for the assay of NVP in tablets and biological samples.     

Development and validation of a stability-indicating LC method for the assay of adapalene in bulk drug and pharmaceutical formulations

A simple and sensitive reverse phase HPLC method for the determination of adapalene (ADP) in bulk drug samples and pharmaceutical formulations has been developed and validated. The separation of ADP was achieved on an Inertsil ODS-3V (5 ??m, 15 cm ± 4.6 mm i.d.) column using UV detector at 230 nm. The mobile phase consisted of ammonium acetate (25 mM, pH 3.0), methanol and tetrahydrofuran (18: 42: 40 v/v). The linear range of detection was 2?C200 ??g/mL (R = 0.9991). Intra- and inter-day assay relative standard deviation values were less than 0.5%. The method has been successfully applied to the determination of ADP in pharmaceutical preparations. The excipients commonly present in formulations did not interfere with the assay of ADP. Analytical parameters were calculated and complete statistical evaluation was performed.     

Binding Mechanism of Bioactive Cetirizine Hydrochloride to Sudlow’s Site I of Serum Albumins

The mechanism of interaction of an anti-allergic drug, cetirizine dihydrochloride, with the proteins bovine and human serum albumins has been investigated by spectrofluorimetry, FTIR, UV-vis absorption and circular dichroism methods at physiological conditions. The drug was found to quench the fluorescence intensity of the protein through a dynamic quenching mechanism. Various binding parameters were evaluated based on fluorescence quenching studies carried out at 293 K, 301 K and 308 K. The nature of the binding force operating between the drug and protein was proposed, based on the measured thermodynamic parameters. A change in the secondary structure of the protein was evident from the circular dichroism measurements, wherein the α-helicity decreased from 65.69% to 51.23% and from 42.7% to 38.55% for the CTZ–BSA and CTZ–HSA systems, respectively. Based on Förster’s theory of non-radiative energy transfer, the distance between the protein and drug was determined. The common blood plasma ions K⁺, Cu²⁺, Ni²⁺, Mn²⁺ and Co²⁺ were found to influence the binding of the drug to the protein. Displacement experiments were carried out to determine the binding site for drug on the protein. These studies, coupled with other spectroscopic results, revealed that the drug was bound to the hydrophobic pocket located in sub domain IIA of site I.     

Fabrication of an Electrochemical Sensor Based on Multiwalled Carbon Nanotubes for Almotriptan

In the present work, the electrochemical behavior of an antimigraine drug, almotriptan malate (ALM), on a multiwalled carbon nanotube (MWCNT) film modified glassy carbon electrode under cyclic voltammetry was described for the first time. A significant enhancement in the oxidation peak current of ALM was noticed at MWCNT‐GCE. This property was exploited to develop a simple, sensitive and time‐saving differential pulse voltammetric method for the determination of ALM in bulk and pharmaceutical samples. A linear relationship was observed between concentration and peak current with a correlation coefficient of 0.9915 in the range of 0.25–37.5 µM ALM.     

Spectrophotometric determination of certain vicinal dihydroxybenzene derivatives in pharmaceutical preparations.

A simple, rapid and sensitive spectrophotometric method for the assay of certain adrenergic drugs, [pyrocatechol (PC), levodopa (LD), methyldopa (MD) and dopamine (DP)] is described. The method involves the oxidation of o-dihydroxybenzene derivatives by K2CrO4 followed by oxidative coupling with sulfanilic acid (SPA), leading to the formation of a red or violet colored product having maximum absorbance at 490-495 nm for LD, MD and DP or at 560 nm for PC. This method has been successfully applied to the determination of LD, MD and DP in tablets and injections of pharmaceutical preparation. The common excipients do not interfere with the proposed method. A statistical comparison of these results with those of a reported method shows good agreement and indicates no significant difference in precision.     

Spectrophotometric Determination of Antiallergic Drug in Bulk Powder and in Its Pharmaceutical Formulations

Two simple, rapid and selective spectrophotometric methods have been described for the determination of promethazine hydrochloride (PMH) either in pure or pharmaceutical formulations. The methods are based on the formation of a green colored product with sulphanilic acid (SPA) in presence of N-bromosuccinimide (NBS) or a red colored, chloroform soluble product with p-nitroaniline (PNA) in presence of ceric ammonium sulphate (CAS). The chromogen formed has maximum absorption at 600 nm and at 510 nm with SPA and PNA, respectively. The optimum reaction conditions and other analytical parameters are evaluated. Beer's law is valid in the concentration range of 0.5–25 g/mL (R= 0.9983) with SPA and 2–75 g/mL (R = 0.9981) with PNA. Molar absorptivity values as calculated from the Beer's law data are 5.54 × 10³ L/mol/cm and 3.05 × 10³ L/mol/cm for SPA and PNA, respectively. The results are in good agreement with those of the official method. No interference was observed from common pharmaceutical excipients.