A transition metal complex, oxovanadium(IV) salen (where salen represents N,N -bis(salicylidene)ethylenediamine) is immobilized on glassy carbon (GC) electrodes and utilized for electrocatalytic oxidation of cysteine. In presence of oxovanadium(IV) salen, increased oxidation current is observed due to the effective oxidation of cysteine by the electrogenerated oxovanadium(V) salen species. The oxidation current linearly varies with the concentration of cysteine from 0.1 to 1.0 mM. The modified electrode has good sensitivity and low limit of detection. These properties make the oxovanadium(IV) salen as an effective electrocatalyst for the determination of cysteine.

Aim:Some literatures revealed that the high performance liquid chromatography (HPLC) method for single component or multicomponent analysis of montelukast sodium with other drugs. However, these methods deals with time consuming, so it is necessary to develop a cost-effective and less time consuming method for the estimation of doxofylline and montelukast sodium in combined pharmaceutical formulation.Materials and Methods:The separation was performed on an inertsil C8 (5 μm, 4.6 × 250 mm) column in isocratic mode with the mobile phase consisting a mixture of methanol and sodium phosphate buffer (75:25 v/v, pH 6.5 adjusted with orthophosphoric acid). The mobile phase was pumped at a flow rate of 1 mL min-1 and eluents were monitored at 230 nm.Results:The selected chromatographic conditions were found to separate doxofylline (retention time = 3.4 min) and montelukast sodium (retention time = 5.5 min) with a resolution of 5.47. The proposed HPLC method was validated with respect to linearity, accuracy, repeatability, specificity, robustness, and ruggedness as per International Conference on Harmonisation guidelines Q2(R1), November 2005 (Validation of Analytical Procedures: Text and Methodology). The percentage recoveries for doxofylline and montelukast sodium ranged from 98.1% to 101.7% and 98.2 to 101.9%, respectively, which indicated that the above method was enough accurate and precise.Conclusions:Hence, it was concluded that the developed method is suitable for routine analysis of these combination due to its less analysis time.

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