Abstract
A selective and new spectrophotometric method is described for determination of five 1,4 dihydropyridine drugs (1,4- DHP); namely nifedipine (NIF), nicardipine (NIC), nimodipine (NIM), felodipine (FEL) and amlodipine (AML). The method is based on a coupling reaction between the cited drugs and vanillin reagent in acidic condition. Under optimized conditions, the red coloured products were measured at 500 nm for NIF, NIC, NIM and FEL or at 479 nm for AML. Molar absorptivities were ranged from 0.575 × 104 － 1.065 × 104 l·mol-1·cm-1, Beer’s law was obeyed at 5 - 70 μg/mL concentration range and the limit of detection was ranged from 0.150 - 1.500 μg/mL. The proposed method was successfully extended to pharmaceutical preparations tablets and capsules and comparison by Student’s t-test and variance ratio F-test showed no significant difference.
Highlights
1,4-DHP drugs, as shown in Figure 1, are primarily used for treatment of cardiovascular diseases such as hypertension, angina and some forms of cardiac arrhythmias
An aliquot of 1.0 mL of the standard drugs solution was transferred into a 10-mL calibrated flask. 1.0 mL of vanillin reagent was added, mixed well, the reaction was allowed to proceed for 30 min at 50 ̊C, for NIF, NIC, NIM and FEL or 35 min at 70 ̊C, for AML the resulting coloured products were measured at 500 nm for NIF, NIC, NIM, FEL or 479 nm for AML; against blanks which treated
Adding vanillin reagent to 1,4-DHP drugs in the presence of hydrochloric acid and at a high temperature, showed a red colour which can be measured spectrophotometrically (Figure 3), this is a novel reaction for detremination of these drugs and it was suggested as a coupling reaction between the aldehydic group of vanillin and active methyl group which present in all the cited drugs, the suggested mechanism involved one reaction step and did not depend on the presence of the -NO3 group as in some cited drugs structure (NIF, NIC and NIM)
Summary
1,4-DHP drugs, as shown in Figure 1, are primarily used for treatment of cardiovascular diseases such as hypertension, angina and some forms of cardiac arrhythmias. 1,4-DHP drugs, as shown, are primarily used for treatment of cardiovascular diseases such as hypertension, angina and some forms of cardiac arrhythmias. These agents are useful in other pathological states, such as seizures and central ischemic disorders through their action on slow L-type channels [1,2] they have the advantages of little interaction with other cardiovascular drugs, such as digoxin or warfarin that are often used concomitantly with them [3]. The therapeutic importance and successful clinical uses of these drugs have promoted the development of many analytical methods for their determination in bulk, in their pharmaceutical formulations and in biological fluids. 2.2.2. 1,4-DHP Drugs Stock Solution Reference standards of purecited drugs (NIF, atenolol, NIC HCl, NIM, FEL, AML besylate and Metoprolol) were generously supplied by their respective munufacturers
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