Micellar-Enhanced Spectrofluorimetric Method for Quantification of Diclofenac Potassium in Pure Form, in Pharmaceutical Preparations and Human Plasma

A rapid, simple and economical spectrofluorimetric method for the determination of diclofenac potassium in pure form, in pharmaceutical preparations and in human plasma has been developed. The method is based on the enhancement of the fluorescence signal of diclofenac potassium by the addition of sodium dodecyl sulphate in McIvaine buffer with a pH of 5. Different experimental conditions such as buffer type, pH, type and concentration of surfactants were investigated. The fluorescence intensity of the solution was recorded at 361 nm after excitation at 243 nm. The method shows linearity in the concentration range of 0.2 μg mL–1–10 μg mL–1 with a good correlation coefficient of 0.997. The relative standard deviation value was 3.62 (n = 7). The limit of detection and limit of quantification were calculated to be 2.84 × 10–3 μg mL–1 and 9.47 × 10–3 μg mL-1, respectively. The effect of excipients and co-administrated drugs was investigated and no interference was observed. The method was successfully applied for the determination of diclofenac potassium in pure form, in pharmaceutical products and in human plasma. The percentage recoveries obtained ranged from 100.25% to 102.16% for pure form and 97.50% to 102.00% for pharmaceutical products and from 98.50% to 101.67% for human plasma.

Using a 3-hydroxyflavone derivative as a fluorescent probe for the indirect determination of aminothiols separated by ion-pair HPLC

Homocysteine, cysteine, cysteinyl-glycine, and glutathione are significant biological aminothiols (ATs) that are marker-molecules in Down syndrome, Alzheimer's disease, or have been implicated as risk factors in atherosclerosis and other vascular diseases, and therefore rapid determination of these molecules is desirable. After reduction of the disulfides, a widely used method utilizes derivatization with ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD-F) as a fluorogenic probe prior to reversed-phase HPLC separation followed by fluorescence detection. The traditional HPLC determination of ATs is time consuming and economically expensive. We have developed an ion-pair HPLC method coupled with indirect fluorescence detection after post-column reaction with a 2,4-dinitrobenzenesulfonate derivative of a 3-hydroxyflavone. The accuracy, precision, post-column temperature and residence time, and limit-of-detection were evaluated. Sample throughput and reduced sample preparation time of over an hour for the existing methods to less than 20 minutes for the new method is also demonstrated. No statistical differences in HCy, Cys, or Cys-Gly determinations in plasma samples were observed between our method and the traditional HPLC method.