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Four sensitive, simple and specific methods were developed for the determination of desloratadine (DSL), a new antihistaminic drug in pharmaceutical preparations and biological fluids. Methods I and II are based on coupling DSL with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.6 where a yellow colored reaction product was obtained and measured spectrophotometrically at 485 nm (Method I). The same product could be measured spectrofluorometrically at 538 nm after excitation at 480 nm (Method II). Methods III and IV, on the other hand, involved derivatization of DSL with 2,4-dinitrofluorobenzene (DNFB) in borate buffer of pH 9.0 producing a yellow colored product that absorbs maximally at 375 nm (Method III). The same derivative was determined after separation adopting HPLC (Method IV). The separation was performed on a column packed with cyanopropyl bonded stationary phase equilibrated with a mobile phase composed of acetonitrile-water ( (Method IV). The four developed procedures were applied for the determination of DSL in tablets without any interference from the excipients. A low LOQ is a common requirement to support a clinical development program and when this is coupled with a simple procedure for sample preparation and feasible analytical tool, they would be the requirements of an optimized analytical method. Although the previously reported methods that were applied in pharmacokinetic studies of desloratadine possess the required low LOQ, they lack the simple sample preparation and method feasibility that were obtained in our spectrofluorometric method using NBD-Cl as a derivatizing agent where a low LOQ of 0.012 mg/ml was attained which allowed the analytical determination of DSL in spiked and real human plasma. ExperimentalMaterials and Reagents All chemicals were of analytical reagent grade. Desloratadine reference standard was kindly provided by ScheringPlough Corporation, U.S.A. Aerius tablets labeled to contain 5 mg DSL per tablet were purchased from commercial sources at a local pharmacy. Plasma samples were obtained from Mansoura University Hospital, Mansoura, Egypt, and were kept frozen until use after gentle thawing. Sep-Pak ® C18 solid phase extraction cartridges, 200 mg (SPE) were purchased from Waters Corporation (Milford, MA, U.S.A.). 4-Chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) was purchased from Sigma (St. Louis, MO, U.S.A.). A stock solution containing 2 mg/ml was freshly prepared in methanol. 2,4-Dinitrofluorobenzene (DNFB) was also purchased from Sigma (St. Louis, MO, U.S.A.). A stock solution containing 0.25% (v/v) was freshly prepared in methanol. Borate buffer solutions (0.2 M) were prepared by mixing appropriate volumes of 0.2 M boric acid and 0.2 M NaOH and adjusting the pH to 7.6 and 9.0 using a pH meter.29) Formic acid 85%, acetonitrile and methanol; AR Grade, Aldrich (St. Louis, MO, U.S.A.).Apparatus A Shimadzu UV-Visible 1601 PC spectrophotometer was used for the spectrophotometric measurements (P/N 206-67001). The recording range was 0-1.0.The f...

Evaluation of the use of microemulsions as eluents in high-performance liquid chromatographyAn overview of the use of microemulsions as eluents in HPLC is given. The separation mechanisms involved are discussed and the technique is compared to solvent modified micellar chromatography as well as to ordinary reversed-phase HPLC in order to evaluate differences and similarities. The microemulsion systems have been used for the separation of a number of antihypertensives and non steroidal antiinflammatory drug substances as well as for the analysis of bumetanide and acebutolol in plasma and urine. The plasma samples may be injected directly onto the HPLC system after a simple dilution.

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In this study, an eco‐friendly fast simple method was developed for simultaneous determination of norfloxacin and tinidazole based on thin‐layer chromatography and image‐processing analysis. The binary mixture was separated using reversed phase ‐ thin layer chromatography plates and 30% trifluoroacetic acid only as mobile phase. Mobile phase composition was optimized using Taguchi orthogonal array and Derringer's desirability function. The plates were viewed under UV lamp and photographed by iPhone camera followed by image processing with Fiji software using integrated density as the measured response. As decreasing illumination increases the sensitivity of the method, this method was applied on two different ranges for each drug. The first one was 0.6–6.0 and 0.9–9.0 µg/spot for norfloxacin and tinidazole, respectively measured on the original image with normal illumination. The second one was measured after decreasing the illumination of the captured images at 0.06–0.60 and 0.09–0.90 µg/spot for norfloxacin and tinidazole, respectively. The proposed method was successfully applied for the determination of both drugs in tablets dosage form without interference from the commonly encountered excipients. Analytical Eco‐Scale was used to evaluate the greenness profile of the proposed method and it was found to be excellent green analytical method.

A valid, sensitive and rapid spectrofluorimetric method has been developed and validated for determination of both tadalafil (TAD) and vardenafil (VAR) either in their pure form, in their tablet dosage forms or spiked in human plasma. This method is based on measurement of the native fluorescence of both drugs in acetonitrile at λem 330 and 470 nm after excitation at 280 and 275 nm for tadalafil and vardenafil, respectively. Linear relationships were obtained over the concentration range 4-40 and 10-250 ng/mL with a minimum detection of 1 and 3 ng/mL for tadalafil and vardenafil, respectively. Various experimental parameters affecting the fluorescence intensity were carefully studied and optimized. The developed method was applied successfully for the determination of tadalafil and vardenafil in bulk drugs and tablet dosage forms. Moreover, the high sensitivity of the proposed method permitted their determination in spiked human plasma. The developed method was validated in terms of specificity, linearity, lower limit of quantification (LOQ), lower limit of detection (LOD), precision and accuracy. The mean recoveries of the analytes in pharmaceutical preparations were in agreement with those obtained from the comparison methods, as revealed by statistical analysis of the obtained results using Student's t-test and the variance ratio F-test.