HPTLC method for direct determination of gemifloxacin mesylate in human plasma.

Novel, simple and sensitive high performance thin-layer chromatography (HPTLC) with fluorescence detection has been successfully developed and validated for determination of gemifloxacin mesylate (GFX) in plasma samples without prior pretreatment. Montelukast (MK) was used as internal standard. GFX and MK in plasma samples were separated using a mobile phase consisting of a mixture of ethyl acetate:methanol:25% ammonia, (8:4.5:3, v/v/v). The emission intensity was measured using optical filter K400 after excitation at 342 nm. The Rf values for GFX and MK were 0.45±0.03 and 0.79±0.02, respectively. Under the optimum conditions, a linear relationship with good correlation coefficient (r=0.9965, n=6) was obtained in concentration range of 3-180 ng/band. The LOD and LOQ of the proposed method were 0.45 and 1.5 ng/band, respectively. The accuracy of the method was proved as the recovery % of GFX from spiked human plasma was 94.21-101.85%. The efficiency of the proposed method was confirmed by in-vivo application on human plasma in real patient samples. Moreover, the stability of GFX in plasma was carefully tested at different conditions and compared to others in aqueous solution.

Analysis of some antifungal drugs by spectrophotometric and spectrofluorimetric methods in different pharmaceutical dosage forms.

Simple spectrophotometric and spectrofluorimetric methods are suggested for the determination of antifungal drugs; clotrimazole, econazole nitrate, ketoconazole, miconazole and tolnaftate. Spectrophotometric one depends on the interaction between imidazole antifungal drugs as n-electron donor with the pi acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in methanol or with p-chloranilic acid (p-CA) in acetonitrile. The produced chromogens obey Beer's law at lambda(max) 460, and 520 nm in the concentration range 22.5-200 and 7.9-280 microg ml(-1) for DDQ, and p-CA, respectively. Spectrofluorimetric method is based on the measurement of the native fluorescence of ketoconazole at 375 nm with excitation at 288 nm and or the induced fluorescence after alkaline hydrolysis of tolnaftate with 5 M NaOH solution at 420 nm with excitation at 344 nm. Fluorescence intensity versus concentration is linear for ketoconazole at 49.7-800 ng ml(-1) while for tolnaftate, it is in the range of 20.4-400 ng ml(-1). The proposed methods were applied successfully for the determination of all the studied drugs in their pharmaceutical formulations.

Colorimetric determination of theophylline and aminophylline with diazotized p-nitroaniline.

The reactions of theophylline and aminophylline with diazotized p-nitroaniline in alkaline medium have been studied and developed into a sensitive assay for both drugs. The yellow azo-dyes formed with theophylline and aminophylline show maximum absorption at 440 and 410 nm respectively. Beer's law is valid within the concentration range 2-16 mug/ml for theophylline and 1-8 mug/ml for aminophylline. All variables which affect the reactions were studied and optimized. The proposed method has been successfully applied to determination of the drugs in their commercially available dosage forms. Statistical analysis of the results revealed that the proposed method is as precise and accurate as the official USP procedure.

Spectrofluorometric assay of thiamine hydrochloride in injections and multivitamin preparations.

A spectrofluorometric method is described for the determination of thiamine hydrochloride. The method is based on formation of a fluorescent product by oxidation of thiamine HCl with 2,3,5,6-tetrabromo-1,4-benzoquinone in aqueous acetonitrile solution. The reaction product is stable for at least 6 h and shows excitation and emission maxima around 355 and 420 nm, respectively. The method is highly selective for thiamine HCl in the presence of other B vitamins. Thiamine HCl can be determined at concentrations as low as 20-160 ng/mL of the final solutions. When the method was applied to the determination of thiamine HCl added to some commercially available multivitamin preparations, recoveries were 98.78-99.98%.

Simple and rapid spectrophotometric method for determination of adrenaline and isoprenaline.

A simple, rapid, and specific method for determination of adrenaline bitartrate and isoprenaline sulfate was developed. The method is based on the oxidation reaction in aqueous solution of either adrenaline bitartrate or isoprenaline sulfate in the presence of silver oxide to give a red aminochrome measurable at 490 nm. The color is stable for 2 h. Beer's law is valid within a concentration range of 5-80 micrograms/mL for each drug. All variables were studied to optimize the reaction conditions. The method is specific for catecholamine drugs having a secondary amine in the side chain. Other catecholamines such as orciprenaline and noradrenaline do not interfere, and no interference was observed in the presence of common pharmaceutical adjuvants. Interference due to sodium metabisulfite and sodium chloride was circumvented. The validity of the method was tested by analyzing adrenaline injections and isoprenaline tablets. Good recoveries were obtained for these preparations. The results were comparable to those obtained by official procedures. The proposed method is also recommended as a stability indicating assay for oxidative degradation of both drugs.

Short communication.

A simple and rapid calorimetric method for the determination of 10 sulphonamides as single entities and sulphamethoxazole in combination with trimethoprim without prior separation was developed. The method is based on the reaction of sulphonamide with phenothiazine and N-bromosuccinimide at pH 6 to produce a blue coloured product after acidification. The chromogen for all the sulphonamides was measured at 605 nm. The effect of several variables on colour development (concentration of phenothiazine and N-bromosuccinimide, time, pH) were established. Beer's Law was obeyed for all the drugs. The method was successfully applied to the analysis of single component sulphonamide tablets and ophthalmic solutions, with average results of labelled claim of 96.7 +/- 0.95 to 100.67 +/- 1.2. A good correlation was observed between molar absorptivities and pK(a) values of the sulphonamides (r = 0.9005).

A rapid spectrophotometric method for determination of piperazine.

A spectrophotometric method has been developed for the determination of piperazine and its salts (citrate, phosphate, and tartrate) without prior separation, based on the interaction of piperazine or any of its salts with phenothiazine and N-bromosuccinimide in aqueous methanol. The products exhibit absorption maxima at 448, 595 and 645 nm. Measurements are made at 595 nm. Beer's law is obeyed in the concentration range 0.5-5 mug/ml for piperazine salts and 0.5-3 mug/ml for piperazine hexahydrate. The method is rapid, simple and successful for analysis of some pharmaceutical preparations.

Colorimetric determination of C-2 unsubstituted phenothiazines, using morpholine and N-bromosuccinimide.

A colorimetric method for quantitative determination of 6 C-2 unsubstituted phenothiazine derivatives is described. The method is based on reaction of phenothiazine derivative with morpholine and N-bromosuccinimide reagents in aqueous methanol at 60 degrees C to produce a blue color. Beer's law is obeyed in a wide range of concentrations for all 6 compounds at 660 nm. Optimum analytical conditions were determined and the produced color is stable for at least 24 h. Analytical data for determination of the pure compounds are presented together with the application of the proposed method to analysis of some pharmaceutical preparations. The results compare favorably with those of official methods. Furthermore, the method is specific for intact drug in the presence of oxidative decomposition products. The reaction product has been isolated and identified and a possible reaction mechanism is suggested.

Spectrophotometric determination of nitrazepam in tablets.

A sensitive spectrophotometric method is reported for the determination of nitrazepam either in pure form or in tablets. The method is based on reduction with zinc dust and calcium chloride followed by reaction with sodium pentacyanoaminoferrate(II) to give a violet product having an absorbance maximum at 560 nm. Beer's law is obeyed over the concentration range 1-20 mug ml in the final solution. The common excipients in tablets do not interfere. The recovery and precision are similar to those of the official B.P. method.

Colorimetric determination of certain phenothiazine drugs by using morpholine and iodine-potassium iodide reagents.

A colorimetric method was developed for the quantitative estimation of 11 phenothiazine drugs. The method is based on the interaction of unsulfoxidized drug with morpholine and iodine-potassium iodide reagents. The interaction for all studied phenothiazine drugs yields a blue product with 2 absorption maxima: one in the range of 620-640 nm with lower molar absorptivity and the other in the range of 662-690 nm with higher molar absorptivity. The color was stable for at least 10 h. The reproducibility and recovery of the method were excellent. The method was applied successfully to the analysis of various commercially available phenothiazines in different dosage forms. The results were comparable to those obtained by official procedures. The suitability of the method for detection and estimation of promethazine excreted in urine has been suggested by preliminary experiments. Reaction products have been isolated and identified.

Determination of certain phenothiazine drugs with diazotized p-nitroaniline.

A colorimetric method for the determination of 7 phenothiazine drugs by interaction with diazotized p-nitroaniline has been developed. Neither the degradation products of the drugs nor the common excipients in pharmaceutical preparations interfere.

Spectrophotometric determination of ephedrine hydrochloride and phenylephrine hydrochloride.

A method is described for quantitative determination of the sympathomimetic amines ephedrine HCl and phenylephrine HCl. The method is based on the interaction of N-alkylvinylamine formed from the condensation of the free secondary amine group and acetaldehyde with chloranil to give a vinylamino-substituted quinone. The colored product for ephedrine HCl and phenylephrine HCl exhibits 2 maxima at about 320 and 680 nm. All variables were studied to optimize reaction conditions. The relationship between absorbance and concentration was linear within 1-25 micrograms/mL under the conditions studied for both drugs at both wavelengths. The method has been applied to the analysis of some pharmaceutical formulations including tablets and eye drops with good recoveries (98.75-100.4%).

Polarographic estimation of antazoline hydrochloride.

The dc-polarographic investigation of antazoline hydrochloride in aqueous acidic media is described. Using potassium chloride-hydrochloric acid mixture as the supporting electrolyte (pH = 3.25), antazoline hydrochloride was electrochemically reduced at the dropping mercury electrode, with the production of two waves with E1/2 values of --1.35 and --1.65 V respectively. As revealed from the study of the effect of mercury column height, pH of the medium and concentration of the depolarizer, the polarographic reduction of the antazolinium cation is preceded by a catalytic H-wave. The diffusion-controlled nature of the electrode process permitted the quantitative determination of antazoline hydrochloride in concentrations down to 1.0 . 10(-4)M. Application of the presented procedure to the analysis of different dosage forms of the compound studied proved successful and compared favourably with official estimations of anatazoline salts. In view of its simplicity, accuracy and sensitivity, the presented polarographic method can be recommended for routine analysis of antazoline formulations.