Stability-indicating spectrofluorimetric method with enhanced sensitivity for determination of vancomycin hydrochloride in pharmaceuticals and spiked human plasma: Application to degradation kinetics.

Based on investigating the relative fluorescence intensity of vancomycin hydrochloride (VCM) in methanol, a simple, highly sensitive, time-saving and specific spectrofluorimetric method was developed and validated. VCM fluorescence was measured at 335 nm when excited at 268 nm. Excellent linearity is obeyed in the concentration range 1-100 ng/mL with a detection limit of 5.94 pg/mL, a quantitation limit of 18.03 pg/mL and a very good correlation coefficient (r = 0.9999). Our method was applied to analyze VCM in pharmaceuticals as well as spiked human plasma. Moreover, VCM stability was studied when exposed to various degradation conditions such as oxidative, alkaline as well as acidic stress. Acidic and alkaline degradation kinetics of VCM was studied for the first time. The degradation follows pseudo-first-order kinetics. The apparent rate constants and half-life times were calculated. The Arrhenius equation was assessed and the activation energies of the degradation were also calculated. The developed method can be easily applied in quality control laboratories due to its sensitivity, specificity, simplicity and low cost.

Validated stability-indicating spectrofluorimetric methods for the determination of ebastine in pharmaceutical preparations.

Two sensitive, selective, economic, and validated spectrofluorimetric methods were developed for the determination of ebastine (EBS) in pharmaceutical preparations depending on reaction with its tertiary amino group. Method I involves condensation of the drug with mixed anhydrides (citric and acetic anhydrides) producing a product with intense fluorescence, which was measured at 496 nm after excitation at 388 nm.Method (IIA) describes quantitative fluorescence quenching of eosin upon addition of the studied drug where the decrease in the fluorescence intensity was directly proportional to the concentration of ebastine; the fluorescence quenching was measured at 553 nm after excitation at 457 nm. This method was extended to (Method IIB) to apply first and second derivative synchronous spectrofluorimetric method (FDSFS & SDSFS) for the simultaneous analysis of EBS in presence of its alkaline, acidic, and UV degradation products.The proposed methods were successfully applied for the determination of the studied compound in its dosage forms. The results obtained were in good agreement with those obtained by a comparison method. Both methods were utilized to investigate the kinetics of the degradation of the drug.

First and second derivative synchronous fluorescence and spectrophotometric spectroscopy for the simultaneous determination of fexofenadine hydrochloride in presence of its degradation products. Application to stability studies.

Two rapid, simple, sensitive, selective and economic derivative spectrophotometric (first [D1] and second [D2]) and synchronous spectrofluorimetric (FDSFS and SDSFS) methods have been developed for the analysis of fexofenadine hydrochloride (FXD) in the presence of its different degradation products. Derivative spectrophotometry (D1) was used to measure FXD at 223 nm in the presence of its alkaline or acidic degradation products, and at 211 nm in the presence of its oxidative degradation product. Derivative spectrophotometry (D2) was used to determine FXD at 217 nm in the presence of its alkaline or acidic degradation products, and at 215 nm in the presence of its oxidative degradation product; the UV degradation product was measured at 211 nm. Synchronous spectrofluorimetry (FDSFS) was used to measure FXD in the presence of its alkaline or acidic degradation products at 406 nm, and at 367 nm in the presence of its oxidative or UV degradation products. Synchronous spectrofluorimetry (SDSFS) was applied to determine the drug at 225 nm in the presence of its alkaline, acidic, oxidative or UV degradation products. The proposed methods were successfully applied for the determination of the studied compound in its commercial tablets. The results obtained were in good agreement with those obtained by the comparison method.

Spectrophotometric determination of acyclovir and ribavirin in their dosage forms.

Two simple, accurate, and reliable spectrophotometric methods have been developed for the determination of 2 antiviral drugs, acyclovir (ACV) and ribavirin (RBV), in their pharmaceutical formulations. These methods are based on oxidation of the 2 drugs with either cerium (IV) ammonium sulfate (Method A) or potassium persulfate (Method B). The products of oxidation in both methods are coupled with 3-methylbenzothiazolin 2-one hydrazone, producing a deep blue color with a maximum absorption wavelength at 630 nm. In Method A, the absorbance-concentration plots were linear over the ranges of 5-50 and 10-60 microg/mL with detection limits of 0.18 microg/mL (8 x 10(-7) M) and 0.63 microg/mL (2.58 x 10(-6) M) for ACV and RBV, respectively. In Method B, the ranges were 5-45 and 20-50 microg/mL with detection limits of 0.11 microg/mL (4.88 x 10(-7) M) and 1.40 microg/mL (5.73 x 10(-6) M) for the 2 drugs, respectively. The molar absorptivities were 4.1 x 10(3) and 3.65 x 10(3) L/mol/cm in Method A and 5.03 x 10(3) and 3.97 x 10(3) L/mol/cm in Method B for the 2 drugs, respectively. The proposed methods were applied successfully for the determination of the 2 drugs in their pharmaceutical formulations. The percentage recoveries +/- standard deviation were 99.57 +/- 0.86 and 100.82 +/- 0.46 for ACV; 99.41 +/- 1.08 and 100.35 +/- 1.03 for RBV. The results obtained were compared statistically with those given by official methods and showed no significant differences regarding accuracy and precision.