Quantitative determination of some thiazole cephalosporins through complexation with palladium (II) chloride

A simple and sensitive spectrophotometric method has been developed for the determination of five cephalosporins namely cefpodoxime (CFPD), ceftizoxime (CTIZ), ceftazidime (CZD), ceftriaxone (CTRX), and cefixime (CXIM). This method is based on the formation of yellow to yellowish brown complex between palladium (II) chloride and the investigated cephalosporins in the presence of sodium lauryl sulphate (SLS) as surfactant. The reaction conditions were studied and optimized. The procedure was validated. For each drug, the composition of this complex as well as its stability constant were also investigated. The proposed method was used for the determination of the above-mentioned drugs in their commercial preparations. The results were compared statistically with either official or published methods and showed no significant difference between the two methods.     

Atrophy of the stria vascularis, a common cause for hearing loss

Atrophy of the stria vascularis is a genetically determined deafness of aging characterized by a bilateral symmetrical sensori-neural hearing loss showing flat audiometric patterns and excellent speech discrimination. The temporal bones of individuals exhibiting this type of hearing loss were studied by serial sections and surface preparations for light microscopy and by electron microscopy. The atrophic changes are most severe in the apical regions of the cochleas and involve the marginal, intermediate and basal cells in that order of severity. It seems probable that atrophy of the stria vascularis causes some deficiency in the quality of endolymph throughout the cochlear duct, regardless of the location of the atrophy. Typically all other structures of the cochlear duct are normal, and the sense organ when stimulated within its sensitivity range is capable of normal stimulus coding, thus accounting for the usually excellent speech discrimination.     

Use of mixed anhydrides for the determination of terfenadine in dosage forms and spiked human plasma

Terfenadine reacts with mixed anhydrides (malonic and acetic anhydrides) producing a yellow-coloured product with intense fluorescence. Based on this fact, a spectrophotometric method was developed for the determination of terfenadine in dosage forms. The relation between the absorbance at 395 nm and the concentration is rectilinear over the range 0.5-5 microg ml(-1) (molar absorptivity is 1.405 x 10(5) l mol(-1) cm (-1)). The reaction product was also measured spectrofluorimetrically at 435 nm after excitation at 395 nm. The fluorescence intensity was directly proportional to the concentration over the range 0.5-4 ng ml(-1) with minimum detectability (S/N = 2) of 0.07 microg ml(-1) (approximately 1.5 x 10(-10) M). The different parameters affecting the development and stability of the reaction product were carefully studied and incorporated into the procedure. The proposed spectrophotometric method was successfully applied to the determination of terfenadine in tablets and suspensions; the percentage recoveries were 99.83 +/- 0.75 and 99.65 +/- 0.83, respectively. The proposed spectrofluorimetric method was applied to the determination of terfenadine in spiked human plasma. The percentage recovery was 99.35 +/- 2.19. The method is highly sensitive and specific. No interference was noticed from co-formulated drugs, such as pseudoephedrine and ibuprofen.     

Causes of elevated perilymph protein concentrations

Fifty-seven of 800 human temporal bones were found to have eosinophilic perilymph precipitates. The most common etiological factor was blockage of the internal auditory canal (20 cases). Acute bacterial labyrinthitis (nine cases) and subarachnoid hemorrhage (five cases) were also associated with perilymph precipitates. Small amounts of precipitate were also observed in 20 of 110 temporal bones without evidence of ear pathology. Experimental introduction of serum proteins into the cat's perilymphatic space confirms that eosinophilic perilymph precipitates may represent increased quantities of protein in the perilymphatic spaces; however, no correlation could be made between the quantity of precipitate observed and the concentration of the protein in the perilymph. The finding of increased perilymph protein above 1,000 mg/100 ml during a diagnostic inner ear tap (labyrinthotomy) is good evidence for the presence of an acoustic neurinoma. An associated peripheral VIIth never paralysis should alert the clinician to the possibility of a metastatic carcinoma of the internal auditory canal.     

Spectrofluorometric determination of montelukast in dosage forms and spiked human plasma

The native fluorescence of montelukast has been studied under different experimental conditions. The highest fluorescence intensity was obtained in methanol at 390 nm using 340 nm for excitation. Surfactants and sensitizers had either a negative or a slightly positive effect on its fluorescence intensity. The fluorescence intensity-concentration plot was rectilinear over the range 0.125 to 5 microg/ml with a lower detection limit of 0.02 microg/ml (3.4 x 10(-8) M). Interference likely to be introduced from co-formulated drugs (such as loratadine) or co-administered drugs (such as verapamil, carbazepam, propranolol) or other common drugs, was studied. The method was successfully applied to the determination of the drug in tablets (pediatric tablets, chewable tablets and adult tablets). The mean % recoveries were in agreement with those provided by the manufacturer. The method was further applied to the in vitro determination of montelukast in spiked human plasma, the mean % recovery (n = 5) was 100.08 +/- 1.40.     

Adsorptive stripping voltammetric behaviour of azomethine group in pyrimidine-containing drugs

The stripping voltammetric behaviour of buspirone hydrochloride (BUS) and piribedil (PIR), as models of pyrimidine-containing compounds, was studied using a hanging mercury drop electrode (HMDE). A sensitive adsorptive stripping voltammetric method for determination of such drugs is described. The voltammetric peaks were obtained at -1.23 and -1.22 V for BUS and PIR. respectively, which correspond to the reduction of the azomethine group of pyrimidine ring in Britton-Robinson buffer (pH 7). Factors such as pH of supporting electrolyte, accumulation potential and time and instrumental parameters were optimized. Calibration plots and regression data validation, accuracy, precision, limits of detection, limits of quantification, and other aspects of analytical merit are presented. The applicability of the method was evaluated through determination of BUS and PIR in tablet dosage forms. A preliminary study of the analysis of plasma samples, spiked with the investigated drug, after a simple extraction procedure is described.     

Spectrofluorimetric determination of manzamine A in spiked human urine and plasma

The native fluorescence of manzamine A (a biologically active beta-carboline marine-derived alkaloid) has been studied under different conditions. The highest fluorescence intensity was obtained in methanol. Two wavelength settings were found to be suitable for excitation, 280 nm and 340 nm; while lambdamax emission was constant in both cases at 387 nm. The fluorescence intensity at 340/387 nm setting was 1.6 greater than that obtained at 280/387 nm settings. The calibration curves were rectilinear over the range 0.1-2.0 and 0.5-2.5 microg/ml for the two settings, respectively. The detection limits were 0.05 microg/ml (9.1 x 10(-9) M) and 0.1 microg/ml (1.82 x 10(-8) M) at 340/387 nm and 280/387 nm, respectively. The proposed method was applied to the determination of manzamine A in spiked human urine and plasma samples adopting the 340/387 nm wavelength setting, the % recoveries (n = 6) were 99.61 +/- 0.90 and 100.25 +/- 1.63, respectively.     

Voltametric determination of vancomycin in dosage forms through treatment with nitrous acid

Two methods are described for the determination of vancomycin (vancomycin hydrochloride, CAS 1404-93-9) in its dosage forms. The two methods involve a prior treatment with nitrous acid then measuring the formed nitroso derivative, either spectrophotometrically or polarographically. In the spectrophotometric method, the absorbance-concentration plot is rectilinear over the range of 4-32 micrograms/ml with minimum detectability of 2.7 micrograms/ml (1.8 x 10(-6) mol/l). The apparent molar absorptivity is 4.084 x 10(-4)l.mol-1.cm-1 and A (1%, 1 cm) is 275. The reaction product was also found to be polarographically reducible at the Dropping Mercury Electrode (DME) with E1/2 of-0.9 V vs. Ag/AgCl electrode and a diffusion current constant (Id) of 0.85 +/- 0.02. The cathodic current produced was found to be diffusion controlled with some adsorption contribution. The calibration plot was linear over the range of 0.015-0.06 mmol l-1 for direct current (DCt) mode and from 0.005-0.05 mmol l-1 for differential pulse polarography (DPP) mode with minimum detectability of 2.4 x 10(-7) mol l-1 using the latter technique. The results obtained were statistically compared with those given with the official B.P. method and were in good agreement.     

Determination of the antiepileptics vigabatrin and gabapentin in dosage forms and biological fluids using Hantzsch reaction

A selective and sensitive method was developed for the determination of the anticonvulsants vigabatrin (I) (CAS 60643-86-9) and gabapentin (II) (CAS 60142-96-3). The method is based on the condensation of the drugs through their amino groups with acetylacetone and formaldehyde according to Hantzsch reaction yeilding the highly fluorescent dihydropyridine derivatives. The yellowish-orange color was also measured spectrophotometrically at 410 nm and 415 nm for I and II, respectively. The absorbance-concentration plots were rectilinear over the ranges 10-70 micrograms/ml and 20-140 micrograms/ml for I and II, respectively. As for the fluorescence-concentration plots, they were linear over the ranges 0.5-10 micrograms/ml and 2.5-20 micrograms/ml with minimum detection limits (S/N = 2) of 0.05 microgram/ml (approximately 2.1 x 10(-8) mol/l) and 0.1 microgram/ml (approximately 5.8 x 10(-7) mol/l) for I and II, respectively. The spectrophotometric method was applied to the determination of I and II in their tablets. The percentage recoveries +/- SD (n = 6) were 99.45 +/- 0.13 and 98.05 +/- 0.53, respectively. The spectrofluorimetric method was successfully applied to the determination of I and II in spiked human urine and plasma. The % recoveries +/- SD (n = 5) were 98.77 +/- 0.29 and 98.39 +/- 0.53 for urine and 99.32 +/- 0.74 and 98.90 +/- 0.96 for plasma, for I and II, respectively. No interference was encountered with the co-administered drugs: valproic acid (CAS 99-66-1), diphenylhydantoin (CAS 57-41-0), phenobarbital (CAS 50-06-6), carbamazepine (CAS 298-46-4), clonazepam (CAS 1622-61-3), clobazam (CAS 22316-47-8) or cimetidine (CAS 51481-61-9). A proposal of the reaction pathway is suggested. The advantages of the proposed methods over existing method are discussed.     

LC determination of dinitrosopiperazine in simulated gastric juice

A simple and specific reversed phase HPLC method for the determination of dinitrosopiperazine in simulated gastric juice using UV detection was reported. The chromatographic resolution of the analyte and the internal standard isosorbide dinitrate was performed without extraction from the gastric juice on a reversed phase ODS column. Isocratic elution was carried out with methanol–0.02 M sodium dihydrogen phosphate (60:40 v/v, pH 3.0) at a flow rate of 1.0 ml min⁻¹ with UV detection at 238 nm. The calibration graph was linear over the concentration range 0.072–2.88 μg ml⁻¹ of dinitrosopiperazine with minimum detectability (S/N=2) of 0.01 μg ml⁻¹ (8×10⁻⁸ M). Inter-day and intra-day precisions calculated as% RSD were in the range 0.32–0.38% and 0.19–0.25% respectively. Inter-day and intra-day accuracies calculated as% error were in the range 0.18–0.21 and 0.08–0.11% respectively. The proposed method was successfully applied to the study of the possible in–vivo production of DNPZ under the standard nitrosation conditions recommended by WHO.