Voltammetric quantification of anti-hepatitis drug Adefovir in biological matrix and pharmaceutical formulation

Electrochemical reduction behavior of Adefovir was studied using Hanging Mercury Drop Electrode (HMDE) in Britton-Robinson (BR) buffer solution.Voltammetric study showed one well-defined reduction peak in the potential range -1.2 to -1.4 V (vs.Ag/AgCl) due to reduction of C=N bond of the imidazole ring.Solid-phase extraction and protein-precipitation techniques were employed for extraction of Adefovir from human plasma.The proposed method allows quantification of Adefovir in human plasma over the concentration range 0.50-5.00 μg/mL with the detection limit 0.17 μg/mL,whereas in pharmaceutical formulation 0.25-2.25 μg/mL with the detection limit 0.08 μg/mL.

Evaluation of physicochemical properties as supporting information on quality control of raw materials and veterinary pharmaceutical formulations

This study aimed to show that the physicochemical proprieties obtained by Fourier transform infrared spectroscopy （FTIR）, thermogravimetry （TG）, and scanning electronic microscopy （SEM） can be useful tools for evaluating the quality of active pharmaceutical ingredients （APIs） and pharmaceutical products. In addition, a simple, sensitive, and efficient method employing HPLC-DAD was developed for simulta- neous determination of lidocaine （LID）, ciprofloxacin （CFX） and enrofloxacin （EFX） in raw materials and in veterinary pharmaceutical formulations. Compounds were separated using a Gemini Cm （250 mm×4.6 mm, 5μm） Phenomenex column, at a temperature of 25℃, with a mobile phase containing 10 mM of phosphoric acid （pH 3.29）： acetonitrile （85.7：14.3, v/v） and a flow rate of 1.5 mL/min. Physicochemical characterization by TG, FTIR, and SEM of raw materials of LID, CFX, and EFX provided information useful for the evaluation, differentiation, and qualification of raw materials. Finally, the HPLC method was proved to be useful for evaluation of raw material and finished products, besides satisfying the need for an analytical method that allows simultaneous determination of EFX, CFX, and LID, which can also be extended to other matrices and applications.

Sequential Injection Analysis of Ampicillin in Pharmaceuticals by Using Potentiometric Detectors Based on PVC and Sol-Gel Membranes

This work describes the construction and the evaluation of the general performance of new ampicilli-nate-selective electrodes based on manganese (III) tetraphenylporphyrin [Mn(III) TPP-Cl] as ionophore, incorporated in both PVC and sol-gel membranes and directly applied onto a conductive graphite/epoxy resin support. The units were constructed without inner reference solution adopting conventional configuration and in the case of PVC membrane the tubular configuration was also adopted. The good working characteristics of these electrodes, made possible its application to the determination of ampicillin in pharmaceuticals formulations, both in conventional batch analysis and in flow conditions, when the electrodes were coupled to a SIA system. In the last case the potentiometric sensors presented linear response towards ampicillin concentration between 5.0 × 10–4 and 5.0 × 10–2 mol?l–1 with slopes of –57.4 and –63.5 mV?dec–1 for the PVC and sol-gel membranes, respectively. The developed procedures enable mean relative standard deviations better than 3% for all the samples analysed. The obtained results do not statistically differ from those furnished by applying the HPLC reference method.

Chemiluminescence Determination of Benzoic Acid Using A Solid-Phase Verdigris Reactor

A new chemiluminescence flow system has been developed for sequential determina-tion of benzoic acid based on the reaction of the compound with copper carbonate entrapped in a solid-phase reactor. It was found that the unsaturated complex of Cu(II) and benzoic acid (1:1) has strong catalytic effect on the luminol-H2O2 chemiluminescence reaction. The calibration graph is linear over the range of 0.025 ~ 60 g/mL of benzoic acid, with a relative standard deviation of less than 3.0 %, and the detection limit is 0.01礸穖L-1. The proposed method was applied to the determination of benzoic acid content in different pharmaceutical formulations.

Spectrophotometric methods for the determination of gemifloxacin in pharmaceutical formulations

This paper describes two simple spectrophotometric methods for the determination of the antibiotic gemifloxacin mesylate(GFX)in pharmaceutical formulations.The first(A)is an indirect method in which oxidation of the drug with a known excess of cerium(IV)sulphate is followed by determination of the residual oxidant by adding excess methyl orange and measuring residual dye at 507 nm.The second(B)is a derivatisation method involving reaction of GFX with 1,2-naphthoquinone-4-sulphonate(NQS)in alkaline medium(pH 11)to form an orange-coloured product exhibiting maximum absorption(lmax)at 411 nm.The methods were linear in the concentration ranges 2–9 and 5–30 mg/mL for methods A and B,respectively,with intra-day precision(as RSD)o1.5%for both.When applied to the determination of GFX in pharmaceutical tablets,the results were in good agreement with those obtained by capillary electrophoresis.The two methods are useful for routine analysis of GFX in quality control laboratories.

Fabrication of the electrochemically reduced graphene oxide-bismuth nanoparticles composite and its analytical application for an anticancer drug gemcitabine

The present study explores an electroreduced graphene oxide-bismuth nanoparticles composite（ErGOBi） as an electrochemical sensor for the determination of an anticancer drug, gemcitabine hydrochloride（GMB）. The Er-GOBi interface was prepared by drop casting of bismuth nitrate-graphene oxide suspension on a glassy carbon electrode（GCE） followed by electro-reduction in the potential range of 0.6 V to 1.7 V. SEM, FTIR, EDAX and AFM techniques were employed for the characterization of prepared materials. Cyclic voltammetric and electrochemical impedance spectroscopic methods were used to understand the charge transfer properties of stepwise modification of Er-GOBi/GCE. GMB exhibited an irreversible oxidation peak at 1.144 V on Er-GOBi/GCE in phosphate buffer of p H 3. A 100-fold enhanced oxidation peak current was observed at Er-GOBi/GCE when compared to that at bare GCE.Sensing performance of Er GO-Bi/GCE was optimized by varying peak current dependent parameters.Linear relationship between the peak current and concentration of GMB was observed in the range of 0.1–51.1 mmol/L in differential pulse voltammetric method and 2.1–61.1 mmol/L in linear sweep voltammetric method. The practical utility of the proposed sensor, Er-GOBi/GCE was demonstrated by determining GMB in pharmaceutical formulations and spiked urine samples.

Effect of foreign ions for the determination of metal ion in the presence of surfactants

Aluminum is the third most abundant metal in the Earth’s crust.Despite its ubiquitous nature it is present in small amount in living organisms.Aluminum toxicity has been implicated in the pathogenesis of renal distinct clinical syndromes,including progressive and fatal encephalopathy and bone diseases.In the present study,Al was selected for the analysis by complexometric method.This method was based on the formation of a red colored ternary complex by the reaction of Aluminum with Aluminon(Aurin tricarboxylic acid triammonium salt)in the presence of micellar medium.The ternary complex of Aluminum with the surfactant Triton X-100 shows a maximum absorbance at 530 nm wavelength at pH 4.0 while with the sodium dodecyl sulfate it shows a maximum absorbance at 525 nm and at pH 5.0.The reaction was proceeded by the variation in pH and concentrations of surfactants,aluminon,aluminum.Their effects on the reaction of aluminum with aluminon complex in micellar media were recorded by UV-visible spectrophotometer.The reaction was found to be extremely rapid at room temperature.The system obeys Lambert Beer’s law between 0.24 and 21.74μg/mL concentrations with Triton X-100.The values of slope,intercept and correlation coefficients were 0.07,0.348 and 0.989,respectively.The concentration varied between 0.24 and 24.14μg/mL with sodium dodecyl sulfate and the values of slope,intercept and correlation coefficients were 0.029,0.148 and 0.962,respectively.The foreign ion effect was also tested by keeping the constant concentration of metal ion and determining its concentration in the presence of different foreign ions.The method was also applied for the determination of Al(III)in pharmaceutical formulations and water samples,which showed an excellent resemblance between reported and obtained results.