Adsorptive stripping Voltammetric determination of irbesartan using a hanging mercury drop electrode (HMDE) is described. The method is based on adsorptive accumulation of the species at the HMDE, followed by a first-harmonic alternating current (AC) stripping sweep at pH 6. The behavior of the adsorptive stripping response was studied under various experimental conditions, e.g., type of supporting electrolyte, pH, accumulation time, scan rate, and mode of sweep. In Britton-Robinson buffer solution, a quasi-reversible reduction process involving transfer of two electrons and two protons takes place. The response was linear over the concentration range of 0.16 -1.60 mg/ml with regression coefficient 0.997 and detection limit 0.11 mg/ml. The average of determinations of the cited compound in oral dosages with its standard deviation was 99.39 ± 4.33 %.The result obtained by the proposed method was compared with that obtained by the uv-spectrophotometric technique. Furthermore, the proposed method was also successfully applied as a stability-indicating method.

Cathodic stripping voltammetric determination of losartan using hanging mercury drop electrode HMDE was described. The method was based on adsorptive accumulation of the species at HMDE and at pH 7, followed by alternating current AC sweep. The behavior of adsorptive stripping response was studied under various experimental conditions, e.g. type of supporting electrolyte, pH, accumulation time, scan rate and mode of sweep (direct current DC, differential pulse DP, square wave SW and AC). In Britton-Robinson buffer solution, pH 7, a quasi-reversible reaction took place. The reduction response was more sensitive than the oxidation one and it was linear over the concentration range of 0.16-1.2 µg/mL. The determination of the cited compound in oral dosages was achieved using the standard addition method. The average of determinations obtained by square wave adsorptive voltammetric method with its standard deviation was 100.1±3%.

Carbon paste electrode modified with zinc oxide nano particles immobilized on multi-walled carbon nano tubes (MWCNTs/ZnO-NPs/CPE) was exploited for the simultaneous determination of Desvenlafaxine succinate (DVS) and Clonazepam (CLZ) in drug substance and combined drug products as well as in spiked human urine. The electrochemical response characteristics of the modified electrode toward DVS and CLZ were investigated by cyclic and differential pulse voltammetry (CV and DPV). The cyclic voltammograms showed well defined, irreversible cathodic peaks (reduction) at potential around −407 and −636 mV in Britton-Robinson (BR) buffer (pH 9.0) for DVS and CLZ, respectively. Different experimental factors affecting the method sensitivity have been investigated and optimized including pH of supporting electrolyte, electrode modifiers, different surfactant and scan rate. A good linear relationship was obtained between the peak current and the concentration within the range of 0.66-8.42 μg/mL and 0.39-7.70 μg/mL for DVS and CLZ, respectively using DPV method. The proposed method was successfully applied for the estimation of DVS and CLZ in its combined dosage form and in spiked human urine. The results obtained were validated according to ICH guideline and were found to be in agreement with those obtained by the reference HPLC methods.

Gold nanorods (NRs) have attracted a great deal of interest for a variety of biomedical and sensing applications. However, developing robust methods for biofunctionalizing NRs has continued to be challenging, especially for NR-DNA conjugates. This is due to the presence of cetyltrimethylammonium bromide (CTAB), which plays an essential role in controlling the anisotropic particle growth. In this article, we systematically explore the growth of a polydopamine (PDA) layer on a range of NR surfaces, comparing different polyelectrolyte and alkanethiol coatings as well as direct CTAB displacement. This revealed that the PDA layer thickness and growth rate is strongly dependent on the underlying nanorod functionalization chemistry and allowed us to establish a preferred route for the creation of stable, non-aggregated suspensions of PDA-coated NRs. The utility of this platform was then demonstrated by self-assembling packed monolayers of single-stranded DNA on the outer surface. Both the surface attachment and bioactivity of the resulting NR-DNA conjugates was then demonstrated by performing bulk solution and single nanoparticle imaging fluorescence measurements.

[a] 1Introduction Strontium Ranelate (SR)i sc hemically known as 2-(2-Carboxy-4-cyano-5-[N,N-di(carboxymethyl)amino]thiophen-3-yl) acetic acid distrontium salt [1,2].S Ri st he only anti-osteoporotic agent which both increases bone formation and reduces bone resorption, resulting in ar ebalance of bone turnover in favor of bone formation.S R is given orally in the treatment of postmenopausalo steoporosis to reduce the risk of vertebral and hip fractures [1,2].V ery few analytical techniques appeared in the literature for the determination of SR in pharmaceutical formulations.T he methods so far reported include high performance liquid chromatography HPLC with UV detection [3],s tability indicating assay studies usingR P-HPLC were also conducted [ 4,5],U Vs pectrophotometry [6,7] and capillary zone electrophoresis [8].A lso,s ome methods utilized the strontium ions for determinationo f the drug such as atomic absorption spectrophotometry AAS [9] and electrochemical detection of strontium throughi nteraction with metallothionein [10].To our knowledge,n ov oltammetric methods for the direct determination of SR have been reported. Hence, the current electroanalyticalr esearch aimed to study the DP and SW voltammetric behavior of SR in its pure and pharmaceutical dosage form. Thee lectroanalytical technique provides the advantages of simplicity,h igh sensitivity,l ow cost, relatively short analysis time and direct analysis,w ithout any derivatization, extraction or clean-up steps [11,12]. Materialsa nd ReagentsAll reagentsa nd solvents were of analytical reagent grade and used without further purification. Pure Sample and Commercial DosageF ormSR of purity 98 %: manufactured by Les laboraroires Servier Industrie -F rance.Thep harmaceutical preparation Protelos ,2 gS Rs achets:( Batch No.870544, Manuf.B yLes laboraroires Servier Industrie -F rance, Packed by Servier Egypt IndustriesL imited -6 th OctoberC ity -E gypt) wasp urchased from the local market. ReagentsBritton Robinson (BR) buffer 0.04 M, wasp repared by mixing the acid mixture containing0 .04 Mp hosphoric acid, 0.04 Ma cetic acid and 0.04 Mb oric acid [13].B uffer solutionsw ere adjusted with the appropriate amount of 0.2 Ms odium hydroxide to get the desired pH in the Abstract:T he voltammetric behavioro fS trontium Ranelate (SR) was studied using Cyclic (CV),d ifferential pulse (DPV)a nd square wave (SWV) voltammetry.C V showed twow ell-defined, irreversible,d iffusion-controlled anodicp eaks usingB ritton-Robinsonb uffer, pH 2.0 at Pencil graphite (PGE), Carbon paste (CPE) and glassy carbon (GCE)e lectrodes.T he peak currentconcentrationr elationship was rectilinearo ver the range 1.0-10.0, 1.0-11.25 and 2.5-24.0 mg/mL at PGE,C PE and GCE respectively,w ith am inimum detectability of 0.17, 0.24a nd 0.39 mg/mL for peak 1a nd 0.19,0 .27 and 0.51 mg/ mL for peak 2. Recoveries showed the high accuracy of the method; 99.8 %, 99.5 %a nd 99.7 %a tP GE, CPE and GCE respectively for peak 1a nd 100.1 %, 99.9 %a nd 99.7 %a tP GE, CPE and GCE respectively for pe...