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Cefpirome, which is a fourth-generation cephalosporin, was analyzed for the first time at a glassy carbon electrode using differential pulse voltammetry in this novel method. Different experimental conditions were optimized, such as pH and electrolyte type, to achieve a high peak current. Under the optimum conditions, the oxidation of cefpirome exhibited diffusion-controlled process depending on pH. Cefpirome was electrochemically determined at the linear range between 2-200 µM, and the detection limit was found as 0.167 µM in pH 4.7 acetate buffer solution. Analysis results showed that the proposed electrochemical method could be used for the determination of cefpirome in human urine samples. A linear relationship has been obtained in the concentration range of 2-10 µM. At the same time, the detection limit was found as 0.101 µM for cefpirome in human urine. Moreover, to check the selectivity of the proposed method, the effect of some interference species, including ascorbic acid, uric acid, dopamine, glucose, 〖"Na" 〗^"+" , "K" ^"+" , 〖"Ca" 〗^"+2" , 〖"NO" 〗_"3" ^"-" , have also been investigated. As a result, a simple, sensitive, reproducible, no time-consuming, and more environmentally friendly method was developed when compared to the literature studies.

Carbon-Based Composite Materials for Electrodes is a new open Special Issue of Materials, which has the goal of publishing original research and review articles focused on carbon nanotubes, graphene, activated carbon, graphite, pencil graphite, graphene oxide, graphene nanoplatelets, pyrolytic graphite, organic mass derived carbon, fullerenes, diamond, glassy carbon, carbon fibers, and other composites for electrode preparation and its applications [...]

Fixed dose combinations of ezetimibe and rosuvastatin are well known to provide significantly superior efficacy to rosuvastatin alone in lowering total cholesterol, and triglyceride levels. Therefore, in this recent work, we prepared fixed dose (10mg/10mg) ezetimibe and rosuvastatin tablet formulations, and a simple, selective and we established and validated rapid chromatographic method for the sensitive and simultaneous determination of rosuvastatin and ezetimibe. We performed the separation on Zorbax SB-C18 (100 mm x 4.6 mm, 3.5 µm particle size) column at 30 oC with a mobile phase that has a composition as water containing 0.1% H3PO4:methanol:acetonitrile (50:25:25 v/v/v) at 1.2 mL/min flow rate. We further performed validation studies according to ICH guidelines. Furthermore, we exposed rosuvastatin and ezetimibe to degradation conditions. We plotted peak area vs. concentration graphs for rosuvastatin and ezetimibe and used for defining the linearity of the detector response. In this suggested method, we observed linear relationships varying from 0.05 to 50 µg/mL for ezetimibe concentrations and from 0.05 to 25 µg/mL for rosuvastatin concentrations. We found the limit of detection values for rosuvastatin and ezetimibe as 0.006 and 0.008 µg/mL, respectively. Moreover, we further used the established method for to the analysis of ezetimibe and rosuvastatin from real spiked samples of rabbit serum.

In this study, the interaction between the phosphodiesterase-3 enzyme inhibitor drug milrinone and biomolecules was investigated by electrochemical, fluorescence spectroscopy, and molecular docking studies for the first time. The interaction between milrinone and biomolecules was investigated according to the decrease in deoxyguanosine oxidation signals of milrinone and calf thymus double-stranded deoxyribonucleic acid (ct-dsDNA) by cyclic voltammetry and differential pulse voltammetry. In fluorescence spectroscopy studies, a competitive study was conducted on ct-dsDNA by adding a well-known fluorescent methylene blue and ct-dsDNA solution. The fluorescent results showed that milrinone had a higher affinity for ct-dsDNA binding compared to methylene blue. Interaction studies show that milrinone binds to ct-dsDNA via a groove-binding mode, and the binding constant values ​​were calculated as 4.27 × 106 M−1 and 6.03 × 104 M−1 at 25 °C, based on cyclic voltammetry and spectroscopic results, respectively. As a result of the interaction of human serum albumin and milrinone, the binding coefficient was calculated as 4.11 × 106 M−1 by cyclic voltammetry. In addition, experimental results were confirmed by obtaining information about the possible spatial structure of the aggregate formed through theoretical calculations based on energy minimization for milrinone- ct-dsDNA and milrinone-human serum albumin mixtures with molecular insertion.

Combined therapy for HIV treatment shows superior efficacy in comparison to single therapy. Furthermore, the separation and determination of the combined dosage forms hold a significant place in the pharmaceutical industry. Not only reverse phase high-performance liquid chromatography (HPLC) but also hydrophilic interaction liquid chromatography (HILIC) can be used for these purposes. Contrary to conventional RP systems, HILIC may be an alternative for the analysis of polar substances. The aim of this study was the step-by-step development of a simple, rapid, and reliable method for the simultaneous determination of antiviral compounds from their marketed formulation (Trizivir). In order to achieve this goal, various mobile phase systems, buffer types, and concentrations were prepared to provide an appropriate separation. Different types of columns were tested to find the best resolution and high efficiency for the studied compounds. The proposed method provided a simple procedure for the simultaneous analysis of abacavir, lamivudine, and zidovudine in their pharmaceutical preparation within approximately 2 min using the conventional HPLC system. The developed method was fully validated according to the International Council for Harmonisation guidelines from the viewpoint of selectivity, sensitivity, precision, accuracy, linearity, limit of detection, and quantification.

This paper demonstrates a Schiff base i. e. 5-(diethylamino)-2-((2,6-diethylphenylimino)methyl)phenol (5-DDMP) that was sensed by DNA biosensor. dsDNA was immobilized onto GCE modified with functionalized multi-walled carbon nanotubes to prepare a biosensor. The efficiency of dsDNA biosensor was determined and binding of 5-DDMP with dsDNA was searched by UV-vis spectrophotometry and differential pulse voltammetry. Molecular docking simulations between 5-DDMP and dsDNA were explored and as a result, a hydrogen bond and a pi-pi contact were observed between 5-DDMP and deoxyguanosine base (dG22) of the strand B, deoxyadenosine base (dA5) of the strand A, respectively. These studies could be useful for new anticancer drug design and development.

A new capillary electrophoresis method has been developed to analysis of paracetamol (PAR), caffeine (CAF) and codeine (COD) phosphate from pharmaceutical dosage forms. Good results were obtained by using a background electrolyte solution consist of 25 mM (pH 8.5) phosphate buffer solution containing 10% methanol. The separation was performed through an uncoated fused-silica capillaries (50 mu m internal diameter, 56 cm total length, 47.5 cm effective length) at 25 degrees C with the application of 10 seconds of hydrodynamic injection at 40 mbar pressure and a potential of 27 kV. Detection wavelength was chosen 210 nm. Under optimum conditions, the migration times were found 4.427 min for PAR, 3.952 min for CAF, and 3.253 min for COD-phosphate. Linearity ranges were determined 99.72 - 1994.40 mu g mL(-1) for PAR, 5.75 - 115.04 mu g mL(-1) for CAF and 1.84 - 36.80 mu g mL(-1) for COD-phosphate for the method. Limit of detections were found 0.724 mu g mL-1 for PAR, 0.533 mu g mL(-1) for CAF and 0.263 mu g mL(-1) for COD-phosphate in this study. Also, limit of quantitations were found 2.415 mu g mL(-1) for PAR, 1.776 mu g mL(-1) for CAF and 0.877 mu g mL(-1) for COD-phosphate. According to the obtained results, the method is sensitive, specific and repeatable to analysis of PAR, CAF and COD-phosphate.

The voltammetric behavior of the vardenafil was investigated by means of square wave stripping voltammetry (SWSV), differential pulse stripping voltammetry (DPSV) and cyclic voltammetry (CV) on the modified electrodes constructed by graphite, metal oxide and functionalized multi-walled carbon nanotubes (MWCNT).Different experimental conditions were optimized such as pH and electrolyte type, accumulation potential and accumulation time for both techniques and step potential, pulse amplitude and frequency for SWSV. In the optimum conditions a linear relationship has been constructed in the concentration range of 0.02 to 1.0 mg/L and 0.01 to 0.5 mg/L for SWSV and DPSV in pH 3.0 phosphate buffer solution, respectively. Limit of detection (LOD) values for vardenafil determinations were13.6 mu g/L and 4.38 mu g/L for SWSV and DPSV, respectively. Quantifications were performed on commercial pharmaceutical tablets and synthetic blood serum using both techniques. The relative errors were +5.0% and -3.0% for SWSV and DPSV, respectively in the determination of vardenafil active ingredient in Levitra (R) tablet. SWS and DPS voltammetric determination of synthetic blood serum spiked with 50.0 mu g/L vardenafil exhibited 100.8% and 104.4% recovery, respectively. Interference effects of some organic species such as ascorbic acid, uric acid, dopamine, glucose have also been investigated.

Dienogest (DGN), is an orally administered synthetic progestin that has shown to have selective progesterone receptor (PR) agonistic activity and oral progestational potency on endometrium. In this paper, the investigation of electrochemical reduction of Dienogest on dropping mercury electrode (DME) is achieved and resulted in a reduction scheme that involves a two electron reduction of 3-keto-delta-4-group in the A-ring of the molecule. This observation is supported by comparison of the compound with model compounds of testosterone and norethisterone. In this study, electrochemical determination of the compound and its validation is also studied by differential pulse polarograhy (DPP). The results yielded good precision, accuracy and reproducibility. Calibration range was found as 2.00 × 10-6M to 1.00 × 10-4M, with LOD and LOQ values as 0.58 × 10-6M and 1.90 × 10-6M, respectively. © 2018 The Electrochemical Society.

The development of agriculture is closely related to the use and application of pesticides in order to improve products. Excessive use of pesticides is indeed very dangerous to essential pests and it has a potential negative effect over human health, pollution of soil and waters. For these reasons, in this study, a dilute-and-shoot sample preparation procedure for simultaneous determination of three pesticides (buprofezin, dinobuton and chlorothalonil) was developed and validated for the first time combined with high-performance liquid chromatography–diode-array detector method in urine, serum, tomato, soil, commercial dosage form and water samples. Also, the degradation and behaviour of these pesticides were investigated under different conditions in the environment. HPLC analysis was performed with Kinetex C18 (150 mm × 4.6 mm; 5 μm) column with 1 mL min−1 flow rate of mobile phase which consisted of acetonitrile/buffer in the ratio of 75:25 (v/v) at 25.0°C. Calibration graphs showed a good linearity with a coefficient of determination (R2) of at least 0.999 for all analytes. Intraday and interday precisions (expressed as RSD%) were lower than 1.66% for all analytes. The developed method was demonstrated to be sensitive, simple, robust and rapid for the simultaneously determination of analytes in different samples providing recoveries in the range between 92.3% and 109.74%.

In the present work, the electrochemical oxidation of a new generation of anticancer drug, imatinib ( Ima ), using differential pulse voltammetry (DPV) on anodically pretreated boron doped diamond electrode (BDDE) has been reported. The results of a study showed that Ima provided well-shaped oxidation peak at positive potential of around + 1.0 V ( vs. Ag/AgCl/KCl) in the Britton–Robinson (B–R) buffer at pH 2.0. The experimental conditions, i.e. pH, a modulation amplitude, a modulation time, a step potential, and a scan rate, were optimized. A simple, rapid, selective and sensitive DPV procedure for the determination of Ima was performed in the concentration range of 3.0 × 10 − 8 –2.5 × 10 − 7 mol L − 1 with the limit of detection ( LOD ) and the limit of quantification ( LOQ ) of 6.3 × 10 − 9 mol L − 1 and 2.1 × 10 − 8 mol L − 1 , respectively. The proposed methodology with using an anodic signal of imatinib at BDDE shown comparable detection limit as for hanging mercury drop electrode in the determination of this anticancer drug. A biological significance of the developed DPV procedure was demonstrated by a quantitative analysis of the spiked human urine samples with satisfactory recoveries (from 102.2% to 105.5%). Additionally, the influence of some interfering compounds and ions ( Int ) was also evaluated. The cyclic voltammetry (CV) was used for the investigation of the electrooxidation mechanism of Ima . The developed approach could be beneficial in analysis of imatinib in biological samples using BDDE as up-to-date electrochemical sensor and could represent non-toxic analytical alternative to HMDE.

In this study, we report the development of a sensitive label-free impedimetric sensor based on molecularly imprinted polymer (MIP) as biomimetic receptor coupled with screen-printed electrodes (SPEs) for the detection of vascular endothelial growth factor (VEGF). Firstly, electropolymerization of o-phenylenediamine (o-PD) in the presence of VEGF molecule by cyclic voltammetry was performed onto graphite screen-printed electrodes. The solvent extraction of the target was then carried out. The MIP based sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Using optimized experimental conditions, the single-use MIP-based sensor showed a good analytical performance for VEGF detection from 20 to 200 pg mL(-1) with limit of detection of 0.08 pg mL(-1). Finally, the developed MIP-based sensor in human serum samples was also tested.

In this experimental study, we developed lateral flow immunoassay strips for the detection of Escherichia coli. For labelling, gold nanoparticles were prepared and modified with a Raman label. As a result of this, not only colorimetric responses but also Raman responses were obtained from the same strips. The color and Raman intensities were employed for the quantitative determination of Escherichia coli. The employment of two different detection methods strengthens the quantitative determination of Escherichia coli by lateral flow immunoassay, which is mostly used for qualitative detection or sometimes the semi-quantitative determination of samples. After careful optimization and validation steps, the developed strips allowed the highly sensitive determination of Escherichia coli in water and urine samples.

A carbon paste electrode modified by –COOH functionalized multiwalled carbon nanotubes and Fe2O3 nanoparticles was prepared for the determination of antiparkinson drug ropinirole using adsorptive stripping differential pulse and square wave voltammetric methods. The results showed that the modified electrode significantly enhanced the oxidation peak current of ropinirole. Effects of pH, scan rate, and electrolyte type on the determination of ropinirole were analyzed. Ropinirole gave two irreversible anodic peaks at modified electrode in pH 6.0 phosphate buffer solution; studies were realized for the peak which was more positive potential (peak 2). Limit of detection values were 1.30 × 10−3 μg mL−1 and 4.08 × 10−4 μg mL−1 for peak 2 with adsorptive stripping differential pulse and square wave voltammetric methods, respectively. The proposed methods were applied to analysis of pharmaceutical dosage form containing ropinirole. The recovery studies with values of 105.50 and 100.88 % showed the accuracy of these methods. The number of transferred electrons was investigated.

Poly(acridine orange) was electropolymerised on glassy carbon electrodes by potential cycling in phosphate buffer solution at pH 5.5, 6.0, 7.0 and 8.0. Electrochemical behaviour of the modified electrodes was studied by cyclic voltammetry in phosphate buffer solution at various pHs and found that the best polymer film formation was obtained at pH 5.5. Quantitative determination of uric acid was achieved by cyclic voltammetry, differential pulse voltammetry (DPV) and fixed-potential amperometry in phosphate buffer solution at pH 5.5. Anodic peak currents were linearly proportional to concentration of uric acid in the range 1–75 µM for cyclic voltammetry, 0.4–75 µM for DPV and 0.04–5.3 µM for amperometry. Detection limits were 3.7 × 10−1, 9.7 × 10−2 and 9.5 × 10−3 µM for cyclic voltammetry, DPV and amperometry, respectively. The modified electrodes exhibited good sensitivity, wide linear range and good stability. There is no interference from substances commonly present in natural samples.

In this study, direct and sensitive determination of famotidine based on its electrochemical oxidation was investigated in spiked human urine and tablet dosage forms. The electrochemical measurements were carried out in various buffer solutions in the pH range of 0.88 to 12.08 at ultra trace graphite electrode (UTGE) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results were obtained for the quantitative determination of famotidine by DPV technique in 0.5 mol L-1 H2SO4 solution (pH=0.30). In this strong acid medium, one irreversible anodic peak was observed. The effect of pH and scan rate on the peak current and peak potential were investigated. The diffusion-controlled nature of the peak was established. For optimum conditions described in the experimental section, a linear calibration curve for DPV analysis was constructed in the famotidine concentration range 2 x 10-6 - 9 x 10-5 mol L-1. Limit of detection (LOD) and limit of quantification (LOQ) were 3.73 x 10-7 and 1.24 x 10-6 mol L-1 at UTGE respectively. Repeatability, precision and accuracy of the developed technique were checked by recovery studies in spiked urine and tablet dosage forms.

The aim of this study was to develop a reversed-phase high performance liquid chromatographic (RPHPLC) method for the simultaneous determination of quinapril (QNP) and hydrochlorothiazide (HCZ) in pharmaceutical dosage forms. In this method quinapril, hydrochlorothiazide and perindopril (internal standard) were separated using a reversed phase column (Hichrom C18; 250×4.6 mm i.d.; 10 µm) with acetonitrile: potassium dihydrogen phosphate (at pH 2.5; 0.067 M) (40:60 v/v) as a mobile phase. UV visible dedector set at 211 nm and mobile phase was pum-ped at 1.0 mL/min flow rate. The chromatographic separation was performed at 25 oC. In these conditions the re-tention times for quinapril, hydrochlorothiazide and perindoprile were 4.391, 3.237 and 3.931 min, respectively. Linearity was obtained in the concentration range of 2-30 µg/mL for quinapril and 1.25-18.75 µg/mL for hydrochlo-rothiazide. The proposed method has been fully validated and allows a number of cost- and time-saving benefits. It was successfully applied to the determination of QNP and HCZ in synthetic mixtures and in pharmaceutical dosa-ge forms. The proposed method is simple, rapid and suitable for quality control (QC) applications

The electrochemical oxidation of fulvestrant was made on highly boron-doped diamond electrode using differential pulse adsorptive stripping voltammetry. The highest current intensities were obtained by applying +1.10 V during 150 s for boron-doped diamond electrode. For boron-doped diamond electrode, linear responses were obtained for the concentrations between 1 × 10−6 and 8 × 10−5 M in standard samples and between 1 × 10−6 and 4 × 10−5 M in serum samples. The repeatability of the method was 0.55 RSD% for differential pulse adsorptive stripping voltammetry. The analytical values of the method are demonstrated by quantitative determination of fulvestrant in pharmaceutical formulations and human serum, without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances. Selectivity, reproducibility, and accuracy of the developed methods were demonstrated by recovery studies.

The electrooxidative behavior and determination of ciprofloxacin at a glassy carbon electrode were investigated using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. The dependence of the peak current and peak potentials on pH, concentration, nature of buffer, and scan rate were examined. The oxidation of ciprofloxacin gave a single and irreversible peak at glassy carbon electrode. The process was diffusion controlled. A linear response was obtained between 1.0 � 10 -6 and 4.0 � 10 -5 M in 0.1 M sulphuric acid for both techniques. The recovery studies were also achieved to check selectivity and accuracy of the methods. The proposed methods were applied for the determination of ciprofloxacin from pharmaceutical dosage forms without any time-consuming extraction, separation, adsorption steps. The repeatability, reproducibility, precision and accuracy of the proposed methods were investigated.

Compared to other voltammetric techniques a square wave voltammetry (SWV), which is presented in this minireview, has a several advantages such as high speed, increased analytical sensitivity and relative insensitivity to the presence of dissolved oxygen. Also it is an electrochemical technique used in analytical applications and fundamental studies of electrode mechanism. This paper delivers both the underlying theory and the practical guidance needed to apply square wave techniques and also provides a wide collection of data for the description of diverse tendencies that characterize several electrochemical reactions analyzed by SWV. This review summarizes some of the recent developments and application of direct and stripping SWV for drug compounds in their dosage forms and biological samples as reported in the period from 1997 till 2010 year.

Boron-doped diamond electrodes have received much attention for electrochemical determination due to their attractive electrochemical properties over other electrodes. The electrooxidation of fluvastatin sodium at boron-doped diamond electrode was investigated using cyclic, differential pulse and square wave voltammetry. The possible mechanism of oxidation was discussed with model compounds that have indole oxidation. The dependence of the peak current and potentials on pH, concentration, scan rate, and the nature of the buffer were investigated. The oxidation of fluvastatin was irreversible and exhibited a diffusion-controlled fashion. The slope of the log i p –log v linear plot was 0.44 indicating the diffusion control for pH 10.00 Britton–Robinson buffer solution. The linear response was obtained in the ranges of 1 × 10 − 6 M–6 × 10 − 4 M in pH 10.00 BR buffer solution. The detection limit of the standard solution is estimated to be 1.37 × 10 − 7 M for DPV, 1.44 × 10 − 7 M for SWV. The repeatability of the methods was found as 0.66 and 0.15 RSD % for peak currents for differential pulse and square wave voltammetry, respectively. The practical analytical value of the method is demonstrated by quantitative determination of fluvastatin in pharmaceutical formulation and human serum, without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances. Selectivity, reproducibility and accuracy of the developed methods were demonstrated by recovery studies.

The polarographic reduction of Co(II) in the presence of moxifloxacin (1-cyclopropyl-7-[(S,S)-2.8-diazabicyclo[4.3.0]non-8-yl]-6-fluoro-8-methoxy-1.4-dihydro-4-oxo-3-quinolinecarboxylic acid) gives rise to an additional adsorption peak corresponding to the reduction of Co(II)-moxifloxacin complex on the mercury drop electrode at -1.17 V. This new peak is applicable to Co(II) determination with the linearity proportional to the Co(II) concentration in the range of 4.93 x 10(-7) -6.90 x 10(-5) M and can be attributed to an adsorption-controlled process with an irreversible reduction. Without using moxifloxacin, the polarographic determination of 2.50 x 10(-6) M Co(II) is impossible under the given conditions due to very poor sensitivity at -1.38 V. The proposed method showed good precision and accuracy with a relative standard deviation of 3.01% and relative error of +6.40% for the determination of 2.50 x 10(-6) M Co(II) next to 5.0 x 10(-6) M of Zn(II), Ni(II), and Cd(II). The accuracy of the method was also checked by the determination of Co(II) spiked with tap water and certified sea water, and the percentage recoveries were 97.5 and 96.7%, respectively (n = 4 at 95% confidence interval).

A simple, accurate, precise and fully automated method for the simultaneous determination of abacavir, lamivudine and zidovudine in pharmaceutical tablets, human serum samples and drug dissolution studies has been developed. Separation was performed on a 5 μm Zorbax® C18 column (150 × 4.6 mm ID) with methanol:water:phosphate buffer at pH 5.65 (80:10:10; v/v/v) isocratic elution in less than 7 min with a flow rate of 0.6 mL min−1.Good sensitivity for all analytes was observed with UV detection at 275 nm. The method allowed quantitation over the 500–3,000 ng mL−1 range for abacavir and 500–5,000 ng mL−1 range for lamivudine and zidovudine. The method has been applied, without any interference from excipients or endogenous substances, for the simultaneous determination of these three compounds in tablets. Human serum and drug dissolution studies.

Ascorbic acid is the most common electroactive biological compound found in some plant species (e.g., Citrus species, Rosa species). The electrochemical oxidation of ascorbic acid was investigated by cyclic, linear sweep, differential pulse (DPV), and square wave (SWV) voltammetry. For analytical purposes, a very well-resolved diffusion-controlled voltammetric peak was obtained in acetate buffer at pH 3.50 for DPV and SWV. The linear response was obtained in the range of 3.52–176.1 μg/mL with a detection limit of 0.88 μg/mL for DPV and 0.52 µg/mL for SWV. Based on this study, simple, rapid, selective, and sensitive voltammetric methods were developed for the determination of ascorbic acid in pharmaceutical dosage forms and Rosa species (R. dumalis ssp. boissieri var. boissieri, R. canina, R. pulverulenta, R. heckeliana ssp. vanheurckiana, and R. montana subsp. woronowii). The results obtained are compared with the HPLC data. The developed methods enable the extracts to be analyzed without the necessity of any time-consuming separation.

In the present paper, rapid, sensitive, selective, accurate and precise analytical methodologies were developed for the determination of the antidepressant drug mirtazapine (MIR) using voltammetry and liquid chromatography. In cyclic voltammetry (CV), MIR showed one sharp oxidation peak and one additional wave in acidic media in the anodic direction; at pH 5.50, the mirtazapine peak was single and sharp. Under optimized conditions, the peak current showed a linear dependence with concentration in the range between 0.212 and 26.54 µg/mL for glassy carbon (GC) and 1.06 and 26.54 µg/mL for boron-doped diamond (BDD) electrodes using differential pulse (DP) and square wave (SW) voltammetric techniques. The possible oxidation mechanisms are also discussed. A simple and fully validated reverse phase-liquid chromatography (RP-LC) method to test for MIR in tablets was developed using an X-Select RP-18 column (250x4.60 mm ID x 5µm) at 25ºC with methanol:water (30:70, v/v, containing 15 mM o-phosphoric acid) as the mobile phase adjusted to pH 3.0. The RP-LC method allowed quantification over a MIR concentration range of 1.0-18.0 µg/mL. MIR was exposed to thermal, photolytic, or oxidative stress, as well as acid and base hydrolysis conditions, and the stressed samples were assayed by the proposed LC method. The proposed methods allow for a number of cost- and time-saving benefits.

Voltammetric, chromatographic, and spectrophotometric methods were developed for the simultaneous determination of bisoprolol fumarate (BIS) and hydrochlorothiazide (HCZ). Differential pulse and square wave voltammetry techniques were used to analyze BIS and HCZ simultaneously by measuring at about 1400 and 1100 mV, respectively. RP-HPLC was the second method for simultaneous analysis of the compounds. The mixture of BIS, HCZ, and moxifloxacin as an internal standard was separated on an RP Zorbax Eclipse XDB-C18 column (150 × 4.6 mm, id, 5 μm particle size) using acetonitrile–15 mM phosphate (25 + 75, v/v) mobile phase at a 1.0 mL/min flow rate. The third method was based on first derivative of the ratio-spectra method obtained from the measurements of the amplitudes at 246 and 257 nm for BIS and HCZ, respectively. All the proposed methods were effectively applied for the simultaneous determination of BIS and HCZ in tablet dosage forms without any time-consuming extraction, sample preparation, or derivatization procedures.

The interaction of Efavirenz (EFV) with fish sperm dsDNA immobilized onto pencil graphite electrode (PGE) has been studied by using differential pulse voltammetric technique using an electrochemical DNA biosensor. The guanine signal was lower with (double stranded-DNA) dsDNA-treated PGE than the untreated electrode after the interaction with EFV occurred. The changes in the experimental parameters such as the accumulation time and the concentration of EFV were also studied. All necessary parameters such as sensitivity, selectivity, accuracy and precision were calculated. In addition, the detection and determination limits, reproducibility and applicability of the analysis to pharmaceutical dosage forms were also investigated. These results showed that this DNA biosensor could be used for the sensitive, rapid simple and cost effective detection and determination of EFV-dsDNA interaction. The linearity was between 2 and 24 ppm of EFV concentration on guanine signal decreasing curve. EFV showed an irreversible oxidation behavior at all investigated pH values. This oxidation step was adsorption controlled on PGE. Hence, differential pulse adsorptive stripping (AdsDPV) voltammetric method was developed for the determination of EFV. Accumulation time and potential were optimized. Under these conditions, the current showed a linear dependence with concentration in the range between 0.018 and 2.56 ppm. Both determination methods were fully validated and applied for the analysis of EFV pharmaceutical dosage form.

The oxidation of fluvastatin sodium on a glassy carbon electrode has been studied by use of a variety of voltammetric techniques. Different conditions were investigated to optimize the determination of fluvastatin sodium. The dependence of the intensities of currents and potentials on pH, concentration, scan rate, and nature of the buffer was investigated. Oxidation of fluvastatin sodium was found to be diffusion-controlled and irreversible. The best results for the determination of fluvastatin sodium were obtained by using differential pulse and square-wave voltammetric techniques in Britton-Robinson buffer at pH 10.04. Differential pulse and square-wave voltammetry at a glassy carbon electrode resulted in linear calibration in the range 8x10(-6) to 6x10(-4) mol L(-1) and detection limits of 1.07x10(-6) and 7.99x10(-7) mol L(-1), respectively. The proposed methods were successfully applied to the determination of the drug in capsules and biological fluids. Excipients did not interfere with the determination. Statistical validation revealed that the methods were free from significant systematic errors.

Analytical methods including chromatographic methods are commonly used for the quantitative and qualitative analysis of raw materials, drug substances, drug products, and compounds in biological samples in pharmaceutical industry. The components monitored include chiral or achiral drugs, process impurities, residual solvents, excipients such as preservatives, degradation products, extractable and leachable from container and closure or manufacturing process, pesticide in drug product from plant origin, and metabolites. Validation of an analytical method which is used during drug development and drug manufacturing is required to demonstrate that the methods are fit for their intended purpose. Additionally, the pharmaceutical industry around the world is subject to extensive regulations due to the nature of its products. Analytical chemists play important roles in monitoring the drugs in their dosage forms and biological samples. From the viewpoints mentioned above, the title of this special issue was chosen so as to ask chemists to appreciate their great roles in chemistry science. This special issue features 8research articles. In this special issue, development of chromatographic methods such as high performance liquid chromatography, gas chromatography, micellar liquid chromatography, and their validations is presented. The purpose of this special issue will be to serve as a guide to what chromatographic methods bring to analytical and medicinal chemistry and other pharmaceutical sciences as well as briefly review their role in drugs and the new developments and validation of assay methods of pharmaceutically active compounds. Also, recent developments of application, evaluation, and validation of chromatographic methods are focused on by key topics in drug developments and analysis by assessment of the distinguished authors of this special issue. We hope that the reader will find a number of topics of interest and that additional new ideas will emerge from this special issue.

The electrochemical behavior and determination of nabumetone, nonsteroidal anti-inflammatory drug, were studied in aqueous alcohol medium at a glassy carbon electrode using cyclic, differential pulse (DP) and osteryoung square wave (OSW) voltammetric techniques. In pH 3.7 acetate buffer, nabumetone solution presents a well-defined anodic response at 1.2 V as shown by the proposed methods. The anodic peak was characterized as being irreversible and diffusion-controlled. The slope of the log ip - log v linear plot was 0.52 indicating the diffusion control for pH 3.7 acetate buffer solution. Under optimal conditions, a detection limit of 7.65 x 10(-8) M for DPV and 3.60 x 10(-8) M for OSW, and a linear calibration graph in the range from 1 x 10 - 6 M to 8 x 10 - 5 M were obtained for both methods. The procedure was successfully applied to the determination of the drug in tablets, spiked human serum and spiked human urine with good recoveries. The detection limits were 2.31 x 10(-7) M and 2.53 x 10(-7) M in human serum and 2.68 x 10(-7) M and 2.51 x 10(-7) M in human urine for DPV and OSWV method, respectively.

Amlodipine besylate (AML) is a long-acting calcium channel blocker used as an antihypertensive agent. Valsartan (VAL) is also used to treat hypertension, either alone or in combination with other agents. Two-component mixtures of AML and VAL were analyzed by HPLC and the ratio spectra of the first derivative spectrophotometric technique. The spectrophotometric method depends on the first derivative of the ratio-spectra by measurements of the amplitudes at 234.0 nm for VAL and 351.0 nm for AML. Calibration graphs were established for 0.520 g/mL AML and 132 g/mL VAL using the ratio spectra of the first derivative spectrophotometric method. In the HPLC method, an ACE 5 C18 (4.6 150 mm, 5 m) RP column at 30C with the mobile phase methanolacetonitrileNaH2PO4H2O buffer, including 5 mL/L triethylamine and adjusted to pH 3.0 (42 + 18 + 40, v/v/v) at 2.0 mL/min flow rate was used to separate both compounds with detection at 254.0 nm. Linearity was obtained in the concentration range of 0.5500 g/mL for AML and 5.0900 g/mL for VAL. The proposed methods have been extensively validated. These methods allow a number of cost- and time-saving benefits. They were successfully applied to the determination of AML and VAL in synthetic mixtures and in a pharmaceutical dosage form. There was no significant difference between the performance of the proposed methods regarding the mean and SD values. The proposed methods are simple, rapid, and suitable for QC applications.