Differential Pulse Anodic Voltammetric Determination of Chlorzoxazone in Pharmaceutical Formulation using Carbon Paste Electrode.

The electrochemical behavior of chlorzoxazone at the carbon paste electrode was investigated in 0.04 mol/L Britton-Robinson buffer pH 6.50 using cyclic and differential pulse voltammetric techniques. Cyclic voltammetric studies indicated that the oxidation of the drug was irreversible and controlled mainly by diffusion. Experimental and instrumental parameters were optimized (50 mV/s scan rate, 50 mV pulse amplitude, and 0.04 mol/L Britton-Robinson (BR) buffer pH 6.50 as a supporting electrolyte) and a sensitive differential pulse anodic voltammetric method has been developed for the determination of the drug over the concentration range 0.17-1.68 µg/mL chlorzoxazone, with detection and quantitation limits of 0.05 and 0.16 µg/mL, respectively. The proposed voltammetric method was successfully applied to the determination of the drug in its pharmaceutical formulation (Myoflex tablets), and in spiked human urine samples.

Extraction-free spectrophotometric assay of the antitussive drug pentoxyverine citrate using sulfonephthalein dyes.

Pentoxyverine citrate (PEN-citrate) is an antitussive (cough suppressant) drug used for cough associated with illnesses like common cold. In this work, PEN-citrate is quantified by applying a simple, direct and accurate spectrophotometric method in pure form, pharmaceutical formulation (Cabella®, 2.13 mg/mL) and human serum samples. The formation of a stable yellow ion-pair with sulfonephthalein dyes; bromocresol green (BCG), bromophenol blue (BPB), bromothymol blue (BTB), bromocresol purple (BCP), bromochlorophenol blue (BChPB) and bromoxylenol blue (BXB), in three nonpolar solvents (chloroform, dichloromethane, acetonitrile) is used as the basis for this method. This is the first assay method reported for the quantification of PEN-citrate using the sulfonephthaleins as coloring agents. Diverse parameters were investigated in order to optimize the calibration curve conditions. The strategy was validated with respect to linearity range, precision, accuracy, specificity, robustness and limits of detection (LOD) and quantification (LOQ). In addition, solvents of different polarities were utilized to investigate the color reaction, light absorption and to allow for increasing the method sensitivity. Beer's law is obeyed over a wide concentration range (up to 42.05 µg/mL in case of BTB method). LOD and LOQ values reached 0.22 and 0.72 µg/mL, respectively, upon using BChPB. The relative standard deviation (%RSD) was ≤1.91% while correlation coefficient values (r) were ≥ 0.9974. High molar absorptivity values and low values of Sandell's sensitivity were obtained indicating that the proposed methods are highly sensitive. The validated methods were applied to the analysis of PEN-citrate in the dosage form and human serum samples where the drug was successfully resolved from the pharmaceutical additives and serum components with recoveries ≥98.98%.

Simultaneous quantification of simeprevir sodium: A hepatitis C protease inhibitor in binary and ternary mixtures with sofosbuvir and/or ledipasvir utilizing direct and H-point standard addition strategies.

Simeprevir sodium (SMV); a novel hepatitis C inhibitor, quells hepatitis C viral replication by binding to and repressing the protease, hepatitis C infection (HCV) NS3/4A. In this way, it is known as a prompt acting antiviral agent. Calibration curves of SMV were built in various solvents; ethanol, methanol, acetonitrile, chloroform and dichloromethane. It is obeyed up to 60.0 µg/mL; in all solvents at two maximum wavelengths (280 and 327 nm). Several investigations show that, SMV might be present in a mixture of Sofosbuvir (SOF) and/or Ledipasvir (LDP). So far as that is concerned, H-point standard addition strategy (HPSAS) is made to identify it in binary or ternary mixtures. Recovery studies are in the prevalent range (93.0-107.0%) with relative standard deviation <1.5%. A correlation between the developed techniques is carried out and it demonstrates that these strategies are effectively applied for the simultaneous analysis of SMV, SOF and LDP in several synthetic samples and pharmaceutics. Statistical treatment of the acquired data is carried out against a newly published HPLC technique using F- and t-treatments.

Chemically modified carbon paste and membrane sensors for the determination of benzethonium chloride and some anionic surfactants (SLES, SDS, and LABSA): Characterization using SEM and AFM.

Chemically modified carbon-paste (CMCP) and membrane- sensors based on incorporating benzothonium-tetraphenylborate (BT-TPB) were constructed for the analysis of benzethonium chloride, and some other surfactants such as sodium lauryl ether sulphate (SLES), sodium dodecyl sulphate (SDS), and linear alkylbenzene sulphonic acid (LABSA). All sensors showed good sensitivity and reverse wide linearity over a concentration range of 5.97×10(-7) to 1.00×10(-3) and 5.96×10(-7) to 3.03×10(-3)molL(-1) with limit of detection of 3.92×10(-7)and 3.40×10(-7)molL(-1) for membrane and chemically modified carbon paste sensors, respectively, with respect to benzethonium chloride (BT.Cl). They could be used over a wide pH range of 2.0-10.0. The thermal coefficients of membrane and CMCP sensors are 5.40×10(-4), 1.17×10(-4)V/°C, respectively. The sensors indicated a wide selectivity over different inorganic cations. The effect of soaking on the surface morphology of the membrane sensor was studied using EDX-SEM and AFM techniques. The response time was <10s The freshly prepared, exhausted membrane, and CMCP sensors were successfully applied for the potentiometric determination of the pure BT.Cl solution. They were also used for the determination of its pharmaceutical formulation Dermoplast(®) antibacterial spray (20% benzocaine+0.2% benzethonium chloride) with recovery values ranging from 97.54±1.70 to 101.25±1.12 and from 96.32±2.49 to 101.23±2.15%. The second goal of these sensors is the potentiometric determination of different surfactants such as SLES, SDS, and LABSA with good recovery values using BT.Cl as a titrant in their pure forms, and in samples containing one of them (shampoo, Touri(®) dishwashing liquid, and waste water). The statistical analysis of the obtained data was studied.

Determination of residues of acetaminophen, caffeine, and drotaverine hydrochloride on swabs collected from pharmaceutical manufacturing equipment using HPLC in support of cleaning validation.

An HPLC method was developed for the simultaneous determination of residues of acetaminophen (paracetamol, PA), caffeine (CA), and drotaverine HCl (DH) on swabs collected from pharmaceutical manufacturing equipment surfaces. The challenge in cleaning validation is to develop analytical methods that are sensitive enough to detect traces of the active compounds remaining on the surface of pharmaceutical manufacturing equipment after cleaning. Chromatography was performed in the isocratic mode on a Hypersil C18 BDS column using the mobile phase 0.02 M tetrabutylammonium bisulfate-methanol (100 + 45, v/v) at 50°C with UV detection at 210 nm. The method was tested for specificity, linearity, LOD, LOQ, accuracy, and precision for determination of traces of the above-mentioned drugs. The time required for a single analysis was 12 min. The response was linear in the ranges of 6.900-52.100, 1.040-7.800, and 0.694-5.210 µg/mL for PA, CA, and DH, respectively.

Charge-transfer complexes of pyrimidine Schiff bases with aromatic nitro compounds.

Charge-transfer (CT) complexes of pyrimidine Schiff bases, derived from condensation of 2-aminopyrimidine and substituted benzaldehydes, with some aromatic polynitro compounds were prepared and investigated using IR, UV, visible and (1)H NMR spectroscopy. For all solid complexes, the main interaction between the donor and acceptor molecules takes place through the π-π* interaction. Strong and some weak acidic acceptors, in addition interact through proton transfer from the acceptor molecule to the basic centre of the electron donor. Also, an n-π* transition was detected in some complexes.

Construction and performance characterization of ion-selective electrodes for potentiometric determination of pseudoephedrine hydrochloride applying batch and flow injection analysis techniques.

New pseudoephedrine selective electrodes have been constructed of the conventional polymer membrane type by incorporation of pseudoephedrine-phosphotungstate (PE-PT) or pseudoephedrine-silicotungstate (PE-SiT) ion-associates in a poly vinyl chloride (PVC) membrane plasticized with dibutyl phthalate (DBP). The electrodes were fully characterized in terms of the membrane composition, temperature, and pH. The electrodes exhibited mean slopes of calibration graphs of 57.09 and 56.10 mV concentration decade(-1) of PECl at 25 degrees C for (PE-PT) and (PE-SiT) electrodes, respectively. The electrodes showed fast, stable, and near-Nernstian response over the concentration ranges 6.31 x 10(-6)-1.00 x 10(-2) and 5.00 x 10(-5)-1.00x10(-2) M in the case of PE-PT applying batch and flow injection (FI) analysis, respectively, and 1.00 x 10(-5)-1.00 x 10(-2) and 5.00 x 10(-5)-1.00x10(-2) M in the case of PE-SiT for batch and FI analysis system, respectively. Detection limit was 5.01x 10(-6) M for PE-PT electrode and 6.31x10(-6) M for PE-SiT electrode. The electrodes were successfully applied for the potentiometric determination of pseudoephedrine hydrochloride (PECl) in pharmaceutical preparations with mean recovery 101.13 +/- 0.85% and 100.77+0.79% in case of PE-PT applying batch and flow injection systems, respectively, and 100.75+0.85% and 100.79 +/- 0.77% in case of PE-SiT for batch and flow injection systems, respectively. The electrodes exhibited good selectivity for PECl with respect to a large number of inorganic cations, sugars and amino acids.

Ion-selective electrodes for potentiometric determination of ranitidine hydrochloride, applying batch and flow injection analysis techniques.

New ranitidine hydrochloride (RaCl)-selective electrodes of the conventional polymer membrane type are described. They are based on incorporation of ranitidine-tetraphenylborate (Ra-TPB) ion-pair or ranitidine-phosphotungstate (RaPT) ion-associate in a poly(vinyl chloride) (PVC) membrane plasticized with dioctylphthalate (DOP) or dibutylphthalate (DBP). The electrodes are fully characterized in terms of the membrane composition, solution temperature, and pH. The sensors showed fast and stable responses. Nernstian response was found over the concentration range of 2.0 x 10(-5) M to 1.0 x 10(-2) M and 1.0 x 10(-5) M to 1.0 x 10(-2) M in the case of Ra-TPB electrode and over the range of 1.03 x 10(-5) M to 1.00 x 10(-2) M and 1.0 x 10(-5) M to 1.0 x 10(-2) M in the case of Ra-PT electrode for batch and FIA systems, respectively. The electrodes exhibit good selectivity for RaCl with respect to a large number of common ions, sugars, amino acids, and components other than ranitidine hydrochloride of the investigated mixed drugs. The electrodes have been applied to the potentiometric determination of RaCl in pure solutions and in pharmaceutical preparations under batch and flow injection conditions with a lower detection limit of 1.26 x 10(-5) M and 5.62 x 10(-6) M at 25 +/- 1 degrees C. An average recovery of 100.91% and 100.42% with a relative standard deviation of 0.72% and 0.53% has been achieved.

PVC membrane ion-selective electrodes for the determination of Hyoscyamine in pure solution and in pharmaceutical preparations under batch and flow modes.

New PVC membrane electrodes selective for the determination of hyoscyamine ion (Hy(+)) based on hyoscyamine tetraphenylborate (Hy-TPB) or hyoscyamine phosphotungstate (Hy-PT) ion-exchangers as electroactive materials are described. The electrodes show a linear response for Hy(+) over the concentration range of 1.00 x 10(-5) to 1.26 x 10(-2) mol L(-1) and 1.00 x 10(-4) to 1.00 x 10(-2) mol L(-1) in case of Hy-TPB electrode applying batch and flow injection analysis (FIA), respectively, and 1.00 x 10(-5) to 4.52 x 10(-3) mol L(-1) and 6.31 x 10(-5) to 1.00 x 10(-2) mol L(-1) in case of Hy-PT electrode for batch and FIA, respectively. The lower detection limits are 3.90 x 10(-6) and 4.51 x 10(-6) at 25 degrees C for Hy-TPB and Hy-PT electrodes, respectively. The electrodes posses near Nernstian slopes of 56.5 and 57.8 mV/decade for Hy-TPB and Hy-PT electrodes, respectively, and a fast potential response of < or =20 s which is almost constant over a pH range of 3-10. Selectivity coefficient data for some common inorganic cations, sugars, amino acids and the components, other than hyoscyamine, of the mixed drugs investigated show negligible interference. The electrodes have been applied to the potentiometric determination of hyoscyamine in pure solution and in pharmaceutical preparations under batch and FIA conditions and as end point indicator electrode for the determination of hyoscyanine using potentiometric titration. For the concentrations (1.08 x 10(-5) mol L(-1) to 3.16 x 10(-3) mol L(-1)) an average recovery of 99.95% with relative standard deviation of 0.63% has been achieved. The effect of temperature on the electrodes was also studied.

Conductimetric determination of phenylpropanolamine HCl, ranitidine HCl, hyoscyamine HBr and betaine HCl in their pure state and pharmaceutical preparations.

Sodium tetraphenylborate and phosphotungstic acid were used as titrants for the conductimetric determination of phenylpropanolamine HCl (PPA.Cl), ranitidine HCl (Ra.Cl), hyoscyamine HBr (Hy.Br) and betaine HCl (Be.Cl) through ion-associate complex formation. The molar combining ratio and the solubility products of the formed ion-associates were studied and calculated. The suggested method has been applied to the determination of the mentioned drugs in their pure state and pharmaceutical preparations with mean recovery values of 97.71-102.97% and relative standard deviations 0.25-0.85%. The accuracy of the method is indicated by excellent recovery and low standard deviation. The results are compared with the pharmacopoeial or the official methods.

Potentiometric flow injection analysis of mebeverine hydrochloride in serum and urine.

Four PVC membrane electrodes for the determination of mebeverine hydrochloride (MvCl) were fabricated and fully characterized in terms of composition, life span, usable pH range, working concentration range and temperature. The membranes of these electrodes consist of mebeverinium-silicotungstate (Mv-ST), silicomolybdate (Mv-SM), phosphotungstate (Mv-PT), or phosphomolybdate (Mv-PM) ion-associations dispersed in PVC matrix with dibutyl phthalate plasticizer. The electrodes showed near-Nernstian response over the concentration range of 4.0 x 10(-6) to 1.0 x 10(-2)M MvCl and were applied to the potentiometric determination of mebeverinium ion in pharmaceutical preparations, serum and urine in steady state and flow injection (FI) conditions with average recoveries of 96.4-102 % and relative standard deviations of 0.132-1.86%. The electrodes exhibit good selectivity for MvCl with respect to a large number of inorganic cations, organic cations, sugars and amino acids. The sensitivities of these electrodes are high enough to measure as low as 1.86 microg/ml of MvCl which permit the determination of the Ksp values of the ion-associates used. The proposed potentiometric methods offer the advantages of simplicity, accuracy, automation feasibility and applicability to turbid and colored sample solutions.

Conductometric and indirect AAS determination of antimalarials.

Two methods are described for the determination of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate, based on the formation of their ion-associates with [Cd(2+), Co(2+), Mn(2+) and Zn(2+)] thiocyanate, ammonium reineckate and/or sodium cobaltinitrite. The molar combining ratio reveal that (1:1) (drug:reagent) ion associates are formed for all reagents except for ammonium reineckate which form (1:2) ion associates with all studied drugs. The optimum conditions for the ion-association have been studied. Conductometric method was applied for the direct determination of the suggested drugs in bulk powders, whereas indirect atomic absorption spectrometric method, depending on the measurement of the excess metal ion present in supernatant solutions after precipitation of the ion associates is used to calculate the drug concentration. Optimum concentration ranges for the determination of aminoquinoline antimalarial drugs under consideration were 0.46-12.90 and 0.155-3.87 mg using conductometric and indirect atomic absorption spectral methods, respectively. The proposed procedures have been applied successfully to the analysis of these drugs in certain formulations and the results are favourably comparable to the official methods.