A novel amperometric sensor for the detection of difenidol hydrochloride based on the modification of Ru(bpy)3 on a glassy carbon electrode

An amperometric sensor for the detection of difenidol, a tertiary amine-containing analyte, was proposed. Ruthenium(II) tris(bipyridine)/multi-walled carbon nanotubes/Nafion composite film was suggested to modify the glassy carbon electrode. The modified electrode was shown to be an excellent amperometric sensor for the detection of difenidol hydrochloride. The linear range is from 1.0 × 10⁻⁶ to 3.3 × 10⁻⁵ M with a correlation coefficient of 0.998. The limit of detection was 5 × 10⁻⁷ M, which was obtained through experimental determination based on a signal-to-noise ratio of three. The sensor was employed to the determination of the active ingredients in the tablets containing difenidol hydrochloride.     

Chemiluminescence assay of promethazine hydrochloride using acidic permanganate employing flow injection mode operated with syringe and peristaltic pumps

For the first time, promethazine hydrochloride chemiluminescence emission was monitored. The paper describes a new, specific and highly sensitive flow injection (FI) method for the determination of promethazine hydrochloride using both a peristaltic and a syringe pump. The method was based on the chemiluminescence emission intensity produced as a result of its oxidation reaction with permanganate in sulfuric acid medium. Reaction variables were thoroughly investigated employing chemometrical methods with few number of experiments. The optimum system and chemical conditions were 2.1519×10⁻⁴ mol l⁻¹ permanganate in 0.01 mol l⁻¹ sulfuric acid when operating the peristaltic pump at a flow rate of 45 μl s⁻¹ and injecting the drug by a syringe pump operated at a speed of 40 μl s⁻¹. The method was found to be applicable in the concentration range of promethazine hydrochloride between 1.558×10⁻⁵ and 1.8697×10⁻³ mol l⁻¹ with a linear calibration plot of 0.992 correlation coefficient and the following equation: I=92.74+0.08048C. The method adopted proved to be highly suitable for the assay of promethazine hydrochloride in drug formulations without fear of interferences in dosage form.     

Enantiomeric Resolution on L—Carnitine Selective Polymers Prepared by Molecular Imprinting

L-carnitine selective polymers were prepared by molecular imprinting using methacrylic acid as the functional monomer. The acid function of the monomer is expected to form hydrogen bond and ionic interactions with the amine function of the target molecule L-carnitine.The imprinted polymers were used as stationary phases in high-performance liquid chromatography (HPLC). It was shown that L-carnitine imprinted polymer exhibited a higher affinity to its template molecule,while the non-imprinted polymer had no affinity to the compounds tested. Racemic carnitine hydrochloride was efficiently resolved on the L-carnitine imprinted polymer, and the separation factor is 1.9.     

A concise synthesis of (3S,4S,5R)-1-(α-d-galactopyranosyl)-3-tetracosanoylamino-4,5-decanediol, a C-glycoside analogue of immunomodulating α-galactosylceramide OCH

A concise and convergent synthesis of the C-glycoside analogue 2b of immunomodulating α-galactosylceramide OCH 1b starting from readily available 2,3,4,6-tetra-O-benzyl-d-galactose 3 and l-arabinose 6 is described. The synthesis features the nucleophilic addition of an α-ethynyl sugar 5 to the phytosphingosine-precursor aldehyde 9 and would be applicable to a variety of C-glycoside analogues of interest.     

Dynamic deswelling studies of poly(N-vinyl-2-pyrrolidone/itaconic acid) hydrogels swollen in water and terbinafine hydrochloride solutions

Deswelling kinetics of water and terbinafine hydrochloride adsorbed poly(N-vinyl-2-pyrrolidone/itaconic acid) P(VP/IA) hydrogels were investigated. Hydrogels were prepared by irradiating the ternary mixture of VP/IA and cross-linking agent ethylene glycol dimethacrylate (EGDMA) in water by γ-rays at ambient temperature. Hydrogels swelled in pure water and terbinafine hydrochloride (TER-HCl) solutions at room temperature and deswelling or water loss were investigated between 4 and 45 °C temperature range and on human skin. The influence of IA content, % swelling, temperature and TER-HCl content on the water loss from gel matrix were investigated. Induction time for 80% water loss from hydrogel systems are found to increase from 9.6 to 21.2 h by increasing IA content in the gel system at 25 °C and decreased by 11 h with addition of TER-HCl in the gel system. Kinetic analyses had shown that the basic properties affecting the water loss behavior of these hydrogels are the IA and TER-HCl content and temperature of the medium.     

Quantitation of Diltiazem Hydrochloride in Commercial Dosage Forms by Visible Spectrophotometry

A selective and sensitive visible spectrophotometric method has been described for the quantitation of diltiazem hydrochloride in commercial dosage forms. The method is based on the reaction of the tertiary amino group of the drug with sodium hypochlorite to form the chloro drug derivative, followed by the destruction of the excess hypochlorite by sodium nitrite and the subsequent development of blue color takes place by the reaction of chloro derivative of drug with starch and potassium iodide in sodium bicarbonate medium. The maximum absorbance of the resulting blue solution is read at 540 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 2.5–25.0 μg mL^?1 with a linear regression equation of A = 9.85 × 10^?4 + 4.90 × 10^?2 C and coefficient of correlation, r = 0.9999. The molar absorptivity is found to be 2.26 × 10⁴L mol^?1 cm^?1. The limits of detection and quantitation of the proposed method are 0.12 and 0.37 μg mL^?1, respectively. The proposed method has been successfully applied for the quantitation of diltiazem hydrochloride in commercial dosage forms. The results of the proposed method compared with those of Abdellatef's spectrophotometric method presented good mean recovery with acceptable true bias of all pharmaceutical samples within ± 2.0%.     

Sequential injection chromatographic determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations

A new separation method based on a novel reversed-phase sequential injection chromatography (SIC) technique was used for simultaneous determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations in this contribution.The coupling of short monolith with SIA system results in an implementation of separation step to until no-separation low-pressure method.A Chromolith^® Flash RP-18e, 25-4.6 mm column (Merck, Germany) and a FIAlab^® 3000 system (USA) with a six-port selection valve and 5 ml syringe were used for sequential injection chromatographic separations in our study. The mobile phase used was acetonitrile-water (20:90, v/v), pH 2.5 adjusted with 98% phosphoric acid, flow rate 0.48 ml min⁻¹, UV detection was at 213 nm.The validation parameters have shown good results: linearity of determination for both compounds including internal standard (ethylparaben) >0.999; repeatability of determination (R.S.D.) in the range 0.5-5.4% at three different concentration levels, detection limits in the range 0.5-2.0 μg ml⁻¹, and recovery from the pharmaceutical preparation in the range 99.3-99.9%. The chromatographic resolution between peak compounds was >5.0 and analysis time was <9 min under the optimal conditions. The method was found to be applicable for routine analysis of the active compounds ambroxol hydrochloride and doxycycline in various pharmaceutical preparations.     

12-钨磷酸共振瑞利散射光谱法测定盐酸苯海拉明

在pH值为0～1.5范围内,12-钨磷酸与盐酸苯海拉明(DP.HCl)反应形成缔合物后引起共振瑞利散射(RRS)强度显著增强,最大散射峰位于305nm,散射强度与DP.HCl浓度在8.0×10-9～1.6×10-6g/mL范围内成线性关系,据此建立了测定盐酸苯海拉明的RRS法。本法具有较高的灵敏度和良好的选择性,其检出限(3σ)为0.8×10-9g/mL。用于尿样中盐酸苯海拉明的测定,回收率为96.0%～104.2%。结合量子化学AM1法计算结果讨论了反应机理。     

A Rapid Stability-Indicating LC Method for Ziprasidone Hydrochloride

A simple and rapid reversed-phase liquid chromatographic method was developed for the related substances determination and quantitative evaluation of ziprasidone hydrochloride, which is used as an antipsychotic agent. Forced degradation studies were performed on bulk sample of ziprasidone hydrochloride using acid, base, oxidative hydrolysis, thermal stress and photolytic degradation. Mild degradation of the drug substance was observed during thermal stress and considerable degradation observed during base hydrolysis. The chromatographic method was fine tuned using the samples generated from forced degradation studies. Good resolution between the peaks corresponds to synthetic impurities and degradation products from the analyte were achieved on YMC Pack Pro C18 column using the mobile phase consists of a mixture of 0.05% v/v of phosphoric acid in water and acetonitrile. The stressed test solutions were assayed against the qualified working standard of ziprasidone hydrochloride and the mass balance in each case was close to 99.7% indicating that the developed method was stability-indicating. Validation of the developed method was carried out as per ICH requirements.     

Thermodynamic properties of some N-alkyl-N-methylpiperidinium chlorides and N-alkylpiperidine hydrochlorides in water

Densities and heat capacities at 25°C were measured for N-octyl-, N-decyl- and N-dodecyl-N-methylpiperidinium chlorides and for N-octyl- and N-dodecylpiperidine hydrochlorides in water as functions of concentration. Enthalpies of dilution at 25°C and osmotic coefficients at 37°C of the N-methyl-N-alkylpiperidinium chlorides were also measured as functions of concentration. The partial molar volumes, heat capacities, relative enthalpies, nonideal Gibbs energies and entropies at 25°C were derived as functions of the surfactant concentration. By increasing the alkyl chain length of the surfactant, both the apparent molar volume vs. concentration curves are shifted toward greater values while the corresponding ones for the heat capacity are moved toward more negative values. These results are consistent with the higher hydrophobicity the longer the alkyl chain of the surfactant is. In the micellar region, the entropy and enthalpy vs. log m/m _cmc curves increase in a parallel manner by decreasing the alkyl chain length of the surfactant. Consequently, the negligible effect of the hydrophobicity of the surfactant on the Gibbs energy vs. log m/m _cmc trends is due to the enthalpy-entropy compensative effect. The thermodynamic functions of micellization were graphically evaluated on the basis of the pseudo-phase transition model. The absolute values of both the volume and heat capacity of micellization increase with an increasing number of carbon atoms in the alkyl chain (n _c ). The enthalpy and entropy of micellization vs. n _c are convex curves. Comparisons are also made between the present data and those of some alkylpyridinium chlorides reported elsewhere.