Indirect Kinetic–Spectrophotometric Determination of Resorcinol, Catechol, and Hydroquinone

A rapid, simple, and sensitive method for the determination of trace amounts of resorcinol, catechol, and hydroquinone in aqueous media has been proposed. The method is based on their reaction with nitrite. The excess nitrite is then determined by a kinetic method based on its reaction with Neutral Red. The reaction is monitored spectrophotometrically by measuring the decrease in the absorbance at 530 nm by a fixed time method. Resorcinol, catechol, and hydroquinone could be determined by the proposed method in the ranges of 0.1–2.0 mg/mL, 0.25–2.0 mg/mL and 0.1–3.0 mg/mL, respectively. The method was applied to the determination of resorcinol and catechol in pharmaceutical formulations with satisfactory results.     

Simultaneous Determination of Cephradine,L‐Arginine,and Cephalexin in Cephradine for Injection by Capillary Zone Electrophoresis

Abstract

Applying capillary zone electrophoresis (CZE) to separate the components of Cephradine for Injection: cephradine, and L‐arginine, as well as cephalexin, which is the degradation product of cephradine was studied. The best results were achieved with background electrolyte consisting of 50 mM disodium hydrogen phosphate buffer at pH 6.5 and an applied voltage of 20 kV in a bare fused‐silica capillary. The samples were injected at 50 mbar for 4 s. The capillary temperature was 25°C and the UV detection was performed at a wavelength of 195 nm. Histidine was used as internal standard (IS) to ensure acceptable precision data. The linear ranges of cephradine, L‐arginine, and cephalexin were 93.8–6255.6 µg/mL, 47.9–3195.2 µg/mL, and 6.1–405.4 µg/mL, respectively. Quantitative parameters such as accuracy, precision, limit of detection (LOD), and limit of quantitation(LOQ) were all established in CZE mode.     

Simultaneous Determination of Phenolic Compounds in Red Wines by HPLC‐UV

Abstract

Ten samples of commercially Italian red wines were analyzed in order to determine the phenolic content. Variations in wine types are largely due to differences in concentration and composition of these compounds. Polyphenolic compounds are a large and complex group of substances which constitute one of the most important quality parameters of wine. These constituents of red wine contribute to organoleptic characteristics and to antioxidant and anti‐inflammatory properties. Moderate wine consumption is associated with several beneficial physiological effects, which include anticancer activities, inhibition of platelet aggregation, and inhibition of LDL oxidation which constitutes the initial stage of the pathogenesis of arteriosclerosis.

For the analysis, reversed‐phase high performance liquid chromatography (HPLC) method coupled with UV‐Vis detection was used. The method uses a gradient elution to identify nine biologically active phenolic constituents: catechin; epicatechin; trans‐ and cis‐resveratrol; gallic, chlorogenic and caffeic acid; rutin and quercetin in red wine samples. The samples are injected directly without any pretreatment. The method is simple, fast, not expensive and shows good linearity for all constituents, and the detection limits ranged from 0.3–1.6 µg/ml for trans‐resveratrol and gallic acid, respectively. Moreover, the samples were analyzed in different times for estimation of stability of these compounds.     

Simultaneous Determination of Magnolol and Honokiol by Synchronous Fluorescence Spectroscopy

MOL and HOL are the useful ingredients of Houpo that has been used in traditional Chinese medicine for the treatment of thrombotic stroke, typhoid fever, and headache. Therefore, it is necessary to determine theirs contents in pharmaceutical dosage. Up to…     

Simultaneous Determination of Levomepromazine Hydrochloride and Its Sulfoxide by UV‐Derivative Spectrophotometry and Bivariate Calibration Method

Abstract

Two spectrophotometric methods are proposed for the simultaneous quantification of levomepromazine hydrochloride (LV) and its main degradation product levomepromazine sulfoxide (LV‐SO). One of them is based on the first order derivative spectra generated by the Savitzky‐Golay algorithm (third‐order polynomial degree, Δλ=10 nm). Determination of levomepromazine hydrochloride and its sulfoxide was realized by measurements of amplitudes of derivative spectra at 332 nm and 278 nm, respectively. The Beer law was obeyed in the concentration range 1.5–50 µg/mL for LV and 2.5–50 µg/mL for LV‐SO. The second of the proposed methods utilized the bivariate calibration algorithm. The determination was performed at 302 nm for levomepromazine and at 334 nm for sulfoxide. The elaborated methods allowed determination of LV in the concentration range 1.0–25 µg/mL while LV‐SO was determined in the concentration range 2.0–50 µg/mL.     

Simultaneous Determination of Samarium and Gadolinium by a Automated Stopped-flow Analyzer

The present paper contains the reaction mechanism of the rare earth complex with 2-(2-arsenophenylazo)-7-(2, 6-dichloro-4-fluoro-phenylazo)- 1, 8-dihydroxynaphthalene-3, 6-disulfonic acid (DCF-arsenazo) studied preliminarily with a fully automated stopped-flow analyzer. A method with a high sensitivity and selectivity is proposed for the simultaneous determination of samarium and gadolinium based on the differential kinetic reaction of the rare earth complex with DCF-arsenazo. Sm and Gd in their concentrated oxides were determined with the relative errors less than 6%.     

Simultaneous Determination of Methadone,Heroin, Cocaine and their Metabolites in Urine by GC‐MS

Abstract

A gas chromatographic‐mass spectrometric (GC‐MS) method for the determination of methadone, heroin, cocaine, and their metabolites in urine using Selected Ion Monitoring (SIM) was developed. Following a liquid‐liquid extraction with Toxitubes A^® and using their deuterated analogs as internal standards, the analytes were derivatized with 99:1 (v/v) N,O‐bis‐trimethylsilyl‐trifluoroacetamide/trimethylchlorosilane and injected by hand, in the splitless mode, at 240°C and a purging time of 0.75 min. The mass selective detector was kept at 300°C and molecules were ionized in the electron impact mode, using an energy of 70 eV. The detector response was linear for all drugs studied over the range 50–1000 ng/mL.     

Indirect Determination of CTMAB with Sodium Chloride and Ammonium Thiocyanate by Floatation and Separation of Zinc

Cetyl-trimethylammoniumbromide(CTMAB)isaveryusefulcationicsurfactant,sothestudyondeterminationofCTMABassumesgreatimportance.AsmallamountofCTMABisgenerallydeterminedbyspectrophotometrybasingCTMABcombineswithtriazidetoformcoloredbinaryion-associationcomplex1-3.However,thosemethodsofdeterminationofCTMABhavedisadvantagesofsmalllinearrange,needofspecialreagent,determinationinbaseenvironment,etc.Inthispaper,indirectdeterminationofCTMABwithNaClandNH4SCNbyfloatationandseparationofZn(II…     

Simultaneous Determination of 13 Phenoxy Acid Herbicide Residues in Soybean by GC‐ECD

Abstract

In this study, a gas chromatography method for the multiresidue determination of 13 phenoxy acid herbicide residues (4‐CPA, 4‐CPP, phenoxy butyric acid, dicamba, MCPA, MCPP, MCPB, 2,4‐D, 3,4‐D, 2,4,5‐T, 2,4,5‐TP, 2,4‐DP, and 2,4‐DB) in soybean was developed. After the removal of fat using n‐hexane, the sample was extracted with acetonitrile‐50 mM HCl (v/v 7:3), and then followed by liquid‐liquid partition with n‐hexane (saturated by acetonitrile). The soybean extract was further cleaned up by anion exchange column. Then the residues were derived with pentafluorobenzyl bromide and the resulting pentafluorobenzyl (PFB) esters were analyzed by a gas chromatograph equipped with an electron capture detector (ECD), quantified by the external standard method. Recoveries of spiked samples at two fortified levels (0.01 and 0.1 mg/kg) are all above 70%. And the relative standard deviation was less than 20%. It shows that the limits of determination (LOD) of this method (S/N≥3) can meet the requirement of maximum residue analysis in import/export inspection for soybean.     

Indirect Determination of Ascorbic Acid with Ammonium Sulfate and Isopropyl Alcohol by Extraction-flotation of Copper

A new method of indirect determination of ascorbic acid(Vc) with ammonium sulfateand isopropyl alcohol by extraction-flotation of copper is studied in this paper. It shows that asmall amount of Cu( II ) can be reduced to Cu( I ) by Vc, then Cu( I ) reacted with the SCN-,which precipitated on the interface of isopropyl alcohol and H2O. A good linear relationshin is observed between the flotation yield(E) of Cu( II ) and the amount of Vc. The detection limi(forVc is 1.76 μg/mL. The method is simple, rapid (5 rain), but suffers from little interference of common anions and cations. It has been successfully applied for the determination of Vc in fruits.     

The Simultaneous Determination of Cu Ph Cd and Sb by Derivative Adsorption Chronopotentiometry

Anodic stripping voltammetry (ASV) is an effective electroanalytical technique for themeasurement of trace metal ions. But there are serious interferences due to overlappingstripping peaks and forming of intermetallic complex in complicated system. The peak ofcopper (ASV) is close to that of mercury. So the result of determination of copper is notsatisfactory. Adsorption chronopotentiometry was reported by H.Eskilsson et al i. In thismethod, instead of electrolytic accumulation of metal io…     

Simultaneous Determination of Fluvoxamine and Its Metabolites in Human Liver Microsomes by High‐Performance Liquid Chromatography with Solid‐Phase Extraction

Abstract

A simple and sensitive high‐performance liquid chromatography method was developed for the simultaneous quantitative determination of fluvoxamine and its two metabolites, fluvoxamino alcohol and fluvoxamino acid, in human liver microsomes. Chromatographic separation was achieved with a Grand‐pak C4‐5 column using a mobile phase at pH 2.5 of 0.5% KH₂PO₄‐acetonitrile (75:25, v/v). Analysis involved a solid‐phase extraction with an Oasis HLB cartridge, which gave high extraction recovery (>92.8%) with good selectivity. The lower limit of quantification of this assay was 78.6 nM for fluvoxamine and fluvoxamino acid, and 82.2 nM for fluvoxamino alcohol, respectively. The coefficient of variation of intra‐ and interday assays was less than 5.8% and accuracy was within 5.3% for all analytes (concentration range 78.6 nM–2.36 µM for fluvoxamine and fluvoxamino acid, and 82.2 nM–2.47 µM for fluvoxamino alcohol, respectively). This method is applicable for accurate and simultaneous determination of oxidative metabolites of fluvoxamine by human liver microsomes.     

Kinetic Study of Radical Polymerization v. Determination of Reactivity Ratio in Copolymerization of Acrylonitrile and Itaconic Acid by 1H‐NMR

Many reports exist in the literature about the application of ¹H and ¹³C‐NMR techniques to analyze the copolymer structure and composition and also determination of reactivity ratios. In this work, on‐line ¹H‐NMR spectroscopy has been applied to identify reactivity ratios of itaconic acid and acrylonitrile in the solution phase (DMSO as the solvent) and in the presence of AIBN as the radical initiator. All the peaks corresponding to the existing protons were assigned quietly. Therefore, the kinetics of the copolymerization reaction was investigated by studying the variation of integral of two characteristic peaks regarding each monomer. The obtained data were used to find the reactivity ratios of acrylonitrile and itaconic acid by linear least‐squares methods such as Finemann‐Ross, inverted Finemann‐Ross, Mayo‐Lewis, Kelen‐Tudos, extended Kelen‐Tudos and Mao‐Huglin. In addition, a non‐linear least‐square method (Tidwell‐ Mortimer) was used at low conversions. Extended Kelen‐ Tudos and Mao‐Huglin were applied to determine reactivity ratio values at high conversions as well.     

Simultaneous Determination of Gold and Platinum by Double Artificial Neural Network Analysis with Flow-injection

A highly sensitive double artificial neural network （DANN） analysis with flow-injection chemiluminescence （FI-CL） has been developed to simultaneously determine the trace amounts of the gold and platinum in simulated mixed samples, without the boring process.     

Kinetic Potentiometric Determination of some Thiols with Iodide Ion‐Sensitive Electrode

Abstract

This paper describes a kinetic potentiometric method for the determination of thiols (RSH): l‐cysteine (cys), N‐acetyl‐l‐cysteine (NAC), l‐glutathione (glu), and d‐penicillamine (pen). The proposed method is based on the reaction of formation the sparingly soluble salts, RSAg, between RSH and Ag⁺ ions. During this reaction potential‐time curves were recorded by using an electrochemical cell with commercial iodide selective electrode. The rectilinear calibration graphs are obtained in the RSH concentration range from 1.0×10^?5 to 1.0×10^?3 M. The applicability of the proposed method was demonstrated by determination of chosen compounds in pharmaceutical dosage forms.     

New Validated Methods for the Simultaneous Determination of Two Multicomponent Mixtures Containing Guaiphenesin in Syrup by HPLC and Chemometrics‐Assisted UV‐Spectroscopy

Abstract

High pressure liquid chromatographic (HPLC) and spectrophotometric methods are developed for the determination of two multicomponent mixtures containing guaiphenesin, dextromethorphane hydrobromide, and sodium benzoate together with either phenylephrine hydrochloride, chlorpheniramine maleate, and butylparaben (mixture 1) or ephedrine hydrochloride and diphenhydramine hydrochloride (mixture 2). The HPLC method depended on using an ODS column with mobile phase consisting of acetonitrile ?10 mM potassium dihydrogen phosphate, pH 2.7 (40∶60 v/v) containing 5 mM heptane sulfonic acid sodium salt (for mix 1) and a cyanopropyl column with mobile phase consisting of acetonitrile ?12 mM ammonium acetate, pH 5 (40∶60 v/v) (for mix 2) and UV detection at 214 nm. The cyanopropyl column is much less hydrophobic, less sterically restricted to the penetration of bulky solute molecules into the stationary phase, and has weaker hydrogen‐bond acidity than the ODS column. So the cyanopropyl column is more suitable for separation of components of mix 2. The chemometric‐assisted spectrophotometric method with, principal component regression (PCR) and partial least squares (PLS‐1) was used. For the chemometric method a calibration set of the mixture consisting of each compound in each mixture was prepared in distilled water. The absorbance data in the UV spectra were measured in the spectral region (210–240 or 210–224 nm for mix 1 and mix 2, respectively, as this range provided the greatest amount of information about the two mixture components). The spectrophotometric method does not require a separation step. The proposed methods were successfully applied for the analysis of the two multicomponents combinations in laboratory‐prepared mixtures and in commercial syrups, and the results were compared with each other.     

Indirect Differential Pulse Voltammetric Determination of Aluminum by a Pyrocatechol Violet-Modified Electrode

Aluminumhasbeenconsideredtobeacausativeagentforvariousneurologicaldisorders'.Duringthelastdecade,considerableattentionhasbeenpaidtotheelectrochemicaldeterminationofAlforitsdistinguishedmeritsofhighsensitivity,easymanipulationandsimpleinstrumentation...     

Kinetic Study of Radical Polymerization VI. Copolymer Composition and Kinetic Parameters for Coplymerization of Styrene‐Itaconic Acid by On‐Line 1H‐NMR

Free radical solution copolymerization of styrene (St) and itaconic acid (IA) in dimethylsulfoxide‐d₆ (DMSO‐d₆) as the solvent and the use of 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at 78°C was investigated by an on‐line ¹H‐NMR spectroscopy technique. Individual monomer conversion vs. reaction time, which was calculated from the ¹H‐NMR spectra data, was used to study the drift in monomer mixture composition vs. conversion. It was found that in general, both monomers were incorporated almost equally into the copolymer. However, when the mole fraction of IA was low, the tendency of IA toward incorporation into the copolymer chain was somewhat higher than St and by increasing the mole fraction of IA in the reaction mixture, the inverse tendency was observed. Overall monomer conversion as a function of time was calculated from individual monomer conversion data and used for the estimation of k_p /k_t ^0.5 for various monomer mixture compositions. This ratio was decreased with increasing the amount of IA in the initial feed, indicating a decrease in the rate of copolymerization. Changes in the copolymer composition vs. overall monomer conversion were investigated experimentally from the NMR spectra. This was in good agreement with the changes in monomer mixture composition vs. reaction progress. Plotting the copolymer composition vs. initial monomer feed showed tendency of the system toward alternating copolymerization.     

Electrochemical and Electrocatalytic Properties of Ferrocene Incorporated in L‐Cysteine Self‐Assembled Monolayers on a Gold Electrode

Abstract

The preparation of a gold electrode modified by aminylferrocene (FcAI) covalently bound to L‐cysteine self‐assembled monolayer (L‐Cys/Au SAM) was described, and characterized by cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). In pH 7.4 buffers, FcAI incorporated in L‐Cys/Au SAM gave a pair of well‐defined and quasi‐reversible cyclic voltammetric peaks at 0.109 vs. saturated calomel eletrode (SCE), characteristic of Fe(II)/Fe(III) redox couples of the Fc. The apparent surface electron transfer rate constant is 6.86 s^?1 at the modified electrode. The immobilized Fc gave an excellent electrocatalytic activity for the oxidation of epinephrine (EP). The catalytic current of EP vs. its concentration has a good linear relation in the range of 1.7×10^?7–1.0×10^?4 mol/L, with the correlation coefficient of 0.9975 and detection limit of 1.8×10^?8 mol/L. The modified electrode can be used for the determination of EP in practical injection. The method is simple, quick, sensitive, and accurate.     

Simultaneous Determination of Mepyramine Maleate,Lidocaine Hydrochloride,and Dexpanthenol in Pharmaceutical Preparations by Partial Least‐Squares Multivariate Calibration

Abstract

A partial least‐squares calibration (PLS) method has been developed for simultaneous quantitative determination of mepyramine maleate (MAM), lidocaine hydrochloride (LIH), and dexpanthenol (DPA) in pharmaceutical preparations. The resolution of these mixtures has been accomplished by using partial least‐squares (PLS‐2) regression analysis of electronic absorption spectral data without prior separation or derivatization. The experimental calibration matrix was constructed with 27 samples. The concentration ranges considered were 2, 3, 4 µg mL^?1 for MAM, 2, 3, 4 µg mL^?1 for LIH, and 8, 10, 12 µg mL^?1 for DPA. The absorbances were recorded between 190 and 340 nm every 5 nm. The results show that PLS‐2 is a simple, rapid, and accurate method applied to the determination of these compounds in pharmaceuticals.