ABSTRACT
A new flow-injection (FI) and high performance liquid chromatography (HPLC) with chemiluminescence detection method has been proposed for the determination of α-lipoic acid (LA). The assay is based on the measurement of chemiluminescence (CL) produced during the reaction of α-lipoic acid with potassium permanganate in a sodium hexametaphosphate medium (pH 3). This reaction is accompanied by a weak CL, which is greatly increased in the presence of a formaldehyde solution. The proposed FI method allows the determination of LA over the range: 0.5-20µgmL(-1) with LOD 4×10(-3)µgmL(-1). An introduction of HPLC into the flow manifold improves selectivity of the method and allows the determination of LA in a complex sample. The chromatographic linear range is 2.5-30µgmL(-1) with LOD 1.774µgmL(-1). Chromatographic separation was achieved by isocratic elution (acetonitrile/potassium dihydrogen phosphate, pH 3, adjusted with phosphoric acid): 30/70 using a Cosmosil 5C(18)-MS-II (4.6mm×150mm I.D.) column at a flow rate of 1.0mLmin(-1). The presented methods were utilized to determine the α-lipoic acid content in "Alfa-lipoic acid" capsules and in food products.
Subject(s)
Chromatography, High Pressure Liquid/methods , Flow Injection Analysis/methods , Luminescent Measurements/methods , Thioctic Acid/analysis , Thioctic Acid/chemistry , Food Analysis , Formaldehyde/chemistry , Oxidants/chemistry , Oxidation-Reduction , Phosphates/chemistry , Potassium Permanganate/chemistry , Thioctic Acid/isolation & purificationABSTRACT
Some amino acids were found to react with carbonyl functional groups of humic acid. Products of this reaction give strong chemiluminescence during their oxidation with N-bromosuccinimide (NBS) in alkaline solution. Humic acids from different sources produced similiar signal magnitude. This effect was employed to the flow-injection determination of glycine and arginine in pharmaceutical formulations with considerable selectivity against different amino compounds. The proposed method is fast and simple. Detection limit is 0.20 and 0.25 mg.l(-1) for glycine and arginine respectively, and 115 samples per h can be determined.
ABSTRACT
Hydrogen peroxide, potassium permanganate, potassium dichromate, potassium hexacyanoferrate(III), cerium(IV) sulphate and sodium peroxidisulphate have been tested as potential reagents for chemiluminescence generation from the oxidation of phenothiazine derivatives. Only with potassium permanganate in acidic medium were satisfying results achieved. A total of 13 different phenothiazine derivatives produce luminescence of different intensities on oxidation. Thioridazine hydrochloride was chosen to develop a rapid and simple method for its determination in pharmaceutical formulations. The limit of detection is 1.2 x 10(-6) mol l(-1), and 110 samples per hour can be determined.
Subject(s)
Antipsychotic Agents/analysis , Thioridazine/analysis , Flow Injection Analysis , Indicators and Reagents , Luminescent Measurements , Oxidants , Potassium Permanganate , TemperatureABSTRACT
A flow-injection manifold is proposed for the determination of epinephrine. The experimental procedure is based on the indirect biamperometric detection of the drug by using Fe(III)-Fe(II) as an indicating redox system and a flow-through detector with two polarized Pt wire electrodes. The calibration graph is linear over the range 0.3-20 micrograms ml-1 of epinephrine. The relative standard deviation for the determination of 10 micrograms ml-1 of epinephrine is 1.5% (n = 25) and the sample throughput is 153 h-1. The method was applied to the determination of epinephrine in two commercially available pharmaceutical preparations.
Subject(s)
Epinephrine/analysis , Flow Injection Analysis , Electrochemistry , Electrodes , Ferric Compounds , Ferrous Compounds , Oxidation-Reduction , Sensitivity and Specificity , Time FactorsABSTRACT
A method for the spectrophotometric determination of promazine by flow injection analysis is reported. The procedure is based on the reaction of promazine with molybdophosphoric acid. Concentrations of promazine in the range 1-25 ppm have been determined with a relative standard deviation of 1.8% at 10 ppm (n = 20). The method was applied to the determination of promazine in injections and compared favourably with an independent reference method based on spectrophotometry.
Subject(s)
Promazine/analysis , Calibration , Flow Injection Analysis , Indicators and Reagents , Molybdenum , Phosphoric Acids , Spectrophotometry, UltravioletABSTRACT
The determination of several N-substituted phenothiazine derivatives was carried out by the reaction of the drug with managanese dioxide entrapped in a polymeric material in a packed-bed reactor; the oxidized drug was monitored at lambda(max). The calibration graph is linear over the range 5-50 mug/ml of phenothiazine derivatives with a relative standard deviation of 0.5-1% (at 10 mug/ml) and sample throughput of 40-48 h(-1). The influence of foreign compounds was studied and the method was applied to the determination of six different phenothiazine derivatives in pharmaceutical formulations.
ABSTRACT
A simple flow-injection spectrophotometric method for the determination of promazine is described. The two proposed procedures are based on the oxidation of analyte with a manganese dioxide column. Concentrations of promazine in the ranges 2-20 and 1-6 are determined with a relative standard deviation of 1.0%. The injection rates are 62 and 80 samples h-1, respectively. The influence of foreign species and the determination of promazine in a pharmaceutical formulation are also reported.
Subject(s)
Chemistry, Pharmaceutical/methods , Flow Injection Analysis , Manganese Compounds , Oxides , Promazine/analysis , Calibration , Hydrogen-Ion Concentration , Manganese/chemistry , Oxidation-Reduction , Spectrophotometry, UltravioletABSTRACT
A single channel FIA assembly is proposed for the spectrophotometric determination of adrenaline, the aqueous sample solution is directly injected into the carrier stream leading the sample through a manganese dioxide column at 80 degrees C, and on to the spectrophotometer flow-cell. The calibration graph is linear up to 17 ppm of adrenaline. The influence of other substances has been studied and the method has been applied to the determination of adrenaline in a pharmaceutical formulation.
Subject(s)
Epinephrine/analysis , Chromatography/instrumentation , Indicators and Reagents , Oxidation-Reduction , Spectrophotometry, Ultraviolet/instrumentationABSTRACT
Optimum conditions have been established for the formation and extraction of the complex of methopromazine with platinum(IV) in hydrochloric acid and an extractive spectrophotometric method for the determination of platinum is described.
