Photochemically induced fluorescence determination of biomedically important phenothiazines in aqueous media at different pH values

Photochemically induced fluorescence studies of 1,3-diethyl-1,3-diphenylurea as stabilizer and its quantitative determination

The photochemically induced fluorescence (PIF) studies of 1,3-diethyl-1,3-diphenylurea or ethyl centralite (EC) as stabilizer have been carried out under various conditions. Influences of solvent type (water, methanol, acetonitrile and chloroform), oxygen dependence and UV irradiation time on the spectroscopic properties of EC were studied. In order to obtain a better understanding of the photochemical mechanism, products were identified by mass spectrometry study. A novel fluorimetric method has been developed for the determination of EC based on the PIF. The method is based on the use of UV irradiation to produce fluorescent derivatives from EC as a non-fluorescent molecule. The determination is carried out by UV irradiation for 4min through measuring the fluorescence intensity in 354nm when an excitation wavelength of 227nm was used. Parameters related to the analytical signal and to the PIF are optimized. The linear range for determination of EC was 4×10(-8) to 2×10(-6)mol L(-1) and the limit of detection (LOD) was 2×10(-8)mol L(-1) with relative standard deviation (R.S.D.) of 3% (n=5). Finally, the proposed method was successfully applied for the determination of EC in real propellant samples and the acquired results were favorably compared to those obtained with HPLC method.

On-line coupling of solid-phase extraction, derivatization reaction and spectrophotometry by sequential injection analysis: Application to trifluoperazine assay in human urine

INTRODUCTION

This study deals with a new methodology of on-line solid-phase extraction (SPE), derivatization reaction and spectrophotometric measurement utilizing sequential injection analysis (SIA) technique. The method was applied for the assay of trifluoperazine in human urine.

METHODS

An SPE procedure was automated to perform sample clean-up, extraction and preconcentration into a homemade microcolumn connected to a SIA manifold. Unlike previous SIA methods, a simple SIA manifold included one syringe pump and one multi-position valve was constructed. This offered simplicity and rapidity to the proposed method (sampling frequency 11 sample h(-1)). Spectrophotometric measurement was based on a fast oxidation of trifluoperazine by Ce(IV) in sulfuric acidic media resulting in a spectrophotometrically detectable chromophore measured at wavelength 500 nm. The SPE procedure was optimized by the univariate method while the derivatization reaction and spectrophotometric measurement were optimized by multivariate methods.

RESULTS

The method was linear in a range of 70-200 ng ml(-1) and accurate with a recovery of 92.7%. Relative standard deviation of repeatability (n=10 in a day) and intermediate precision (n=5 over a week) did not exceed 4.3% indicating satisfactory precision. The limits of detection and quantification were 18.2 and 55.2 ng ml(-1), respectively. The sensitivity of the method was improved by the preconcentration, the use of extended pathlength in the detection device and the optimization of absorbance measurement. The method is selective in the presence of chlordiazepoxide, which is sometimes taken in combination with trifluoperazine.

DISCUSSION

The method is suitable for the application of overdose and therapeutic drug monitoring in human urine.

Development and validation of a capillary electrophoresis method for the determination of phenothiazines in human urine in the low nanogramper milliliter concentration range using field-amplified sample injection

A capillary zone electrophoresis (CZE) method with ultraviolet-visible detection has been established and validated for the determination of five phenothiazines: thiazinamium methylsulfate, promazine hydrochloride, chlorpromazine hydrochloride, thioridazine hydrochloride, and promethazine hydrochloride in human urine. Optimum separation was obtained on a 64.5 cm x 75 microm bubble cell capillary using a buffer containing 150 mM tris(hydroxymethyl)aminomethane and 25% acetonitrile at pH 8.2, with temperature and voltage of 25 degrees C and 20 kV, respectively. Naphazoline hydrochloride was used as an internal standard. Field-amplified sample injection (FASI) has been applied to improve the sensitivity of the detection. Considering the influence of parameters affecting the on-line preconcentration (nature of preinjection plug, sample solvent composition, injection times, and injection voltage) and due to the significant interactions among them, in this paper we propose for the first time the application of a multivariate approach to carry out the study. The optimized conditions were as follows: preinjection plug of water for 7 s at 50 mbar, electrokinetic injection for 40 s at 6.2 kV, and 32 microm of H3PO4 in the sample solvent. Also, a solid-phase extraction (SPE) procedure is developed to obtain low detection limits and an adequate selectivity for urine samples. The combination of SPE and FASI-CZE-UV allows adequate linearities and recoveries, low detection limits (from 2 to 5 ng/mL), and satisfactory precisions (3.0-7.2% for an intermediate RSD %).

Determination of some psychotropic phenothiazine drugs by charge-transfer complexation reaction with chloranilic acid

A spectrophotometric method is described for the determination of four commonly used psychotropic phenothiazine drugs. The method is based on the measurement of the intensely coloured charge-transfer complex formed by the interaction of these drugs as n-electron donors with chloranilic acid as the pi-acceptor. The coloured species measured exhibits maximum absorption at 535 nm. The molar-combining ratio and optimum assay conditions are reported. Beer's law is obeyed over the range, 25-250 microg ml(-1) with apparent molar absorptivity in the range, 0.93 x 10(3)-1.45 x 10(3) l mol(-1) cm(-1). The limits of detection and quantification are reported. The proposed method was applied to the determination of these psychotropics in pharmaceutical formulations and the results demonstrated that the method is equally accurate, precise and reproducible as the official methods. The validity of method was established by recovery studies via standard-addition technique with satisfactory results.

Analysis of Phenothiazine and Its Derivatives Using LC/Electrochemistry/MS and LC/Electrochemistry/Fluorescence

The on-line electrochemical conversion of phenothiazine and its derivatives after liquid chromatographic separation has been studied by mass spectrometry and fluorescence spectroscopy. In an electrochemical cell consisting of porous glassy carbon, the phenothiazines are readily converted to oxidized products, which can be detected by on-line fluorescence spectroscopy and mass spectrometry. The method allows rapid investigations on the electrochemical oxidation pathways, as demonstrated for phenothiazine itself. The phenothiazine derivatives are transferred into their strongly fluorescent sulfoxides. Based on this reaction, an LC/electrochemistry/fluorescence method was developed that allows for limits of detection between 5 x 10(-9) and 4 x 10(-8) mol/L and limits of quantification between 2 x 10(-8) and 1 x 10(-7) mol/L for the individual phenothiazines. The linear ranges comprised three decades starting at the limit of quantification.