Mobile Phase Of Ethanol Research Articles

Supercritical fluid extraction and high performance liquid chromatography determination of homosalate in lipsticks

Supercritical fluid extraction of homosalate is reported for the first time. Extraction parameters such as pressure, time of extraction, use of modifier, temperature and sample mass were studied. The proposed method was assayed for the extraction of homosalate in sunscreen lipsticks. Efficient recoveries were obtained after 5 min of dynamic extraction with supercritical CO2 and 15% ethanol as modifier at 300 bar and 60°C, flow rate 4 mL min−1. Extracts were dissolved in ethanol, and homosalate determined by HPLC using water—acetic acid—ethanol mobile phase and flow rate of 1 mL min−1. UV detection was at 309 nm using homosalate in ethanol solutions as standards, limit of detection 4 μg mL−1. The RSD was 0.4–1.0%. The results were comparable to real concentrations of samples and values by HPLC after dissolution of samples using tetrahydrofuran. The method, based on SFE, invovees low solvent consumption and, can therefore be considered a green procedure.

Determination of the UV filters worldwide authorised in sunscreens by high-performance liquid chromatography: Use of cyclodextrins as mobile phase modifier

Simultaneous determination of organic UV filters worldwide authorised in sunscreen formulations was performed by HPLC with UV spectrophotometric detection. The filters determined were: benzophenone-4, benzophenone-3, butyl methoxydibenzoylmethane, octyl dimethyl PABA, octyl methoxycinnamate, homosalate and octyl salicylate. A C 18 stationary phase and an isocratic mobile phase of ethanol–water–acetic acid (70:29.5:0.5) containing 65.4 m M of hydroxypropyl-β-cyclodextrin, were used with a flow-rate of 0.6 ml/min. UV measurements were carried out at 313 nm. The time required for the analysis was 20 min and the limits of detection were between 1.5 and 2.3 mg/l. The procedure proposed provides a green analytical method with a basic instrumental configuration, it is fast and accurate and does not involve highly toxic organic solvents.

LIQUID CHROMATOGRAPHIC DETERMINATION/IDENTIFICATION OF RESIDUAL PENICILLIN G IN FOOD-PRODUCING ANIMAL TISSUES

A simple and rapid high performance liquid chromatographic (HPLC) determination of residual penicillin G (benzylpenicillin, PCG) in cattle, pig, and chicken tissues (muscle, kidney, and liver) was developed. The sample preparation was performed by homogenizing with 0.1 M phosphate buffer (pH 6.5) followed by an Ultrafree®-MC/PL as a centrifugal ultrafiltration unit. For determination/identification of PCG, a Mightysil® RP-4GP column and a mobile phase of ethanol—0.1 M phosphate buffer (pH 6.5) (1:4, v/v) with a photodiode array detector was used. The average recoveries from spiked PCG (0.05, 0.1, 0.5, and 1.0 ppm) were in excess of 78.8% with coefficients of variation between 1.6 and 4.9%. The limit of detection was 0.04 ppm. The total time and solvent required for the analysis of one sample was <40 min and <2 mL of ethanol, respectively.

Development and Validation of a Chiral HPLC Method for the Quantitation of Methocarbamol Enantiomers in Human Plasma

Abstract An isocratic chiral HPLC method was developed and validated for the quantitation of methocarbamol enantiomers in human plasma. Methocarbamol and an internal standard were extracted with ethyl ether. Chiral separation was achieved on coupled Spherisorb CN and Chiralcel OD columns with a mobile phase of ethanol—hexane (30:70, v/v). The detection was by UV at 272 nm. Linearity was established at 0.5–50 μg/ml (r < 0.998). Interday precision and accuracy of the calibration standards were demonstrated by 0.8 to 9.4% coefficients of variance (C.V.) and −5.2 to +3.8% relative error (R.E.). Quality controls showed interday precision and accuracy of 4.4 to 7.2% C.V. and +0.4 to +5.5% R.E. Recovery of methocarbamol enantiomers was 77–84%. No interconversion of the methocarbamol enantiomers was observed during process of storage, extraction nor chromatograph. Reproducibility and stability of the analytical columns were demonstrated.

Application of high-performance liquid chromatographic separation of free sterols to the screening of yeast sterol mutants

A method for the rapid separation of free sterols by reversed-phase liquid chromatography has been developed. A trinary mobile phase of ethanol, methanol, and water pumped through an ODS (octadecylsilane)-Ultrasphere column allowed for the separation of sterols on the basis of the number and location of double bonds and alkyl groups. This method is utilized to screen yeast mutants for altered sterol patterns.

Reverse phase thin-layer chromatographic separation of bromodiphenhydramine and diphenhydramine.

A thin-layer chromatographic system is described for the separation of diphenhydramine and bromodiphenhydramine which is based on a reverse phase paper chromatographic system developed by J. Vecerková (2,3) in 1962. Chromatographic systems for this separation described in the literature and several systems attempted in this laboratory using normal chromatography have not proven successful. The method using reverse phase thin-layer chromatography involves a stationary phase of mineral oil on silica gel G and a mobile phase of ethanol:water:ammonium hydroxide, 28% NH3, (55:43:2). A 10-cm length of run requires about three hours and provides an excellent separation of the two compounds for identification-differentiation purposes.