Search results for "Derivatization"
showing 10 items of 215 documents
Analysis and fractionation of natural source diacylglycerols as urethane derivatives by reversed-phase high-performance liquid chromatography
1991
Abstract Reversed-phase high-performance liquid chromatography on a thermostatted octadecylsilyl column was used to separate and fractionate mixtures of diacylglycerols after derivatization with 3,5-dinitrophenyl isocyanate (urethane derivatives). In addition to the separation of commercial diacylglycerol species, the separation of diacylglycerols obtained from peanut oil and cottonseed oil triacylglycerols by chemical hydrolysis is reported. Acetonitrile-acetone mixtures were used for elution of the diacylglycerol urethane derivatives. Unsaturated and saturated derivatives were detected by their refractive indices. They were then collected and their fatty acids analysed as methyl esters by…
Separation of monoacylglycerols by reversed-phase high-performance liquid chromatography
1992
Abstract Reversed-phase high-performance liquid chromatography on a thermostated octadecylsilyl column was used to separate complex mixtures of monoacyglycerols formed by chemical deacylation of natural triacyclycerols. Acetonitrile-water mixtures were used for elution of the underivatized monoacylglycerols and a different refractometer was used for their detection. The order of elution of monoacylglycerols in complex mixtures varies as a function of the chain length, unsaturation, positional isomerism, analysis temperature and eluent water concentration. The peak areas were representative of the amounts of monoacylglycerols detected. The method can be applied to compositional analysis and …
New optical paper sensor for in situ measurement of hydrogen sulphide in waters and atmospheres
2016
A novel and low-cost colorimetric sensor for the determination of hydrogen sulphide in environmental samples has been developed. This sensor is based on the immobilization of the reagent N,N-Dimethyl-p-phenylenediamine and FeCl3 in paper support, in which the H2S is adsorbed in order to give rise to the formation of methylene blue as reaction product. The sensor has been applied to determine H2S in water and air samples. Two different sampling systems for H2S caption from the air have been assayed: active and passive sampling. The analytical properties of the different systems have been obtained and compared. The analytical signals, corresponding to the methylene blue, have been obtained me…
On-line analysis of carbonyl compounds with derivatization in aqueous extracts of atmospheric particulate PM10 by in-tube solid-phase microextraction…
2011
Abstract A new device for carbonyl compounds based on coupling on-line and miniaturizing both, sample pretreatment and chromatographic separation, is reported. Two capillary columns, a GC capillary column (95% methyl–5% phenyl substituted backbone, 70 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve for in-tube solid-phase microextraction (IT-SPME) and a Zorbax SB C18 (150 mm × 0.5 mm i.d., 5 μm particle diameter) LC capillary column were employed. Different combinations of IT-SPME and derivatization using 2,4-dinitrophenylhydrazine (DNPH) were examined for mixtures containing 15 carbonyl compounds (aliphatic, aromatic and unsaturated aldehydes and ketones). A screening analys…
Liquid Chromatographic Analysis of Amphetamine and Related Compounds in Urine Using Solid-Phase Extraction and 3,5-Dinitrobenzoyl Chloride for Deriva…
1997
A chromatographic method for the analysis of amphetamine and related compounds in urine using 3,5-dinitrobenzoyl chloride (3,5-DNB) as a labeling reagent is presented. This assay is based on the employment of solid-phase extraction (SPE) cartridges for sample cleanup and derivatization. Experimental conditions are optimized for the simultaneous derivatization of ephedrine, norephedrine, pseudoephedrine, beta-phenylethylamine, amphetamine, methamphetamine, and 3-phenylpropylamine. The derivatives formed are separated in a LiChrospher 1000 RP18 (125 x 4-mm i.d., 5-microns film thickness) analytical column using a water-acetonitrile gradient elution and detected at 254 nm. Derivatization in C1…
Analysis of methylamine by solid-phase microextraction and HPLC after on-fibre derivatization with 9-fluorenylmethyl chloroformate
2004
Abstract A method for the determination of methylamine (MA) in aqueous matrices is reported which uses solid-phase microextraction (SPME) for enrichment and derivatization of the analyte, and high performance liquid chromatography (HPLC). The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) has been used for derivatization. The SPME fibres were successively immersed in the samples and in the derivatization solutions to extract MA and FMOC, respectively. After a defined time of reaction, the derivatized analyte was desorbed into the chromatographic system, and chromatographed in a LiChrosphere 100 RP18, 125 mm ×4 mm i.d., 5 μm, column under gradient elution. In order to improve the…
Automated high-performance liquid chromatographic determination of amphetamine in biological fluids using column-switching and on-column derivatizati…
1999
A rapid and simple liquid-chromatographic method has been developed for on-line quantification of amphetamine in biological fluids. Untreated samples (20 μL) are injected directly into the chromatographic system and purified on a 20 mm×2.1 mm i.d. pre-column packed with 30 μm Hypersil C18 stationary phase. After clean-up the analyte is transferred to the analytical column (125 mm×4 mm i.d., 5 μm LiChrospher 100 RP18) for derivatization and separation using a mixture of acetonitrile and the derivatization reagent (o-phthaldialdehyde andN-acetyl-L-cysteine) as the mobile phase. The experimental conditions for on-line derivatization and resolution of the amphetamine have been optimized, and th…
Determination of alternative preservatives in cosmetic products by chromophoric derivatization followed by vortex-assisted liquid-liquid semimicroext…
2016
An analytical method for the simultaneous determination of phenethyl alcohol, methylpropanediol, phenylpropanol, caprylyl glycol, and ethylhexylglycerin, which are used as alternative preservatives in cosmetic products, has been developed. The method is based on liquid chromatography with UV spectrophotometric detection after chromophoric derivatization with benzoyl chloride and vortex-assisted liquid-liquid semimicroextraction. Different chromatographic parameters, derivatization conditions, and sample preparation variables were studied. Under optimized conditions, the limits of detection values for the analytes ranged from 0.02 to 0.06µgmL(-1). The method was validated with good recovery …
A new selective method for dimethylamine in water analysis by liquid chromatography using solid-phase microextraction and two-stage derivatization wi…
2005
Abstract A new method is presented for the determination of DMA in water as its 9-fluorenylmethyl chloroformate (FMOC) derivative using solid-phase microextraction (SPME) and liquid chromatography. The method is based on the employment of SPME fibres coated with carbowax-templated resin (CW-TR) for analyte extraction and derivatization. The fibres were successively immersed in the samples, in a solution of o -phthalaldialdehyde and N -acethyl- l -cysteine (OPA–NAC) and finally, in a solution of FMOC. OPA–NAC reacted on the fibre with possible primary aliphatic amines present in the samples, particularly with PA which is a direct interferent in the determination of DMA with FMOC. In such a w…
Bromine speciation in volcanic plumes: new in situ derivatization LC-MS method for the determination of gaseous hydrogen bromide by gas diffusion den…
2020
The chemical characterization of volcanic gas emissions gives insights into the interior of volcanoes. Monitoring of BrO/SO2-ratios has recently been correlated with changes in the activity of a volcano. BrO and SO2 can both be measured autonomously and simultaneously with the same instruments from a safe distance, making their ratio potentially a strong monitoring tool. However, BrO is not a primary emitted volcanic volatile and there exist still uncertainties about the formation of BrO in volcanic plumes, mostly due to the lack of analytical approaches for the accurate speciation of certain key compounds. This study describes a new method for the determination of the BrO precursor, the ga…