Search results for "SOLID-PHASE"
showing 10 items of 178 documents
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…
Miniaturized matrix solid phase dispersion procedure and solid phase microextraction for the analysis of organochlorinated pesticides and polybromina…
2009
Abstract This work has developed a miniaturized method based on matrix solid phase dispersion (MSPD) using C18 as dispersant and acetonitrile–water as eluting solvent for the analysis of legislated organochlorinated pesticides (OCPs) and polybrominated diphenylethers (PBDEs) in biota samples by GC with electron capture (GC-ECD). The method has compared Florisil®-acidic Silica and C18 as dispersant for samples as well as different solvents. Recovery studies showed that the combination of C18–Florisil® was better when using low amount of samples (0.1 g) and with low volumes of acetonitrile–water (2.6 mL). The use of SPME for extracting the analytes from the solvent mixture before the injectio…
Fishing for a drug: solid-phase microextraction for the assay of clozapine in human plasma
1999
Solid-phase microextraction (SPME) was investigated as a sample preparation method for assaying the neuroleptic drug clozapine in human plasma. A mixture of human plasma, water, loxapine (as internal standard) and aqueous NaOH was extracted with a 100-micron polydimethylsiloxane (PDMS) fiber (Supelco). Desorption of the fiber was performed in the injection port of a gas chromatograph at 260 degrees C (HP 5890; 30 m x 0.53 mm I.D., 1 micron film capillary; nitrogen-phosphorous selective detection). Fibers were used repeatedly in up to about 75 analyses. The recovery was found to be 3% for clozapine from plasma after 30 min of extraction. However, in spite of the low recovery, the analyte was…
Automatic in-tube SPME and fast liquid chromatography: A cost-effective method for the estimation of dibuthyl and di-2-ethylhexyl phthalates in envir…
2007
A 80-cm length commercially available capillary coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane (TBR-5) was employed to carry out on-line extraction and preconcentration of dibuthyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) in the chromatographic system. The coated capillary was placed between the sample injection loop and the injection needle of an autosampler. Variables affecting the automatic in-tube solid-phase microextraction (SPME) were optimized. A Genesis C(18) (5 cm x 4.6 mm i.d., 4 microm particle size) was employed as analytical column. The achieved limits of detection by use of diode array detection were 1 and 2.5 microg L(-1), respectively. The propo…
On-line in-tube solid phase microextraction-capillary liquid chromatography method for monitoring degradation products of di-(2-ethylhexyl) phthalate…
2014
Abstract The main di-(2-ethylhexyl) phthalate (DEHP) degradation products, (2-ethylhexyl) phthalate (MEHP), diethyl phthalate (DEP) and dibutyl phthalate (DBP), have been tested. The proposed cost-effective method combines on-line, in-tube solid-phase micro extraction (IT-SPME) in in-valve configuration and capillary liquid chromatography with UV diode array detection (Cap-LC-DAD). Acidification of the samples at pH 3 improved markedly the estimation of MEHP. Aliquots of 4 mL of acidified water samples were directly processed. After sample loading, the analytes were desorbed with the mobile-phase and transferred to the monolithic capillary column. Satisfactory linearity and precision, absen…
Solid-Phase Microextraction Liquid Chromatography/Tandem Mass Spectrometry To Determine Postharvest Fungicides in Fruits
2003
A method to determine five postharvest fungicides (dichloran, flutriafol, o-phenylphenol, prochloraz, tolclofos methyl) in fruits (cherries, lemons, oranges, peaches) has been developed using solid-phase microextraction (SPME) coupled to liquid chromatography (LC) with photodiode array (DAD), mass spectrometry (MS), or tandem mass spectrometry (MS/MS) with ion trap detection. Extraction involved sample homogenization with an acetone/water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. The pesticides were isolated with a fused-silica fiber coated with 50-microm Carbowax/template resin. The effects of pH, ion strength, sample volume, and extraction time were in…
Off-line solid-phase microextraction and capillary electrophoresis mass spectrometry to determine acidic pesticides in fruits.
2003
A method based on solid-phase microextraction (SPME) and capillary electrophoresis/mass spectrometry (CE/ MS) is described for determining simultaneously five acidic pesticides (o-phenylphenol, ioxynil, haloxyfop, acifluorfen, picloram) in fruits. The CE device is coupled to an electrospray interface by a commercial sheath-flow adapter. Emphasis is placed on fulfillment of the speed and sensitivity requirements. The best separation is achieved using 32 mM ammonium formate/acid formic buffer at pH 3.1, with a working voltage of 25 kV. The MS detection of the five pesticides was performed in negative ionization mode. Full-scan spectra with base peaks corresponding to [M-H]- were obtained exce…
A headspace solid-phase microextraction method of use in monitoring hexanal and pentane during storage: Application to liquid infant foods and powder…
2006
The determination of two secondary lipid oxidation compounds (hexanal and pentane) in liquid infant foods using a headspace solid-phase microextraction gas chromatographic (HS-SPME-GC) method has been developed and validated. The HS-SPME analytical conditions (fibre position, equilibration and sampling times) were selected. The analytical parameters of the method (linearity: hexanal from 2.48 to 84.78 ng/g, pentane from 6.21 to 79.55 ng/g; precision: hexanal 2.87%, pentane 2.343.46%; recovery: hexanal 106.60%, pentane 95.39%; detection limit: hexanal 3.63 ng and pentane 4.2 ng) demonstrate the usefulness of the method. Once optimized, the method was applied to liquid infant foods based on m…
In-tube solid-phase microextraction and liquid chromatography using a monolithic column for the selective determination of residual ethylenediamine i…
2009
The selective determination of the diamine ethylenediamine (EDA) in the presence of a higher amount of residual dimethylamine in cationic polymers has been developed. The strategy uses both a solution derivatization with a selective agent of primary amines such as o-phthaldialdehyde-N-acetyl-L-cysteine (OPA-NAC) and an in-tube solid-phase microextraction (IT-SPME) coupled to liquid chromatography (LC). A 70 cm long, 0.32 mm internal diameter, and 3 microm thick commercially available capillary column coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane was employed to replace the injection loop of a Rheodyne injection valve. A volume of 1 mL of derivatized sample was passed thro…
A cost-effective method for estimating di(2-ethylhexyl)phthalate in coastal sediments.
2013
This study describes the development of a new method for the analysis of di(2-ethylhexyl)phthalate (DEHP) using 0.1-0.3 g of sediment sample, based on matrix solid phase dispersion (MSPD) using C18 as dispersant phase (0.4 g) and acetonitrile-water as eluting solvent (3.4 mL 1:3.25, v/v). No evaporation step is required. 3 mL of extracts were processed on-line by in-tube solid phase microextraction (IT-SPME) coupled to capillary liquid chromatography (CapLC) and diode array detector (DAD). A short analytical column Zorbax SB C18 (35×0.5 mm, 5 μm) provided suitable results. FTIR-ATR was employed for characterizing sediment samples and MSPD procedure. The total analysis time was less than 20 …