Search results for "solid phase"
showing 10 items of 360 documents
Preconcentration and dansylation of aliphatic amines using C18 solid-phase packings
2002
Abstract Precolumn preconcentration and derivatization on solid sorbents (Bond Elut C18 solid-phase extraction cartridges) of low-molecular-mass aliphatic amines in water samples have been performed using dansyl chloride (Dns-Cl) as derivatization reagent. Conditions for analyte preconcentration and derivatization such as volume sample, reagent concentration, time, pH and temperature reaction were optimised. On the basis of these studies a rapid and sensitive method for screening of aliphatic amines in waters is presented. Up to volumes of 5 ml, samples are drawn through the sorbent, the analytes retained are dansylated at basic pH, at 100 °C for 10 min or 85 °C for 15 min. The derivatized …
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 …
Rapid screening of organophosphorus pesticides in honey and bees by liquid chromatography—Mass spectrometry
2002
Twenty-two organophosphorus pesticide residues were simultaneously determined in honey and honeybee samples by extraction procedures based on solid-phase and liquid chromatography-atmospheric pressure chemical ionization-mass in positive and negative ionization modes. Pesticides in honeybee samples were extracted by matrix solid phase dispersion with C18 silica and subsequently eluted with a mixture of dichloromethane-methanol (85∶15, v/v). The average recoveries from spiked honeybees (0.5–10 μg g−1) ranged from 76% for coumaphos to 100% for omethoate, with relative standard deviations between 3 and 17%. Limits of detection were ≤0.13 μg g−1 and limits of quantification were ≤0.43 μg g−1. H…
Automated on-line in-tube solid-phase microextraction-assisted derivatization coupled to liquid chromatography for quantifying residual dimethylamine…
2008
Abstract A method for the analysis of dimethylamine (DMA) by automated in-tube solid-phase microextraction (IT-SPME)-supported chemical derivatization coupled with high-performance liquid chromatography was developed. Extraction, derivatization and desorption were studied by using a capillary coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane. Solution derivatization and automated IT-SPME derivatization using 9-fluorenylmethyl chloroformate (FMOC) were compared. The proposed procedure provided adequate linearity, accuracy and precision in the 0.2–2.0 μg/mL concentration interval, and the limit of detection (LOD) was 50 ng/mL. The main advantages of the proposed procedure are: …
Determination of pesticides in soil samples by solid phase extraction disks
1993
A systematic study comparing the methodology and analytical results obtained in an investigation of seven pesticide residues (Molinate, Atrazine, Carbofuran, Pirimicarb, Prometryn, Malathion and Tetrachlorvinphos) in soil samples is reported. Solid-phase extraction (SPE) using glass columns and 47 mm disks of octyl and octadecyl-bonded silica was used in the pesticide analysis. The best extraction efficiency and clearest extracts are obtained with C8 disks. The analyses were carried out by capillary gas chromatography with nitrogen and phosphorus detection. Recovery experiments were performed at ppb levels in spiked soil samples. The average recoveries of the compounds were 53–77%. Detectio…
Amphetamine and methamphetamine determination in urine by reversed-phase high-performance liquid chromatography with sodium 1,2-napthoquinone 4-sulfo…
1995
A rapid method is described for the identification and determination of amphetamine and methamphetamine in human urine samples by liquid chromatography with UV-Vis detection. The samples were transferred onto a C18 solid-phase extraction column and chromatographed on a Hypersil ODS RP C18, 5 microns (250 x 4 mm I.D.) with an acetonitrile-water elution gradient containing propylamine. Under these conditions, the amines are eluted with a short retention time. The procedure has been applied to the determination of amphetamine and methamphetamine in the range 0.3-4.0 micrograms/ml in spiked urine samples. The detection limits at 280 nm were 4 and 2 ng/ml for amphetamine and methamphetamine, res…
Automated Determination of Trimipramine and N-Desmethyl-Trimipramine in Human Plasma or Serum by HPLC With On-Line Solid Phase Extraction
1995
A fully automated method including column-switching and isocratic high performance liquid chromatography (HPLC) was developed for determination of the tricyclic antidepressant trimipramine (T) and its N-demethylated metabolite N-desmethyltrimipramine (DT). The limit of quantification was below 10 ng/ml for T and DT. The assay revealed linearity between detector response and drug concentration in a therapeutically relevant range of 10 to 500 ng/ml. The mean intra- and interassay variabilities were 6.2 and 12.3%, respectively, for T and 4.7 and 8.7% respectively, for DT. The method can be applied to therapeutic drug monitoring of patients under T therapy and may be useful for pharmacokinetic …
Matrix effects on solid-phase microextraction of organophosphorus pesticides from water
1997
Abstract This study develops a method for solid-phase microextraction (SPME) of eight organophosphorus pesticides, diazinon, fenthion, fenitrothion (sumithion), methyl-parathion, parathion, methyl-trithion, ethion and triazophos, from water. Determination is carried out by gas chromatography with nitrogen-phosphorus detection. To perform the SPME, poly(dimethylsiloxane) and polyacrylate fibers were initially compared on the basis of their absorption capacities for the selected pesticides, and polyacrylate was selected to accomplish the rest of assays. The main factors affecting the SPME process such as memory effect, stirring rate, extraction temperature and absorption-time profile were stu…