Search results for "Extraction"
showing 10 items of 2072 documents
Development and Validation of a Reversed-Phase Liquid Chromatography Method for the Simultaneous Determination of Indole-3-Acetic Acid, Indole-3-Pyru…
2011
A simple, sensitive, precise, and specific reverse HPLC method was developed and validated for the determination of plant hormones in barley (Hordeum vulgareL.). The method includes extraction in aqueous organic solvent followed by solid-phase extraction, sample evaporation, and reversed-phase HPLC analysis in a general purpose UV-visible (abscisic acid (ABA)) and fluorescence detection (indole-3-acetic acid (IAA) and indole-3-pyruvic acid (IPA)), high-performance liquid chromatography system. The separation was carried out on Zorbax Eclipse XDB C8 column (150 × 4.6 mm I.D) with a mobile phase composed of methanol and 1% acetic acid (60 : 40 v/v) in isocratic mode at a flow rate of 1 ml min…
An environmentally friendly multicommutated alternative to the reference method for anionic surfactant determination in water
2004
Abstract It has been developed a fully mechanized procedure for the spectrophotometric determination of anionic surfactants in water expressed in terms of SDS concentration. The reference method, based on the reaction of SDS with methylene blue (MB) followed by extraction in chloroform, was mechanized in order to reduce the consumption of organic solvents. The system was based on the multicommutation approach and provided a 35 times reduction of the waste production without sacrificing the figures of merit of the method in terms of sensitivity and repeatability, for a dynamic linear range from 0.2 to 1.7 mg l−1. Results obtained for washing water samples were comparable with those obtained …
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 …
Extractive-spectrophotometric determination of amphetamine in urine samples with sodium 1,2-naphthoquinone 4-sulphonate
1993
Abstract Sodium 1,2-naphthoquinone 4-sulphonate (NQS) was tested as a reagent for amphetamine in order to develop an extractive-spectrophotometric method for the drug in urine samples. The standard additions method showed the absence of proportional bias error whereas the Youden method and the two standard addition plots method showed the presence of a constant bias error [total Youden blank (TYB)]. Acceptable results were obtained by evaluating the TYB error or by using a placebo (urine sample from a normal subject). The dynamic range of concentrations was 1.4–50 mg 1−1 in urine samples and the detection limit was 0.6 mg 1−1 when 10 ml of urine sample were taken.
Determination of inorganic species by thermal lens spectrometry
1997
Abstract The application of thermal lens spectrometry (TLS) to the determination of inorganic species is reviewed. The requirements of a chromogenic reaction to be advantageously adapted to TLS detection, and the necessary conditions for reaching very low limits of detection are discussed. Methods for the determination of metals and P, Si, S and N compounds in several samples are examined. Flow-injection and extraction methods, associated photoinduced reactions and surface phenomena, speciation and equilibrium studies are discussed. Gas phase NO 2 methods are also commented upon. Trends are given.
Improving detection limits for organotin compounds in several matrix water samples by derivatization-headspace-solid-phase microextraction and GC-MS.
2010
Triethyltin, tributyltin, diphenyltin and triphenyltin were selected as model compounds. The method is based on in situ ethylation and simultaneous headspace-solid-phase microextraction (HS-SPME) and gas chromatographic-mass spectrometry analysis (GC-MS). The extraction procedure was optimized studying some variables such as reaction time, salinity, sample volume and headspace volume. SPME-GC-MS and SPME-GC-FID techniques were compared; quality assurance parameters such as sensitivity, selectivity and precision were established. The proposed procedure showed limits of detection between 0.025 and 1 ng/L. The linearity was in the 0.025-5000 ng/L range. The precision expressed as relative stan…
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…
Pressurised liquid extraction and capillary electrophoresis–mass spectrometry for the analysis of pesticide residues in fruits from Valencian markets…
2010
Abstract A procedure based in capillary electrophoresis–mass spectrometry (CE–MS) for the analysis of seven pesticides (flutolanil, simazine, haloxyfop, acifluorfen, dinoseb, picloram, and ioxynil) in four Mediterranean summer fruits with high water content (peaches, melon, watermelon, and apricot) is developed. Several conditions were studied for the optimisation of both, the separation and the electrospray (ESI) connection. The best results were obtained using 35 mM ammonium formiate (pH 9.7) as separation buffer, 20 °C as capillary temperature and 23 kV as applied voltage in an uncoated fused-silica capillary with 50 cm total length, 25 cm thermostated length, 25 cm at room temperature l…
Minimizing the impact of sample preparation on analytical results: In-tube solid-phase microextraction coupled on-line to nano-liquid chromatography …
2020
The degradation kinetics and residual levels of the sulfonylurea herbicide tribenuron-methyl (TBM) in different environmental waters were studied using in tube-solid phase microextraction (IT-SPME) coupled on-line to nano-liquid chromatography (nanoLC) and UV diode array detection (DAD). This approach combines the high extraction efficiency of IT-SPME using polymeric coatings reinforced with metal oxide nanoparticles and the high sensitivity attainable by nanoLC, making possible the determination of TBM at low ppb levels (limit of detection, 0.25 ppb) without altering the sample matrix. The present study demonstrated that the preservation of the sample properties is essential to ensure accu…
Analysis of Polycyclic Aromatic Hydrocarbons and Their Oxygen-Containing Derivatives and Metabolites in Soils
2010
Although polycyclic aromatic hydrocarbons (PAHs) have been extensively studied, the knowledge of their oxygen-containing derivatives and metabolites (OPAHs) in soils is limited. We modified and tested an existing analytical protocol involving pressurized liquid extraction of soil followed by fractionation of target compounds into PAHs and OPAHs on a silica gel column and gas chromatography/ mass spectrometry-based separation and quantification. Polycyclic aromatic hydrocarbons and carbonyl-OPAHs were quantified directly after separation on silica gel columns, and hydroxyl/carboxyl-OPAHs were quantified after silylation with N,O-bis(trimethylsilyl)trifluoroacetamide. Recoveries between 78 an…