Search results for "solid phase"
showing 10 items of 360 documents
Determination of microcystins in biological samples by matrix solid-phase dispersion and liquid chromatography–mass spectrometry
2005
A method for the detection and quantification of the microcystins (MCs)-MC-LR, MC-RR and MC-YR-in biological samples by matrix solid-phase dispersion (MSPD) has been developed. The optimum extraction conditions were 500 mg of liver or kidney, C18 bonded silica as dispersant, and a mixture methanol-water (70:30) as eluent. The MCs were determined by liquid chromatography electrospray mass spectrometry (LC/ES/MS). Recoveries of biological extracts at three different spiked levels (1-10 mg kg(-1)) ranged from 40.5 to 87.0% in liver, and from 52.5 to 74.5 in kidney. R.S.D.s were < 15.6% and < 10.6%, respectively. The detection and quantification limits were 0.05 and 0.5 mg kg(-1), for all MCs. …
Investigation of cuticular hydrocarbons from Bagrada hilaris genders by SPME/GC-MS
2007
The cuticular hydrocarbons of male and female Bagrada hilaris Burmeister (Heteroptera: Pentatomidae) were investigated, by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry. Measurements were done with fiber coatings of different polarity after optimization of headspace volumes and extraction temperatures. This resulted in the use of polyacrylate fiber, 22-ml vial as the sample holder, and an extraction temperature of 150 degrees C. The analytical procedures allowed identification of 13 peaks, corresponding to a homologous series of n-alkanes (nC(17)-nC(29)). The hydrocarbon profiles of male and female B. hilaris were qualitatively equal, but marked sex-…
Targeting metabolomics analysis of the sunscreen agent 2-ethylhexyl 4-(N,N-dimethylamino)benzoate in human urine by automated on-line solid-phase ext…
2011
The in vivo metabolism of the xenobiotic agent 2-ethylhexyl 4-(N,N-dimethylamino)benzoate (EDP), a UV filter commonly used in sunscreen cosmetic products, was studied by targeting metabolomics analysis in human urine. The metabolomic study involved the use of urine from male and female volunteers before and after application of an EDP-containing sunscreen cosmetic. The metabolism of EDP in urine was studied by using the triple quadrupole detector in a combination of Precursor Ion Scanning and Neutral Loss Scanning modes, with and without enzymatic hydrolysis. Detected metabolites were subsequently confirmed as glucuronide conjugates of 4-(N,N-dimethylamino)benzoic acid and 4-(N-methylamino)…
De novo Synthesis of Chemical Defenses in an Aposematic Moth.
2018
Abstract Many animals protect themselves from predation with chemicals, both self-made or sequestered from their diet. The potential drivers of the diversity of these chemicals have been long studied, but our knowledge of these chemicals and their acquisition mode is heavily based on specialist herbivores that sequester their defenses. The wood tiger moth (Arctia plantaginis, Linnaeus, 1758) is a well-studied aposematic species, but the nature of its chemical defenses has not been fully described . Here, we report the presence of two methoxypyrazines, 2-sec-butyl-3-methoxypyrazine and 2-isobutyl-3-methoxypyrazine, in the moths’ defensive secretions. By raising larvae on an artificial diet, …
Innovations in Extractive Phases for In-Tube Solid-Phase Microextraction Coupled to Miniaturized Liquid Chromatography: A Critical Review
2020
Over the past years, a great effort has been devoted to the development of new sorbents that can be used to pack or to coat extractive capillaries for in-tube solid-phase microextraction (IT-SPME). Many of those efforts have been focused on the preparation of capillaries for miniaturized liquid chromatography (LC) due to the reduced availability of capillary columns with appropriate dimensions for this kind of system. Moreover, many of the extractive capillaries that have been used for IT-SPME so far are segments of open columns from the gas chromatography (GC) field, but the phase nature and dimensions are very limited. In particular, polar compounds barely interact with stationary GC phas…
Recent applications of carbonaceous nanosorbents for the analysis of mycotoxins in food by liquid chromatography: a short review
2019
Carbonaceous nanomaterials (multi-walled carbon nanotubes (MWCNTs), graphene, and graphene oxide (GO)) have attracted attention over the last decade as adsorbents suitable for the analysis of organic and inorganic pollutants. In the present paper we review methods of mycotoxin analysis that involve sample extraction with carbonaceous nanosorbents, reported from 2011 onwards. Recent studies have highlighted the advantages of magnetically modified MWCNTs and GO in mycotoxin analysis, which may enable sample isolation through magnetic separation, reduce the interaction of nanoparticles, and enhance the recovery of analytes. The papers covered in this review point to promising applications of …
The Effect of Technological Factors on the Synthesis of PbMg 1/3 Nb 2/3 O 3
2003
Conventional technique of solid phase reactions allows one to obtain PbMg 1/3 Nb 2/3 O 3 material with about 20 vol.% of the pyrochlore phase. The latter can be reduced to 5 vol.% by Swartz-Shrout two-stage solid state reaction via MgNb 2 O 6 having the columbite structure. A single-phase perovskite product can be obtained by by the two-stage columbite method from mixtures containing 0.2 mol. parts of overstoichiometric MgO. The best results are obtained by using magnesium carbonate hydroxide pentahydrate (MgCO 3 ) 4 ·Mg(OH) 2 ·5H 2 O as the magnesium source. The modified route yields stoichiometric single-phase PMN.
Microextraction with phases containing nanoparticles.
2015
In this article, the state of the art of microextraction techniques that involve nanoparticles or nanomaterials (NPs) is reviewed, with special emphasis on the applications described in the biomedical field. The uses and advantages of the different types of NPs such as carbon nanotubes (either single- and multi-walled) and other carbon-based materials, metallic NPs, including gold, silver and magnetic NPs, and silica NPs are summarized. The main strategies used to modify the selectivity, extractive capacity and/or the stability of NPs through a chemical reaction are also reviewed. The potential advantages of NPs in different forms of off-line and on-line microextraction are discussed, and …
Evaluation of a Multidimensional Solid-Phase Extraction Platform for Highly Selective On-Line Cleanup and High-Throughput LC−MS Analysis of Triazines…
2001
A novel highly selective sample cleanup procedure based on the use of molecularly imprinted polymers (MIPs) as solid-phase extraction materials has been evaluated with respect to its applicability and routine use in environmental analysis. The method comprises the combination of a restricted access material (RAM) and a MIP allowing a selective sample preparation to be achieved in the online mode. This combination is called the size-selective sample separation and solvent switch (six-SPE). The RAM column combines size exclusion and adsorption chromatography, reducing the concentration of matrix molecules by a cutoff of 15 kDa. The MIP column selectively retains the triazine analytes whereas …
Solid phase techniques in the extraction of pesticides and related compounds from foods and soils
1994
The application of SPE technology to the isolation of pesticides and related compounds from food and soils has grown enormously in the last decade. Much of this growth has been due to the relative ease of sample handling and the wide range of solid supports currently available for a variety of applications. The aim of this review is to present the methods for solid phase extraction (SPE) of pesticide residues from soils and foods. There are three main areas according to the type of approach used to handle the sample: solid phase extraction, solid phase clean-up (SPC), and matrix solid phase dispersion (MSPD). This review covers milk products, fatty foods, fruits, vegetables, and soils. Soli…