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1.
JPC – Journal of Planar Chromatography – Modern TLC - The dansyl derivatives of N-nitrosodimethylamine, N-nitrosodi-ethylamine, and N-nitrosodibuthylamine have been separated by HPTLC... 相似文献
2.
Calbiani F Careri M Elviri L Mangia A Pistarà L Zagnoni I 《Journal of chromatography. A》2004,1042(1-2):123-130
An accurate method based on the use of reversed-phase (RP) liquid chromatography-tandem mass spectrometry interfaced with electrospray (LC-ESI-MS/MS) was devised for the determination of Sudan I, Sudan II, Sudan III and Sudan IV in hot chilli food samples. A simple sample treatment procedure entailing the use of an extraction step with acetone without clean-up was developed. A C18 column with an aqueous formic acid/methanol mixture as the mobile phase was used under isocratic conditions. Mass spectral acquisition was done in positive ion mode by applying selected reaction monitoring of three fragmentation transitions per compound to provide a high degree of selectivity. The method was in-house validated in terms of detection limits (LOD), quantitation limits (LOQ), linearity, sensitivity, accuracy, recovery, and selectivity on two kinds of hot chilli sauces. Good results in the low ng/g level were obtained for LOD and LOQ of all analytes in matrices. Under both intra-day repeatability (R.S.D. between 1 and 13%) and intermediate precision (about 5-15% R.S.D. for both chilli sauce matrices) conditions, precision proved to be typical of determinations based on electrospray LC-MS and acceptable for routine monitoring purposes. Extraction recoveries for all four azo-dyes in chilli tomato sauce ranged from 92 to 103% at a spiking level of 5 microg/kg, whereas values between 72 and 97% were calculated in chilli tomato and cheese sauce at the same concentration level. The applicability of the method to the determination of Sudan azo-dyes in hot chilli products was demonstrated. 相似文献
3.
This work describes the utilization of the focused microwave-assisted micellar extraction in combination with the solid-phase microextraction (SPME) to determine chlorophenols in wood samples. The influence of the nature of the surfactant in the extraction process, the optimization of the variables of the focused-microwave system, and the effect of the ageing time of the samples in the extraction efficiency of the method, have been assessed in this study. The overall method using the non-ionic surfactant POLE as extracting medium allows us to determine chlorophenols in wood samples achieving an average extraction efficiency of 104.1%, limits of detection ranging from 2 to 120 ng g−1, and intermediate precision values ranging between 3.5 and 13.2%. The proposed method is also characterized by short analysis times (around 5 min for the microwaves extraction step) and by avoiding the use of organic solvents. 相似文献
4.
The interaction of 1-naphthol-N-methyl-carbamate (carbaryl) and its degradation product, 1-naphthol, with the surfactant hexadecyl-trimethylammonium bromide has been studied. The micellar medium allows the direct spectrofluorimetric determination of carbaryl, with 6.2 ng/ml as detection limit in acidic medium, or indirectly, after hydrolysis, as 1-naphthol at pH 11.0 or pH 3.0 with detection limits of 0.4 and 1.6 ng/ml, respectively. The recoveries of carbaryl and 1-naphthol from natural waters are acceptable. 相似文献
5.
Solid-phase microextraction coupled with high-performance liquid chromatography for the analysis of heterocyclic aromatic amines 总被引:3,自引:0,他引:3
Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) with UV diode array detection (DAD) for the analysis of heterocyclic aromatic amines (HAs) is described. Four kinds of fiber coatings: Carbowax-templated resin (CW-TPR), Carbowax-divinylbenzene (CW-DVB), poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) and polyacrylate (PA) were evaluated for extraction of nine most biologically active heterocyclic aromatic amines. Different parameters affecting to the microextraction and determination of HAs were studied, such as absorption and desorption time, desorption mode, composition of the solvent for desorption, pH, ionic strength, and percentage of methanol in the sample. To determine these amines in food samples a new simplified procedure is proposed, consisting of treatment of the sample with methanolic NaOH prior microextraction by CW-TPR fiber coating and HPLC-DAD determination. The advantages of this new method are the reduced amounts of time and organic solvents required. 相似文献
6.
Argelio González Rosa M. Linares Juan H. Ayala Ana M. Afonso Venerando González 《Mikrochimica acta》1995,118(3-4):153-162
The effect of cationic micelles of benzyldimethylhexadecylammonium chloride and hexadecyltrimethylammonium bromide on the fluorescence spectra of indole and its carboxylic derivatives were determined. The larger solute-micelle binding constants were provided by benzyldimethylhexadecylammonium chloride, ranging from 0.10·105 and 2.15·105
M
–1 for indole-5-carboxylic and indole-2-carboxylic acid, respectively. The determination of indole-4-carboxylic acid with a detection limit of 1.0 ng ml–1, in the presence of the 3-and 5-substituted derivatives, shows the analytical potential of the synchronous spectrofluorimetry combined with the enhancement effects caused by micellar media. 相似文献
7.
8.
Aurora Martín-Calero Juan H. Ayala Venerando González Ana M. Afonso 《Analytical and bioanalytical chemistry》2009,394(4):937-946
The beneficial effects of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF4) ionic liquid (IL) as mobile phase additive, desorption solvent, and memory effect suppressor in solid-phase microextraction (SPME)–high-performance liquid chromatography with fluorescence detection for the determination of six heterocyclic aromatic amines have been evaluated for the first time. Several chromatographic parameters have been evaluated in the presence or absence of IL or using triethylamine as the most common mobile phase additive, with a Nova-Pak® C18 stationary phase. This IL was found to be clearly superior to triethylamine for efficiency as well as peak shape enhancement and sensitivity increase. SPME was chosen because it is faster than conventional extraction techniques and allowed us to minimize the use of organic solvents. However, memory effect may become a problem when a high-sensitivity detector is used. The appropriate conditions for the desorption step and to eliminate the memory effect involving BMIm-BF4 were established and optimized. The method was applied for the determination of these compounds in commercial meat extracts. 相似文献
9.
Conde FJ Afonso AM González V Ayala JH 《Analytical and bioanalytical chemistry》2006,385(7):1162-1171
A sampling and analysis method for the determination of 21 phenolic compounds in smoke samples from biomass combustion has
been developed. The smoke is used to make smoked foods, following an artisanal procedure used in some parts of the Canary
Islands. The sampling system consists of a Bravo H air sampler, two impingers, each one containing an aqueous solution of
sodium hydroxide 0.1 mol L−1, followed by a silica gel trap. The variables optimized to reach the best sampling conditions were volume of absorbent solution
and sampling flow. Under the optimum conditions, 100 mL of absorbent solution of NaOH 0.10 mol L−1 and 2 L min−1 for the sampling flow, sampling efficiencies are higher than 80%. Analysis of phenolic compounds was carried out by headspace
solid-phase microextraction (HS-SPME) coupled to gas chromatography–mass spectrometry (GC-MS). Five different fiber coatings
were employed in this study. By means of a central composite design, extraction time, salt concentration, and pH of the solution
were optimized: 65-μm carbowax–divinylbenzene, extraction time 90 min, concentration in NaCl of 35% (m/v), and pH 2 yielded
the highest response. Detection limits of phenol and their alkyl derivatives, guaiacol and eugenol, are between 1.13 and 4.60 ng mL−1. 3-Methoxyphenol, 2,6-dimethoxyphenol, and vanillin have detection limits considerably higher. Good linearity (R
2≥0.98) was observed for all calibration curves in the established ranges. The reproducibility of the method (RSD, relative
standard deviation) was found to oscillate between 7 and 18% (generally close or lower than 10%). 相似文献
10.
Antonino Corsaro Ugo Chiacchio Venerando Pistarà Roberto Romeo Felicia D'Andrea Emanuele Attolino 《Tetrahedron》2004,60(17):3787-3795
Completely protected 4-deoxy-α-L-threo-hex-4-enopyranosides 1c,d undergo the dichlorocarbene addition affording exclusively diastereomeric adducts 5c,d with the cyclopropane ring anti to the C-3 alkyloxy substituent, while the reaction with 3-unprotected derivatives 1a,b affords a mixture of syn and anti derivatives. Under the Simmons-Smith cyclopropanation adducts 2a-d with a syn stereochemistry are obtained. Starting from 5b, the cyclopropanated sugar 3b is obtained by reduction with LiAlH4, thus the two diastereomers 2b and 3b can be stereoselectively obtained through the two different pathways. For a useful comparison, 4-deoxy-β-L-threo-hex-4-enopyranoside 1e was also subjected to the above two cyclopropanation methods affording the expected cycloadduct 2e and a diastereomeric mixture of dichlorocycloadducts 4e and 5e (4e/5e=2.8:1). 相似文献