Search results for "CAPILLARY ELECTROPHORESIS"
showing 10 items of 131 documents
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…
Improvement of the electrophoretic protein profiles of Leguminosae gums extracts using gamanase and application to the evaluation of carob–guar mixtu…
2004
Abstract A quantitative assay for guar gum in carob gum, based on the extraction of proteins in acetonitrile–water (7:3), separation by capillary electrophoresis and multiple linear regression (MLR) using the areas of nine selected peaks as predictors, was improved by performing the extraction in the presence of gamanase. In the absence of the enzyme, peak migration times and areas depended on the guar content, which complicated peak identification and evaluation. Manual correction of the migration times by comparison with standard electropherograms obtained with pure carob and carob–guar mixtures was required; however, when the proteins were extracted under sonication at 60 °C for 30 min i…
Determination of -Ascorbic Acid in Lycopersicon Fruits by Capillary Zone Electrophoresis
2001
This study shows an improved method for the determination of L-ascorbic acid (l-AA) in fruits of Lycopersicon by capillary zone electrophoresis (CZE). Two backgrounds electrolytes (BGEs) have been tested: (i) 400 mM borate at pH 8.0 and 1 x 10(-2)% hexadimethrine bromide, for the separation of Eulycopersicon subgenus species; and (ii) as in BGE(i) but supplemented with 20% (v/v) acetonitrile, for the separation of species of the Eriopersicon subgenus. The present procedures were compared with two routine methods-enzymatic assay and potentiometric titration with 2,6-dichlorophenol-indophenol. While these routine methods presented some difficulties in quantifying l-AA in several Lycopersicon …
Simultaneous quantification of the main organic acids and carbohydrates involved in tomato flavour using capillary zone electrophoresis
2002
A capillary zone electrophoresis (CZE) procedure for the simultaneous determination of the major organic acids (oxalate, malate and citrate) and carbohydrates (fructose, glucose and sucrose) in Lycopersicon fruits is reported. Comparison of this method with routine HPLC methods indicates that the CZE method offers several attractive features (speed, resolution, sensitivity and cost) which significantly improve the determination of these compounds. Detection limits were better than 1.6 µg ml−1 for organic acids and from 13 to 24 µg ml−1 for carbohydrates; repeatabilities were better than 2.1% for migration times and between 1.4 and 7.3% for peak areas. The proposed protocol is very useful to…
Capillary zone electrophoresis for the determination of thiabendazole, prochloraz and procymidone in grapes
2001
Capillary zone electrophoresis with UV detection was applied to the simultaneous determination of thiabendazole, prochloraz and procymidone in grapes. Electrolyte conditions such as pH, composition and concentration of the buffer, addition of organic solvent and working voltage were checked to obtain a high-performance separation of the three fungicides (by measurement of separation efficiency and resolution). The most critical parameter was the pH of the running buffer. The best separation was achieved in 4 mM phosphate solution at pH 3.5. The repeatability of the migration times, expressed as RSD, was <0.44%. The three peaks were completely resolved with a separation efficiency up to 100 …
Quantitative analysis of six pesticides in fruits by capillary electrophoresis-electrospray-mass spectrometry.
2005
A method to identify and quantify six pesticide residues - dinoseb, pirimicarb, procymidone, pyrifenox, pyrimethanil, and thiabendazole - in peaches and nectarines using capillary electrophoresis-electrospray ionization-quadrupole ion trap-tandem mass spectrometry (CE-ESI-MS/MS) is described. Separation was carried out using a buffer of 0.3 M ammonium acetate at pH 4 with 10% methanol. Pesticide residues present in peach and nectarine samples were preconcentrated by solid-phase extraction using C(18), eluted with CH(2)Cl(2), concentrated to dryness, and redissolved in buffer to obtain lower detection limits. The recoveries of the analytes ranged from 58 to 99% and the relative standard devi…
Analysis of thiabendazole and procymidone in fruits and vegetables by capillary electrophoresis–electrospray mass spectrometry
2002
Abstract A capillary electrophoresis–mass spectrometry method for determining procymidone and thiabendazole in apples, grapes, oranges, pears, strawberries and tomatoes is described. Separation is achieved using a buffer of formic acid–ammonium formate at pH 3.5 with 2% of methanol. Fungicide residues present in the sample are preconcentrated by both solid-phase extraction and injection of large sample volumes into the capillary by a stacking technique, to obtain lower detection limits. Ionization is performed at atmospheric pressure in an electrospray type source and detection is carried out using positive ionization and selected ion monitoring modes. The quantitation limits are 0.005 and …
Determination of glyphosate and aminomethylphosphonic acid in natural water using the capillary electrophoresis combined with enrichment step
2005
A previously elaborated capillary electrophoresis (CE) method used for the determination of glyphosate and aminomethylphosphonic acid (AMPA) was slightly modified in order to improve the sensitivity. However, detection limits attained (5 μg mL−1 for glyphosate and 4 μg mL−1 for AMPA) were still not satisfactory for analytical purposes, thus the addition of a preconcentration step before the CE analysis was proposed. AMBERLITE®IRA-900, a strong anion-exchange resin, was used to preconcentrate both analytes in environmental aqueous samples. The experimental conditions optimised in a previous work were readapted, by decreasing the eluent concentration due to CE limitations. Satisfactory result…
Resolution of overlapped non-absorbing and absorbing solutes using either an absorption null-balance detection window or multivariate deconvolution a…
2004
Abstract Non-absorbing alkyl ether sulfates (AES) can be separated using anthraquinone-2-carboxylic acid (AQCA) as a probe; however, absorbing alkyl benzene sulfonates (ABS), if present, interfere indirect detection of most AES oligomers. Overcoming of this interference, as well as the simultaneous characterisation and evaluation of AES, fatty acids and ABS, was accomplished by using a diode-array detector and the procedures here discussed. First, it was shown that ABS can be made undetectable by using a 9 nm wide and 227 nm centred charge-absorptivity null-balance detection window (NBDW), where its contribution to the absorbance cancels the dilution effects that its presence induces on the…
Separation and determination of homologues of linear alkylbenzenesulfonates by nonaqueous capillary zone electrophoresis using alkylammonium salts in…
2001
The separation of linear alkylbenzene sulfonates (LAS) by nonaqueous capillary electrophoresis (NACE) using negative polarity, and a buffer containing acetic acid and an alkylamine in nonaqueous ethanol, has been investigated. Several primary, secondary, and tertiary alkylamines with alkyl chains of different length were compared. The solutes travelled against the electroosmotic flow (EOF), and at the same time were braked by association with the alkylamine molecules or with the alkylammonium ions. The best resolution between adjacent LAS homologues (R approximately 2.1), partial isomer resolution in two peaks, and at the same time an excellent repeatability, was obtained with a small dipen…