Search results for "CAPI"
showing 10 items of 2622 documents
Direct determination of oleic acid in soybean oil by capacitively coupled contactless conductivity detection capillary electrophoresis in an oil-misc…
2014
Este trabalho teve por objetivo desenvolver um método analítico direto e rápido para a determinação de ácido oleico em óleo de soja por eletroforese capilar com detecção condutométrica sem contato. O eletrólito de corrida empregado foi uma mistura metanol/1-propanol (1:6 v/v) contendo 4 × 10-2 mol L-1 de KOH e 10% (v/v) em etileno glicol. As amostras foram preparadas pela solubilização de 50 g L-1 de óleo de soja e 1,33 × 10-3 de ácido salicílico (padrão interno) no eletrólito de corrida. Os ensaios quantitativos foram realizados adicionando ácido oleico puro às amostras, na faixa entre 0,53 e 2,13 × 10-3 mol L-1. Sob polaridade negativa, os solutos aniônicos deslocaram-se mais rapidamente …
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 …
Cylindrical optical microcavities: Basic properties and sensor applications
2011
Abstract A detailed theoretical analysis of the basic properties of whispering-gallery modes (WGM) of thin capillaries is presented. The sensitivity of the resonances, as well as the Q factor is analyzed as a function of the structural parameters of the capillary and the refractive index inside the capillary. A practical application where thin capillaries are used for the measurement of glucose concentration in water is presented as a chemical sensor demonstrator. A best sensitivity of 1.24 nm/% of glucose concentration in water is reported, which corresponds to more than 850 nm/RIU. Additionally, different experimental approaches are discussed to improve the sensitivity and the detection l…
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…
Selective and sentivive method based on capillary liquid chromatography with in-tube solid phase microextraction for determination of monochloramine …
2015
Abstract Due to the difficulties of working with chloramines, a critical examination of monochloramine standard preparation has been performed in order to select the best synthesis conditions. The analyte has been determined by in-tube solid phase extraction coupled to capillary liquid chromatography with UV detection (IT-SPME Capillary LC DAD). Potential factors affecting the response of monochloramine such as the pH of mobile phase and the volume of sample processed by IT-SPME Capillary LC DAD have been investigated and optimized. According to the results of the study, 0.1 mL or 4.0 mL of sample at neutral pH were loaded in the chromatographic system. A sensitive and selective method has …
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 …
Use of gold nanoparticle-coated sorbent materials for the selective preconcentration of sulfonylurea herbicides in water samples and determination by…
2012
Abstract Two new gold nanoparticle (NP) coated materials (silica supported on gold NP with and without ionic liquid) were synthesized for solid phase extraction of sulfonylurea herbicides (SUHs), such as bensulfuron-methyl (BSM), metsulfuron-methyl (MSM), pyrazosulfuron-methyl (PSM), thifensulfuron-methyl (TFM) and triasulfuron (TS), from water samples, followed by capillary liquid chromatography coupled to diode array detection (CLC–DAD). Several factors influencing the preconcentration efficiency of SUHs and its subsequent determination, such as pH of the sample, eluent and reusability of sorbents, have been investigated. Under the optimum conditions, the developed method allowed the dete…
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…