Trace determination of sulfonylurea herbicides in water and grape samples by capillary zone electrophoresis using large volume sample stacking

Posted on 23 May, 2010 by fqm302

A sensitive and reliable method using capillary zone electrophoresis with UV-diode array detection has been developed and validated for trace determination of residues of sulfonylurea herbicides in environmental water samples and grapes from different origins. The analytes included are triasulfuron, rimsulfuron, flazasulfuron, metsulfuron-methyl, and chlorsulfuron. Optimum separation has been achieved on a 48.5-cm × 50-μm (effective length 40 cm) bubble cell capillary using 90 mM ammonium acetate buffer, pH 4.8, by applying a voltage of 20 kV at 25 °C and using p-aminobenzoic acid as the internal standard. In order to increase sensitivity, large volume sample stacking with polarity switching has been applied as on-line preconcentration methodology. For water samples, a solid-phase extraction (SPE) procedure based on the use of Oasis HLB cartridges was applied for off-line preconcentration and cleanup. For grape samples, the SPE procedure was achieved with C18 sorbent, after extraction of the compounds with MeOH:H2O (1:1) by sonication. The limits of detection for the studied compounds were between 0.04 and 0.12 μg/L for water samples and 0.97 and 8.30 μg/kg in the case of grape samples, lower in all cases than the maximum residue limits permitted by the EU for this kind of food. The developed methodology has demonstrated its suitability for the monitoring of these residues in environmental water and grape samples with high sensitivity, precision, and satisfactory recoveries.

Posted in CZE, Electrophoresis, Food, Fruit, Pesticides, Stacking, Sulfonylurea, UV-vis, Water | Tagged | Comments Off on Trace determination of sulfonylurea herbicides in water and grape samples by capillary zone electrophoresis using large volume sample stacking

Advances in chemiluminescence detection in HPLC and capillary electrophoresis

Posted on 23 April, 2010 by fqm302

During the last two decades, the use of chemiluminescence (CL) in liquid phase has provided a well-established and widely applied spectrometric branch of Analytical Chemistry. The versatility of this technique permits the determination of a great variety of species that can participate in a given CL reaction, such as CL precursors, oxidants, catalysts, inhibitors or derivatized molecules, the CL emission being proportional to the concentration of these substances. Due to its simplicity, low cost and its often high  sensitivity and selectivity, CL-based emission has become a useful detecting tool in flow injection, high performance liquid chromatography (HPLC) and capillary electrophoresis (CE).

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Laser induced fluorescence coupled to capillary electrophoresis for the determination of fluoroquinolones in foods of animal origin using molecularly imprinted polymers

Posted on 17 February, 2010 by fqm302

A method for the simultaneous determination of four fluoroquinolones of veterinary use (ciprofloxacin, danofloxacin, enrofloxacin and sarafloxacin) in two complex matrixes, such as bovine raw milk and pig kidney, has been established and validated. The method is based on the use of capillary electrophoresis (CE) coupled with a very sensitive detection mode, such as laser induced fluorescence (LIF) detection, due to the fact the all the compounds selected show native fluorescence. In order to achieve high selectivity in the sample treatment procedure, a commercially available molecularly imprinted polymer has been used for the solid phase extraction of the analytes. Once the retention and elution processes were optimized, the final extract was analyzed by CE-LIF using a 325 nm He–Cd laser. Optimum separation was obtained in a 70 cm × 75 μm capillary using a 125 mM phosphoric acid solution at pH 2.8 with 36% methanol as background electrolyte. The method provided very low detection limits, ranging from 0.17 to 0.98 μg/kg for milk and 1.10 to 10.5 μg/kg for kidney, with acceptable precision and satisfactory recoveries.

Posted in Antibiotics, CZE, Electrophoresis, Fluorescence, Food, LIF, MIPs, Milk, Pig kidney, Quinolones, Sample treatment | Tagged | Comments Off on Laser induced fluorescence coupled to capillary electrophoresis for the determination of fluoroquinolones in foods of animal origin using molecularly imprinted polymers

Sensitive determination of fluoroquinolone residues in waters by capillary electrophoresis with laser induced fluorescence detection

Posted on 9 February, 2010 by fqm302

A sensitive capillary electrophoresis –laser-induced fluorescence method has been developed for the determination of six fluoroquinolones of human (ofloxacin, lomefloxacin, and norfloxacin) and veterinary use (danofloxacin, enrofloxacin, and sarafloxacin) in different kinds of water. Fluorescence detection was achieved using a He-Cd laser, with a wavelength of 325 nm. Separation was performed in a fused-silica capillary, and conditions were optimized to obtain the most adequate separation and with the best sensitivity. The separation was carried out in a 70-cm-long capillary (75 μm internal diameter, effective length 55 cm) by using a 125 mM phosphoric acid separation buffer at pH 2.8, with 36% of methanol. The water sample pretreatment involved the separation and preconcentration of the analytes by solid phase extraction. Two reverse-phase cartridges have been evaluated, namely Oasis hydrophilic–liphophilic balance and Strata-X; the latter provided the best recoveries for the selected analytes. The method shows very low detection limits (0.3–1.9 ng/L) with acceptable recoveries and precisions and has been successfully applied to the analysis of well and tap water samples

Posted in Antibiotics, CZE, Electrophoresis, Fluorescence, LIF, Quinolones, SPE, Water | Tagged | Comments Off on Sensitive determination of fluoroquinolone residues in waters by capillary electrophoresis with laser induced fluorescence detection

Peroxyoxalate photoinduced chemiluminescence detection of norfloxacin in pharmaceutical products by flow injection analysis

Posted on 28 January, 2010 by fqm302

A new method for the determination of norfloxacin by flow injection analysis based on photoinduced chemiluminescence detection is proposed. We have selected the peroxyoxalate (PO) reaction based on the possibility of detecting fluorescent products derived from a photochemically induced decomposition of norfloxacin, observing high signal when the derivative participates in the reaction. A FIA device, with two-injection valves for the introduction of both the PO and the photodecomposed analyte solutions in the flow system, has been used, avoiding the problems arising from the use of organic solvents. The method was applied to the monitoring of norfloxacin in pharmaceuticals.

Posted in Antibiotics, Chemiluminescence, Drugs, Flow injection analysis, Photoinduced, Quinolones | Tagged , | Comments Off on Peroxyoxalate photoinduced chemiluminescence detection of norfloxacin in pharmaceutical products by flow injection analysis