Comparison of different sample treatments for the analysis of quinolones in milk by capillary-liquid chromatography with laser induced fluorescence detection

Posted on 5 July, 2011 by fqm302

A simple and very sensitive capillary-liquid chromatography method coupled with laser induced fluorescence detection has been developed for the simultaneous determination of seven quinolones of veterinary use in milk. Moreover, a comparison between two different sample treatments (QuEChERS and molecularly imprinted polymer, MIP) has been carried out in terms of efficiency of the extraction (number of analytes to be analysed and absence of interferences), throughput, linear dynamic range in matrix-matches calibrations, detection and quantification limits and accuracy (trueness and precision, by means of recovery assays). The results showed that the QuEChERS procedure was more efficient and faster, showing good recoveries, sensitivity and precision for all the studied compounds. Employing this proposed method, very low detection limits, between 0.4 μg/kg for danofloxacin, and 6 μg/kg for sarafloxacin, have been obtained.

Posted in Capillary HPLC, LIF, MIPs, Milk, QuEChERS, Quinolones | Tagged | Comments Off on Comparison of different sample treatments for the analysis of quinolones in milk by capillary-liquid chromatography with laser induced fluorescence detection

Use of dispersive liquid–liquid microextraction for the determination of carbamates in juice samples by sweeping-micellar electrokinetic chromatography

Posted on 25 April, 2011 by fqm302

Dispersive liquid–liquid microextraction (DLLME) has been proposed for the extraction and preconcentration of 12 carbamate pesticides in juice samples, followed by their determination by micellar electrokinetic chromatography with diode-array detection. To improve sensitivity, an on-capillary sample concentration method based on sweeping has been developed. Also, separations were performed in an extended light path fused-silica capillary; the separation buffer consisted of 100 mM borate and 50 mM SDS (pH 9.0) with 5% acetonitrile. Samples were introduced by hydrodynamic injection, dissolved in the separation buffer, but free of micelles. Several parameters of the DLLME procedure (such as type and volume of extraction and dispersive solvents, pH, salt addition, and extraction time) were optimized. Recoveries obtained for fortified juice samples (banana, pineapple, and tomato) at three different concentration levels, ranged from 78% to 105%, with relative standard deviations lower than 9%. The limits of detection ranged from 1 to  7 μg l−1. Moreover, the method is fast, simple, and environmentally friendly.

Posted in Carbamates, DLLME, Electrophoresis, Juice, MEKC, Stacking, UV-vis | Tagged | Comments Off on Use of dispersive liquid–liquid microextraction for the determination of carbamates in juice samples by sweeping-micellar electrokinetic chromatography

Analytical applications of photoinduced chemiluminescence in flow systems—A review

Posted on 15 September, 2010 by fqm302

In this review, the recent evolution and the state of the art of photochemical reactions coupled with chemiluminescence processes are presented. Different chemiluminescence systems have been considered together with suitable photochemical derivatization processes that can affect either the analyte of interest or even the chemiluminogenic reagent, producing some derivatives able to participate more efficiently in the CL reactions and enhancing the CL emission. The on-line integration of the photochemical reactions as well as the coupling of this resulting photoinduced chemiluminescence (PICL) method with dynamic analytical systems, such as flow injection analysis, liquid or gas chromatography and capillary electrophoresis, have been discussed. Important applications of PICL have been proposed in environmental, pharmaceutical and food analysis.

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Determination of Ocratoxin A by capillary HPLC with laser induced fluorescence detection

Posted on 6 July, 2010 by fqm302

In this abstract we propose the coupling of capillary-HPLC with LIF for the analysis of OTA, using anionic micellar medium in the mobile phase, which constitutes a very efficient alternative, increasing sensitivity and selectivity. To the best of our knowledge, this is the first time that this methodology is used for OTA detection.

Posted in Capillary HPLC, Chromatography, Fluorescence, LIF, Mycotoxins | Tagged | Comments Off on Determination of Ocratoxin A by capillary HPLC with laser induced fluorescence detection

On-line preconcentration for the determination of aflatoxins in rice samples by micellar electrokinetic capillary chromatography with laser induced fluorescence detection

Posted on 30 June, 2010 by fqm302

MEKC coupling with LIF detection has been used for the determination of four aflatoxins (B1, B2, G1 and G2). Separations were performed in an uncoated fused-silica capillary (70 cm×75 μm id, 55 cm effective length), using 20 mM borate buffer with 30 mM SDS (pH 8.5) and 7% ACN. In order to increase sensitivity, an on-line preconcentration procedure was applied, based on sweeping, using the same separation buffer without SDS as solvent of the sample. The precision of the method was evaluated in terms of repeatability and intermediate precision and the results were acceptable in all cases (RSD<12%). With the on-line preconcentration LODs (obtained as 3×S/N) were as low as 0.11, 0.52, 0.04 and 0.10 μg/L for G2, G1, B2 and B1, respectively. Recovery studies were developed with extracts of rice samples spiked with aflatoxins, being in the range between 93.0 and 105.4%. The method has also been applied to the determination of aflatoxins in rice samples, and the results compared with those obtained by a standard method, being in good agreement.

Posted in Fluorescence, LIF, MEKC, Mycotoxins, Rice, Stacking | Tagged | Comments Off on On-line preconcentration for the determination of aflatoxins in rice samples by micellar electrokinetic capillary chromatography with laser induced fluorescence detection

Advances and analytical applications in chemiluminescence coupled to capillary electrophoresis

Posted on 18 June, 2010 by fqm302

The present review presents the state of the art of the developments, key strategies and analytical applications of chemiluminescence detection coupled to CE (CE-CL). Different parts considering the most common CL systems have been included, such as the tris(2,2′-bipyridine)ruthenium(II) system, the luminol and derivatives reaction, the peroxyoxalate CL or direct oxidations. New advances in homemade configurations and applications in different fields such as clinical, pharmaceutical, environmental and food analysis have been included. The focus is on studies which appeared from 2000 to the end of 2009.

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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