Use of onion extract as a dairy cattle feed supplement: monitoring propyl propane thiosulfonate as a marker of its effect on milk attributes.

Posted on 28 February, 2017 by fqm302

Onion extract is used as a feed supplement for the diet of dairy cows, acting as inhibitor of methane production; however, its properties could alter sensory attributes of milk. In this work, we propose a method to evaluate the influence of this extract on milk properties, using propyl propane thiosulfonate (PTSO) as a marker. PTSO is extracted using a quick, easy, cheap, effective, rugged, and safe procedure and monitored by high-performance liquid chromatography with ultraviolet detection. The method was applied to milk samples obtained from 100 dairy cows fed during 2 months with enriched feed. In addition, a milk tasting panel was established to evaluate the PTSO residue that should not be exceeded to guarantee milk sensory attributes. It was established that a value of PTSO lower than 2 mg kg–1 does not alter milk organoleptic properties. This fact makes onion extract an interesting alternative as a feed supplement to control the methane emissions without any influence on milk attributes.

Posted in Animal feed, HPLC, PTSO, QuEChERS, UV-vis | Tagged , , | Comments Off on Use of onion extract as a dairy cattle feed supplement: monitoring propyl propane thiosulfonate as a marker of its effect on milk attributes.

High-throughput methodology for the determination of carbamates in food supplements by UHPLC–MS/MS.

Posted on 28 February, 2017 by fqm302

Food supplements are increasingly consumed products that claim to have several benefits for health. In many cases, these supplements contain herbal products and, as a consequence, can be contaminated with pesticides used in crops. This study aimed to use a QuEChERS-based method and ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) to determine carbamate residues in different food supplements, all of them containing different herbal products, such as Garcinia cambogia, Cynaras colymus, Equisetum arvense, soy lecithin, Spirulina maxima, Fucus vesiculosus, olive leaf and garlic extract. After testing different sorbents, the combination of PSA/C18 (75/25) provided the best clean-up effect. The method was validated in terms of linearity, matrix effect, limit of quantification, precision (intra and interday) and trueness. Good linearity (r2 > 0.99) and precision lower than 16% (expressed as relative standard deviation) were obtained in all cases. Moreover, the recovery in all studied samples was within the acceptable range (71–104%), and limit of quantification was 0.8 µg kg−1. The method was proved to be successful as a quantitative method for carbamate residue analysis in various food supplements, which are known to be complex matrices.

Posted in AGL2015-70708-R, Carbamates, Mass spectrometry, QuEChERS, Supplements, UHPLC | Tagged , , | Comments Off on High-throughput methodology for the determination of carbamates in food supplements by UHPLC–MS/MS.

Evaluation of a new modified QuEChERS method for the monitoring of carbamate residues in high-fat cheeses by using UHPLC–MS/MS.

Posted on 27 February, 2017 by fqm302

A simple and efficient method for the determination of 28 carbamates in high-fat cheeses is proposed. The methodology is based on a modified quick, easy, cheap, effective, rugged, and safe procedure as sample treatment using a new sorbent (Z-Sep+) followed by ultra-high performance liquid chromatography with tandem mass spectrometry determination. The method has been validated in different kinds of cheese (Gorgonzola, Roquefort, and Camembert), achieving recoveries of 70–115%, relative standard deviations lower than 13% and limits of quantification lower than 5.4 μg/kg, below the maximum residue levels tolerated for these compounds by the European legislation. The matrix effect was lower than ±30% for all the studied pesticides. The combination of ultra-high performance liquid chromatography and tandem mass spectrometry with this modified quick, easy, cheap, effective, rugged, and safe procedure using Z-Sep+ allowed a high sample throughput and an efficient cleaning of extracts for the control of these residues in cheeses with a high fat content.

Posted in Carbamates, Cheese, Mass spectrometry, P12-AGR-1647, QuEChERS, UHPLC | Tagged , , | Comments Off on Evaluation of a new modified QuEChERS method for the monitoring of carbamate residues in high-fat cheeses by using UHPLC–MS/MS.

Development of magnetic molecularly imprinted polymers for selective extraction: determination of citrinin in rice samples by liquid chromatography with UV diode array detection.

Posted on 23 January, 2017 by fqm302

In this work, we report the synthesis of novel magnetic molecularly imprinted polymers (m-MIPs) and their application to the selective extraction of the mycotoxin citrinin (CIT) from food samples. The polymers were prepared by surface imprinting of Fe3O4 nanoparticles, using 2-naphtholic acid (2-NA) as template molecule, N-3,5-bis(trifluoromethyl)phenyl-N‘-4-vinylphenyl urea and methacrylamide as functional monomers and ethyleneglycol dimethacrylate as cross-linker. The resulting material was characterized by transmission electron microscopy (TEM), and X-ray diffraction (XRD) and Fourier transform infrared spectroscopies (FT-IR). The polymers were used to develop a solid-phase extraction method (m-MISPE) for the selective recovery of CIT from rice extracts prior to its determination by HPLC with UV diode array detection. The method involves ultrasound-assisted extraction of the mycotoxin from rice samples with (7:3, v/v) methanol/water, followed by sample cleanup and preconcentration with m-MIP. The extraction (washing and elution) conditions were optimized and their optimal values found to provide CIT recoveries of 94–98 % with relative standard deviations (RSD) less than 3.4 % (n = 3) for preconcentrated sample extracts (5 mL) fortified with the analyte at concentrations over the range 25–100 μg kg−1. Based on the results, the application of the m-MIPs facilitates the accurate and efficient determination of CIT in rice extracts.

Posted in HPLC, MIPs, Mycotoxins, Rice, UV-vis | Comments Off on Development of magnetic molecularly imprinted polymers for selective extraction: determination of citrinin in rice samples by liquid chromatography with UV diode array detection.

Metodologías avanzadas para la determinación de 5-nitroimidazoles en muestras alimentarias, ambientales y clínicas.

Posted on 16 January, 2017 by fqm302

The goals of this Thesis are within the scopes of several research projects carried out in the last years and included within the research lines of the group in which this Thesis has been
performed.

The main goal has been the development of novel, sensitive and selective analytical methods for the determination of several drugs belonging to the antibiotic family called 5-nitroimidazoles (5-NDZs). These compounds are prescribed in human medicine but their use in veterinary medicine is forbidden in the European Union. However, their use is allowed in other countries, so the control of their residues in food is a requirement in order to guarantee that current legislation is enforced. For such a reason, in this Thesis, several methods have been developed for the determination of 5-NDZ residues, including their metabolites, and which are suitable for their application in drug monitoring in biological fluids, food safety and residue determination in environmental field. Miniaturized techniques such as capillary electrophoresis (CE), capillary electrochromatography (CEC), and capillary liquid chromatography (CLC), as well as a high efficiency technique such as ultra-high performance liquid chromatography (UHPLC), have been selected for accomplishing this purpose. These techniques have been coupled to different detection techniques such as ultraviolet-visible (UV-Vis) spectrophotometry and tandem mass spectrometry (MS/MS). Furthermore, both on-line preconcentration (in the case of CE) and off-line preconcentration methods have been proposed, allowing sensitivity enhancement. Moreover, they result in new, more efficiency and environmental-friendly sample treatments for the analysis of 5-NDZ residues, according to the current trends in Green Chemistry.

The following specific goals of this Thesis must be remarked:

  1. Determination of 5-NDZs by CE-UV in environmental water samples and food products of animal origin, considering both off-line and on-line preconcentration techniques for overcoming the lack of sensitivity attributed to CE-UV.
  2. Demonstration of the potential of CE-MS/MS hyphenation for the control of
    5-NDZ residues in biological fluids, considering the identification capacity of the
    selected detection.
  3. Proposal of an efficiency procedure for packing capillaries for their further
    application in CEC and consequently, evaluation of the potential of this technique
    coupled to UV detection for the determination of 5-NDZs.
  4. Evaluation of CEC-MS hyphenation for the therapeutic monitoring of these drugs
    (research carried out in the group of Dr. Salvatore Fanali during a predoctoral stay
    in the ‘Istituto di Metodologie Chimiche (IMC) of Consiglio Nazionale delle Ricerche di
    Montelibretti’, Rome, Italy).
  5. Use of CLC for the determination of 5-NDZs in food products as alternative to
    traditional HPLC.
  6. Investigation of the advantages of UHPLC coupled to both UV and MS/MS
    detection, for the quick quantification of 5-NDZ residues in products of animal
    origin intended to human consumption.
  7. Proposal of new, simple, quick, selected and environmental-friendly simple treated
    for the determination of 5-NDZs, including their metabolites, as alternative to the
    methods that have been previously reported. Evaluation of these simple
    treatments in different matrices with the aim of demonstrating their suitability in
    terms of selectivity and sensitivity.
Posted in Theses | Comments Off on Metodologías avanzadas para la determinación de 5-nitroimidazoles en muestras alimentarias, ambientales y clínicas.

Determination of aflatoxins in yogurt by dispersive liquid – liquid microextraction and HPLC with photo-induced fluorescence detection.

Posted on 16 January, 2017 by fqm302

A high-performance liquid chromatography (HPLC) method with fluorescence detection for the determination of aflatoxins B1, B2, G1, G2, and M1 in yogurt using dispersive liquid–liquid microextraction as alternative sample treatment has been developed. To enhance the fluorescence of aflatoxins B1 and G1, a post-column photochemical derivatization has been proposed, avoiding the use of derivatization reagents. The method was validated using natural yogurt as representative matrix, showing a good linearity in the studied range (25–500 ng kg−1) and limits of quantification below the maximum level established by European Union in milk for the manufacture of milk-based products. Satisfactory recoveries ranging from 69.4 to 99.7 %, with relative standard deviations lower than 11.2 %, were obtained for all the compounds. The proposed method is simple, rapid, with low solvent consumption, inexpensive, and environmentally friendly.

Posted in AGL2015-70708-R, Aflatoxins, DLLME, HPLC, P12-AGR-1647, Photo-induced, Yogurt | Tagged , | Comments Off on Determination of aflatoxins in yogurt by dispersive liquid – liquid microextraction and HPLC with photo-induced fluorescence detection.

Salting-out assisted liquid–liquid extraction coupled to ultra-high performance liquid chromatography–tandem mass spectrometry for the determination of tetracycline residues in infant foods

Posted on 13 December, 2016 by fqm302

The use of salting-out assisted liquid–liquid extraction (SALLE) combined with ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) has been evaluated for the determination of tetracyclines in infant foods based on meat and vegetables or in milk. To obtain satisfactory extraction efficiencies for the studied analytes, several parameters affecting the SALLE procedure were optimized. Analytical performances of the method were satisfactory, obtaining limits of quantification lower than 0.48 μg kg−1 in all cases. The precision, expressed as relative standard deviation (%, RSD) was below 11.3%. The extraction efficiency for fortified samples ranged from 89.2 to 96.8%, with RSDs lower than 7.3%. Matrix effect was evaluated for all samples studied, being lower than |21|% in all cases. In relation to the low solvent consumption, the proposed methodology could be considered rapid, cheap and environmentally friendly. Its applicability has been successfully tested in a wide range of infant foods.

Posted in Infant foods, Mass spectrometry, P12-AGR-1647, SALLE, Tetracyclines, UHPLC | Tagged | Comments Off on Salting-out assisted liquid–liquid extraction coupled to ultra-high performance liquid chromatography–tandem mass spectrometry for the determination of tetracycline residues in infant foods

Capillary electrophoresis-tandem mass spectrometry combined with molecularly imprinted solid phase extraction as useful tool for the monitoring of 5-nitroimidazoles and their metabolites in urine samples

Posted on 24 November, 2016 by fqm302

A novel capillary electrophoresis-tandem mass spectrometry approach is proposed for the determination of eleven 5-nitroimidazoles in urine samples for therapeutical drug monitoring purposes. A comparison between two separation modes, namely micellar electrokinetic chromatography and capillary zone electrophoresis was carried out, obtaining higher selectivity when 1 M formic acid (pH 1.8) was selected as background electrolyte. 5-Nitroimidazoles were hydrodynamically injected in water for 40 s at 50 mbar and their separation was performed at 28 kV and 25 °C. To improve migration time repeatability, a pressure of 50 mbar was applied to the inlet vial during runs without any loss of peak resolution. Electrospray ionization parameters were established as follow: 6 L/min, dry gas flow rate; 51,021.2 Pa, nebulization pressure; 160 °C, dry gas temperature. Sheath liquid consisted of a mixture of propan-2-ol/water/acetic acid (60.0:38.8:0.2% v/v/v) supplied at 3.3 µL/min. MS parameters were optimized for analyte identification through their MS2 and MS3 spectra. The method was applied to the determination of 5-nitroimidazoles in urine samples, applying molecularly imprinted solid phase extraction for sample clean-up. Recoveries higher than 79.2% demonstrated the suitability of the procedure. Limits of detection ranged from 9.6 to 130.2 µg/L while precision assays resulted in relative standard deviations for peak areas lower than 16.1%.

Posted in 5-nitroimidazoles, CZE, MEKC, MIPs, Mass spectrometry, P12-AGR-1647, Urine | Comments Off on Capillary electrophoresis-tandem mass spectrometry combined with molecularly imprinted solid phase extraction as useful tool for the monitoring of 5-nitroimidazoles and their metabolites in urine samples

QuEChERS-based method for the determination of carbamate residues in aromatic herbs by UHPLC-MS/MS

Posted on 16 September, 2016 by fqm302

A new reliable, fast and highly sensitive method based on ultra-high performance liquid chromatography tandem mass spectrometry has been developed and validated for the determination of 28 carbamates in aromatic herbs. A modified QuEChERS-based method was optimized for the extraction of carbamate residues from a wide variety of fresh herbal products. The proposed method allowed recoveries higher than 72%, achieving quantification limits of 2 μg kg−1, therefore below maximum residue limits established for this type of samples. The combination of QuEChERS with UHPLC-MS/MS introduces a high-throughput methodology for the monitoring of these residues in this type of matrices scarcely explored. The analysis of the real samples revealed that several samples sold in the European Union and in the North West region of Cameroon contain pesticides in concentrations below the maximum residue limits.

Posted in AGL2015-70708-R, Aromatic herbs, Carbamates, Mass spectrometry, QuEChERS, UHPLC | Tagged | Comments Off on QuEChERS-based method for the determination of carbamate residues in aromatic herbs by UHPLC-MS/MS

Capillary electrochromatography coupled with dispersive liquid-liquid microextraction for the analysis of benzimidazole residues in water samples

Posted on 12 August, 2016 by fqm302

A novel method for the analysis of benzimidazole residues in water samples by capillary electrochromatography-UV detection (290 nm), using laboratory-made packed columns is presented. Capillaries (25 cm packed length×75 µm inner diameter, 34 cm total length, 25.5 cm effective capillary length) were packed with C18 particles (5 µm, non-encapped) following a high pressure packing procedure and using a compact steel unit designed for packing capillary columns. Acetone was employed as solvent to carry the particles through the capillary and pack it under a pressure of 42 MPa. Outlet and inlet frits were made by sintering the particles of the stationary phase by heating the packed material with a nichrome ribbon connected to a 7 V AC power supply. With the aim of achieving a good analytical performance, the variables that affected the separation were studied, using a mobile phase composition of 60:40 (v/v) acetonitrile/water containing ammonium acetate (1 mM, pH 6.5), a separation voltage of 25 kV and a temperature of 25 °C. In addition, a combined hydrodynamic-electrokinetic injection mode was considered and samples were injected for 75 s under a voltage of 12.5 kV and a pressure of 11.5 bar. Finally, the determination of benzimidazoles in water samples was accomplished by capillary electrochromatography using dispersive liquid-liquid microextraction as sample treatment. Variables affecting the extraction efficiency were optimized, using chloroform and ethanol as extraction and disperser solvents, respectively.

This method was applied to different water samples, obtaining satisfactory results in terms of linearity (R2≥0.990), repeatability (RSD≤1.2%), reproducibility (RSD≤2.2%) and trueness (R≥87.7%). Detection and quantification limits were lower than 2.8 µg L−1 and 9.3 µg L−1, respectively.

Posted in Anthelmintic, Benzimidazoles, DLLME, Electrochromatography, P12-AGR-1647, Projects, UV-vis, Water | Tagged , | Comments Off on Capillary electrochromatography coupled with dispersive liquid-liquid microextraction for the analysis of benzimidazole residues in water samples