The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Miguel Valcarcel - One of the best experts on this subject based on the ideXlab platform.
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Liquid Chromatographic determination of natural and synthetic colorants in lyophilized foods using an automatic solid phase extraction system
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Monica Gonzalez, Mercedes Gallego, Miguel ValcarcelAbstract:Five synthetic and five natural colorants were determined in lyophilized dairy products and fatty foods using an automatic method based on lixiviation and a solid-phase extraction process that includes cotton and RP-C18 columns for the sequential retention of synthetic colorants and natural colorants, respectively. The lyophilization of the sample coupled with the separation procedure provides clean extracts despite the complexity of the matrices studied. In addition, the lyophilization process preserves the sample for at least 2 months without changes in the concentrations of the colorants. Identification and determination of synthetic and natural colorants were carried out using a Liquid Chromatograph equipped with a diode array detector. The detection limits achieved for all of the colorants (0.03−75 μg/g of lyophilized sample) allowed their determination within the limits established by the European Union, with good precision (≈4.5%). In addition, colorants spiked to different foods provided average r...
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automatic determination of n methylcarbamate pesticides by using a Liquid Liquid extractor derivatization module coupled on line to a gas Chromatograph equipped with a flame ionization detector
Journal of Chromatography A, 1993Co-Authors: Evaristo Ballesteros, Mercedes Gallego, Miguel ValcarcelAbstract:Abstract A continuous extraction system for the continuous introduction of carbamate pesticide derivatives into a gas-Liquid Chromatograph was developed. The hydrolysis products of aryl N-methylcarbamates (phenols) were extracted with or without derivatization in a continuous fashion by using ethyl acetate or acetic anhydride in n-hexane, respectively. The acetylated phenolic portion of N-methylcarbamates is highly selective, which was taken advantage of to identify six pesticides (propoxur, carbofuran, carbaryl, aminocarb, benthiocarb and methiocarb). The Chromatographic responses obtained were linear between 0.2 and 160 mg/l of the different N-methylcarbamates, and the relative standard deviation was 1.9–3.9%.
M Luque D De Castro - One of the best experts on this subject based on the ideXlab platform.
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anthocyanidins proanthocyanidins and anthocyanins profiling in wine lees by solid phase extraction Liquid Chromatography coupled to electrospray ionization tandem mass spectrometry with data dependent methods
Journal of Agricultural and Food Chemistry, 2013Co-Authors: M Delgado P De La Torre, C Ferreirovera, Feliciano Priegocapote, M Luque D De CastroAbstract:A method has been developed to study the content of anthocyanidins, proanthocyanidicins, and anthocyanins in wine lees, an abundant byproduct from wineries. Detection/quantitation of the target compounds was carried out by a hyphenated system consisting of a solid-phase extraction workstation (Prospekt-2 unit) online coupled to a Liquid Chromatograph-triple-quadrupole tandem mass spectrometer (LC-MS/MS), where standards were used for identification/quantitation of both anthocyanidins and proanthocyanidins. Owing to the lack of anthocyanins standards, advantages from the use of data-dependent methods were taken for their identification and confirmatory analysis. Combination of the scanning methods (viz. product-ion, precursor-ion, and neutral-loss scanning) allowed identifying five different anthocyanins present in wine residues. The results thus obtained have been validated by complementary analysis of the extracts using LC-TOF/MS in high-resolution mode. Quantitation of the monitored compounds was supported on selected reaction monitoring (SRM) and calibration curves run with standards of anthocyanidins and proanthocyanidins.
Samuel R. Gratz - One of the best experts on this subject based on the ideXlab platform.
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analysis of undeclared synthetic phosphodiesterase 5 inhibitors in dietary supplements and herbal matrices by lc esi ms and lc uv
Journal of Pharmaceutical and Biomedical Analysis, 2004Co-Authors: Samuel R. Gratz, Cheryl L Flurer, Karen A WolnikAbstract:A Liquid Chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method was developed to screen for the presence of synthetic phosphodiesterase type 5 (PDE-5) inhibitors including sildenafil, tadalafil and vardenafil. The method was applied to the analysis of dietary supplements and bulk herbal materials. Bulk powders or composites of tablets, capsules or Liquids were prepared and an extraction of PDE-5 inhibitors was performed using a mixture of acetonitrile and water with sonication. Identification of sildenafil, vardenafil or tadalafil was accomplished using a single quadrupole mass spectrometer coupled to a Liquid Chromatograph with an electrospray interface. Positive ion detection in the full scan mode was used while in-source collision induced dissociation (CID) provided several structurally significant fragment ions to aid in the mass spectral identification. Approximately half of the 40 botanical products analyzed were found to contain undeclared synthetic PDE-5 inhibitors. For products found to contain one of these three compounds by LC-MS, HPLC with UV detection was used for quantitation.
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identification and determination of carisoprodol in tablets by Liquid Chromatography mass spectrometry
2004Co-Authors: Angela S. Mohrhaus, Samuel R. GratzAbstract:A method for the identification and determination of carisoprodol in tablet dosage form is described. Tablets were ground and carisoprodol was extracted using acetonitrile with sonication. Extracts were filtered and further dilutions were made with water. The identification of carisoprodol was accomplished using a single quadrapole mass spectrometer coupled to a Liquid Chromatograph with an electrospray source and positive ion detection. For determining the carisoprodol content, selected ion monitoring of the molecular ion was used. A 5 :m 2.1 x 150 mm Zorbax SB-C18 column and a mobile phase of 35 % acetonitrile (0.1 % formic acid) and 65 % water (0.1 % formic acid) at a flow rate of 0.4 mL/minute provided adequate retention. The calibration curve generated during this analysis was linear between 0.5 and 40 :g/mL for carisoprodol with a correlation coefficient, r $ 0.9996. Spikes of tablets gave an average recovery of 93 % for carisoprodol.
Mercedes Gallego - One of the best experts on this subject based on the ideXlab platform.
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Liquid Chromatographic determination of natural and synthetic colorants in lyophilized foods using an automatic solid phase extraction system
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Monica Gonzalez, Mercedes Gallego, Miguel ValcarcelAbstract:Five synthetic and five natural colorants were determined in lyophilized dairy products and fatty foods using an automatic method based on lixiviation and a solid-phase extraction process that includes cotton and RP-C18 columns for the sequential retention of synthetic colorants and natural colorants, respectively. The lyophilization of the sample coupled with the separation procedure provides clean extracts despite the complexity of the matrices studied. In addition, the lyophilization process preserves the sample for at least 2 months without changes in the concentrations of the colorants. Identification and determination of synthetic and natural colorants were carried out using a Liquid Chromatograph equipped with a diode array detector. The detection limits achieved for all of the colorants (0.03−75 μg/g of lyophilized sample) allowed their determination within the limits established by the European Union, with good precision (≈4.5%). In addition, colorants spiked to different foods provided average r...
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automatic determination of n methylcarbamate pesticides by using a Liquid Liquid extractor derivatization module coupled on line to a gas Chromatograph equipped with a flame ionization detector
Journal of Chromatography A, 1993Co-Authors: Evaristo Ballesteros, Mercedes Gallego, Miguel ValcarcelAbstract:Abstract A continuous extraction system for the continuous introduction of carbamate pesticide derivatives into a gas-Liquid Chromatograph was developed. The hydrolysis products of aryl N-methylcarbamates (phenols) were extracted with or without derivatization in a continuous fashion by using ethyl acetate or acetic anhydride in n-hexane, respectively. The acetylated phenolic portion of N-methylcarbamates is highly selective, which was taken advantage of to identify six pesticides (propoxur, carbofuran, carbaryl, aminocarb, benthiocarb and methiocarb). The Chromatographic responses obtained were linear between 0.2 and 160 mg/l of the different N-methylcarbamates, and the relative standard deviation was 1.9–3.9%.
Karen A Wolnik - One of the best experts on this subject based on the ideXlab platform.
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analysis of undeclared synthetic phosphodiesterase 5 inhibitors in dietary supplements and herbal matrices by lc esi ms and lc uv
Journal of Pharmaceutical and Biomedical Analysis, 2004Co-Authors: Samuel R. Gratz, Cheryl L Flurer, Karen A WolnikAbstract:A Liquid Chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method was developed to screen for the presence of synthetic phosphodiesterase type 5 (PDE-5) inhibitors including sildenafil, tadalafil and vardenafil. The method was applied to the analysis of dietary supplements and bulk herbal materials. Bulk powders or composites of tablets, capsules or Liquids were prepared and an extraction of PDE-5 inhibitors was performed using a mixture of acetonitrile and water with sonication. Identification of sildenafil, vardenafil or tadalafil was accomplished using a single quadrupole mass spectrometer coupled to a Liquid Chromatograph with an electrospray interface. Positive ion detection in the full scan mode was used while in-source collision induced dissociation (CID) provided several structurally significant fragment ions to aid in the mass spectral identification. Approximately half of the 40 botanical products analyzed were found to contain undeclared synthetic PDE-5 inhibitors. For products found to contain one of these three compounds by LC-MS, HPLC with UV detection was used for quantitation.