The Experts below are selected from a list of 23310 Experts worldwide ranked by ideXlab platform
Ana Vazquez - One of the best experts on this subject based on the ideXlab platform.
-
analysis of free and esterified sterols in edible oils by online reversed phase liquid Chromatography gas Chromatography rplc gc using the through oven transfer adsorption desorption totad interface
Food Chemistry, 2012Co-Authors: Rosa M Toledano, Jose M Cortes, Jesus Villen, Angela Rubiomoraga, Ana VazquezAbstract:An online reversed phase liquid Chromatography-gas Chromatography (RPLC-GC) method is proposed to quantify free, total and esterified sterols of edible oils. To determine free sterols the diluted oils are injected into the liquid Chromatograph, where free sterols are separated from triglycerides and the sterol fraction is automatically transferred to the gas Chromatograph to be analysed. To determine total sterols the samples were saponified with potassium hydroxide in ethanolic solution and the unsaponifiable fraction was extracted with diethyl ether. The extract was then analysed by RPLC-GC, avoiding the laborious thin layer Chromatography step used in the Official European Union (EU) Method. The relative standard deviations (RSDs) from the absolute peak area varied from 7.6% to 15.8%. Limits of detection (LODs) were less than 8.5 mg/kg. No variability in retention time was observed. The method was applied to the determination of total sterols in edible oil samples and the results were compared with those obtained with the Official EU Method. Good agreement was found between both methods, except in the case of campesterol.
-
analysis of pesticides in nuts by online reversed phase liquid Chromatography gas Chromatography using the through oven transfer adsorption desorption interface
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Jose M Cortes, Jesus Villen, Rosa M Toledano, Ana VazquezAbstract:A new method to determine pesticide residues in nuts is presented, in which the pesticides are extracted from samples with a small amount of ethyl acetate and anhydrous sodium sulfate. No additional cleanup or concentration steps are necessary. The extract is directly injected into the high-pressure liquid Chromatograph, where preseparation of the pesticide residues from other components coextracted from the nuts is carried out using methanol/water as the eluent. The selected liquid Chromatography fraction containing the pesticides is automatically transferred to the gas Chromatograph using the through-oven transfer adsorption/desorption interface. The calculated limits of detection for each pesticide varied from 0.1 to 61.3 microg/kg. The repeatabilities of the analysis and the overall procedure (extraction and analysis) were satisfactory. No variations in the retention time were observed. The method was applied to the analysis of pistachio nut, peanut, walnut, hazelnut, and sunflower seed.
-
determination of organophosphorus and triazine pesticides in olive oil by on line coupling reversed phase liquid Chromatography gas Chromatography with nitrogen phosphorus detection and an automated through oven transfer adsorption desorption interfa
Journal of AOAC International, 2005Co-Authors: Raquel Sanchez, Jose M Cortes, Jesus Villen, Ana VazquezAbstract:: A method is described for the simultaneous determination of organophosphorus and triazine pesticides in olive oil, whereby reversed-phase liquid Chromatography (LC) is coupled to gas Chromatography by means of an automated through-oven transfer adsorption-desorption (TOTAD) interface. The olive oil needs to be filtered only before it is loaded into the liquid Chromatograph, where preseparation of the pesticide residues from the other olive oil components is carried out by using methanol-water as the eluant. The LC fraction containing the pesticides is automatically transferred to the gas Chromatograph by using the TOTAD interface, which almost totally eliminates the solvent, so that water-sensitive detectors such as the nitrogen-phosphorus detector can be used. Detection limits range from 0.07 to 0.38 microg/L for organophosphorus pesticides and from 6.0 to 7.0 microg/L for triazines. The results were compared with those obtained by flame ionization detection.
-
direct analysis of pesticide residues in olive oil by on line reversed phase liquid Chromatography gas Chromatography using an automated through oven transfer adsorption desorption totad interface
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Raquel Sanchez, Ana Vazquez, David Riquelme, Jesus VillenAbstract:A fully automated on-line reversed phase liquid Chromatography-gas Chromatography system is described. The system uses a prototype of the automated through oven transfer adsorption desorption interface. The system is demonstrated by presenting a new rapid method for the determination of pesticide residue in olive oil, which is injected directly with no sample pretreatment step other than filtration. Methanol:water is used as the eluent in the LC preseparation step, while the LC fraction containing the pesticide is automatically transferred to the gas Chromatograph. Detection limits of pesticides varied from 0.18 to 0.44 mg/L when a flame ionization detector was used. As an example, relative standard deviation and linear calibration are presented for terbutryne.
Jesus Villen - One of the best experts on this subject based on the ideXlab platform.
-
analysis of free and esterified sterols in edible oils by online reversed phase liquid Chromatography gas Chromatography rplc gc using the through oven transfer adsorption desorption totad interface
Food Chemistry, 2012Co-Authors: Rosa M Toledano, Jose M Cortes, Jesus Villen, Angela Rubiomoraga, Ana VazquezAbstract:An online reversed phase liquid Chromatography-gas Chromatography (RPLC-GC) method is proposed to quantify free, total and esterified sterols of edible oils. To determine free sterols the diluted oils are injected into the liquid Chromatograph, where free sterols are separated from triglycerides and the sterol fraction is automatically transferred to the gas Chromatograph to be analysed. To determine total sterols the samples were saponified with potassium hydroxide in ethanolic solution and the unsaponifiable fraction was extracted with diethyl ether. The extract was then analysed by RPLC-GC, avoiding the laborious thin layer Chromatography step used in the Official European Union (EU) Method. The relative standard deviations (RSDs) from the absolute peak area varied from 7.6% to 15.8%. Limits of detection (LODs) were less than 8.5 mg/kg. No variability in retention time was observed. The method was applied to the determination of total sterols in edible oil samples and the results were compared with those obtained with the Official EU Method. Good agreement was found between both methods, except in the case of campesterol.
-
analysis of pesticides in nuts by online reversed phase liquid Chromatography gas Chromatography using the through oven transfer adsorption desorption interface
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Jose M Cortes, Jesus Villen, Rosa M Toledano, Ana VazquezAbstract:A new method to determine pesticide residues in nuts is presented, in which the pesticides are extracted from samples with a small amount of ethyl acetate and anhydrous sodium sulfate. No additional cleanup or concentration steps are necessary. The extract is directly injected into the high-pressure liquid Chromatograph, where preseparation of the pesticide residues from other components coextracted from the nuts is carried out using methanol/water as the eluent. The selected liquid Chromatography fraction containing the pesticides is automatically transferred to the gas Chromatograph using the through-oven transfer adsorption/desorption interface. The calculated limits of detection for each pesticide varied from 0.1 to 61.3 microg/kg. The repeatabilities of the analysis and the overall procedure (extraction and analysis) were satisfactory. No variations in the retention time were observed. The method was applied to the analysis of pistachio nut, peanut, walnut, hazelnut, and sunflower seed.
-
determination of organophosphorus and triazine pesticides in olive oil by on line coupling reversed phase liquid Chromatography gas Chromatography with nitrogen phosphorus detection and an automated through oven transfer adsorption desorption interfa
Journal of AOAC International, 2005Co-Authors: Raquel Sanchez, Jose M Cortes, Jesus Villen, Ana VazquezAbstract:: A method is described for the simultaneous determination of organophosphorus and triazine pesticides in olive oil, whereby reversed-phase liquid Chromatography (LC) is coupled to gas Chromatography by means of an automated through-oven transfer adsorption-desorption (TOTAD) interface. The olive oil needs to be filtered only before it is loaded into the liquid Chromatograph, where preseparation of the pesticide residues from the other olive oil components is carried out by using methanol-water as the eluant. The LC fraction containing the pesticides is automatically transferred to the gas Chromatograph by using the TOTAD interface, which almost totally eliminates the solvent, so that water-sensitive detectors such as the nitrogen-phosphorus detector can be used. Detection limits range from 0.07 to 0.38 microg/L for organophosphorus pesticides and from 6.0 to 7.0 microg/L for triazines. The results were compared with those obtained by flame ionization detection.
-
direct analysis of pesticide residues in olive oil by on line reversed phase liquid Chromatography gas Chromatography using an automated through oven transfer adsorption desorption totad interface
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Raquel Sanchez, Ana Vazquez, David Riquelme, Jesus VillenAbstract:A fully automated on-line reversed phase liquid Chromatography-gas Chromatography system is described. The system uses a prototype of the automated through oven transfer adsorption desorption interface. The system is demonstrated by presenting a new rapid method for the determination of pesticide residue in olive oil, which is injected directly with no sample pretreatment step other than filtration. Methanol:water is used as the eluent in the LC preseparation step, while the LC fraction containing the pesticide is automatically transferred to the gas Chromatograph. Detection limits of pesticides varied from 0.18 to 0.44 mg/L when a flame ionization detector was used. As an example, relative standard deviation and linear calibration are presented for terbutryne.
Jose M Cortes - One of the best experts on this subject based on the ideXlab platform.
-
analysis of free and esterified sterols in edible oils by online reversed phase liquid Chromatography gas Chromatography rplc gc using the through oven transfer adsorption desorption totad interface
Food Chemistry, 2012Co-Authors: Rosa M Toledano, Jose M Cortes, Jesus Villen, Angela Rubiomoraga, Ana VazquezAbstract:An online reversed phase liquid Chromatography-gas Chromatography (RPLC-GC) method is proposed to quantify free, total and esterified sterols of edible oils. To determine free sterols the diluted oils are injected into the liquid Chromatograph, where free sterols are separated from triglycerides and the sterol fraction is automatically transferred to the gas Chromatograph to be analysed. To determine total sterols the samples were saponified with potassium hydroxide in ethanolic solution and the unsaponifiable fraction was extracted with diethyl ether. The extract was then analysed by RPLC-GC, avoiding the laborious thin layer Chromatography step used in the Official European Union (EU) Method. The relative standard deviations (RSDs) from the absolute peak area varied from 7.6% to 15.8%. Limits of detection (LODs) were less than 8.5 mg/kg. No variability in retention time was observed. The method was applied to the determination of total sterols in edible oil samples and the results were compared with those obtained with the Official EU Method. Good agreement was found between both methods, except in the case of campesterol.
-
analysis of pesticides in nuts by online reversed phase liquid Chromatography gas Chromatography using the through oven transfer adsorption desorption interface
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Jose M Cortes, Jesus Villen, Rosa M Toledano, Ana VazquezAbstract:A new method to determine pesticide residues in nuts is presented, in which the pesticides are extracted from samples with a small amount of ethyl acetate and anhydrous sodium sulfate. No additional cleanup or concentration steps are necessary. The extract is directly injected into the high-pressure liquid Chromatograph, where preseparation of the pesticide residues from other components coextracted from the nuts is carried out using methanol/water as the eluent. The selected liquid Chromatography fraction containing the pesticides is automatically transferred to the gas Chromatograph using the through-oven transfer adsorption/desorption interface. The calculated limits of detection for each pesticide varied from 0.1 to 61.3 microg/kg. The repeatabilities of the analysis and the overall procedure (extraction and analysis) were satisfactory. No variations in the retention time were observed. The method was applied to the analysis of pistachio nut, peanut, walnut, hazelnut, and sunflower seed.
-
determination of organophosphorus and triazine pesticides in olive oil by on line coupling reversed phase liquid Chromatography gas Chromatography with nitrogen phosphorus detection and an automated through oven transfer adsorption desorption interfa
Journal of AOAC International, 2005Co-Authors: Raquel Sanchez, Jose M Cortes, Jesus Villen, Ana VazquezAbstract:: A method is described for the simultaneous determination of organophosphorus and triazine pesticides in olive oil, whereby reversed-phase liquid Chromatography (LC) is coupled to gas Chromatography by means of an automated through-oven transfer adsorption-desorption (TOTAD) interface. The olive oil needs to be filtered only before it is loaded into the liquid Chromatograph, where preseparation of the pesticide residues from the other olive oil components is carried out by using methanol-water as the eluant. The LC fraction containing the pesticides is automatically transferred to the gas Chromatograph by using the TOTAD interface, which almost totally eliminates the solvent, so that water-sensitive detectors such as the nitrogen-phosphorus detector can be used. Detection limits range from 0.07 to 0.38 microg/L for organophosphorus pesticides and from 6.0 to 7.0 microg/L for triazines. The results were compared with those obtained by flame ionization detection.
Kenji Hara - One of the best experts on this subject based on the ideXlab platform.
-
detection of amphetamines in urine using head space solid phase microextraction and chemical ionization selected ion monitoring
Forensic Science International, 1995Co-Authors: Mikio Yashiki, T Kojima, Tetsuji Miyazaki, Nobuyuki Nagasawa, Yasumasa Iwasaki, Kenji HaraAbstract:An accurate, simple and rapid method for qualitative and quantitative analysis of amphetamine and methamphetamine in urine was developed using head space-solid phase microextraction and gas Chromatography-mass spectrometry/chemical ionization selected ion monitoring. A vial containing a urine sample potassium carbonate and pentadeuterated methamphetamine which was used as an internal standard was heated at 80°C for 20 min. The needle of a solid phase microextraction device was passed through the septum, and the extraction fiber in the needle was exposed for 5 min in the head space of the vial. The needle was removed from the vial and inserted into the injection port of gas Chromatograph or gas Chromatograph/mass spectrometer. The compounds adsorbed on the fiber were detached by exposing the fiber in the injection port, and analyzed. The proposed method was more than 20 times more sensitive than the conventional head space method.
Giuseppe Etiope - One of the best experts on this subject based on the ideXlab platform.
-
evaluation of a micro gas Chromatographic technique for environmental analyses of co2 and c1 c6 alkanes
Journal of Chromatography A, 1997Co-Authors: Giuseppe EtiopeAbstract:A performance evaluation of a portable gas Chromatograph (Chrompack CP2002P), equipped with a micro thermal conductivity detection (micro-TCD) system was conducted for carbonious gases of environmental relevance, by analysis of calibration standards, atmospheric air samples and bottled mineral water samples compared with air-saturated water samples. The reliability of an headspace equilibration method has also been tested for application to gas dissolved in natural waters. The instrument has been tested for its sensitivity, reproducibility, linearity and retention time stability. The miniaturization technique of the micro gas Chromatograph allows for analyses much faster than those of traditional TCD equipped gas Chromatographs: complete run time, including C6, is about 30 s. This rapidity may allow a large number of field data to be achieved over a short time and the immediate analysis on site may drive the survey strategy as the results are examined.