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ABSTRACT: The effectiveness of microwave-assisted extraction of proteins from human hair samples was evaluated. Extractions were performed from 2-mg hair samples in an extraction solution consisting of 25 mM Tris-HCl (pH 8.5), 2.6 M thiourea, 5 M urea, and 5% mercaptoethanol. During extraction, samples were exposed to microwave radiation (600 W) for a specified incubation period (5-120 min). The extraction efficiency of samples that had been incubated for 60 min was similar to that of samples that had been heated at 50°C for 24 h using the conventional Shindai method.
Analytical Biochemistry 12/2010; 407(2):281-3. · 3.00 Impact Factor
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ABSTRACT: An analytical method has been developed for measuring 118 pesticides in vegetable juice. The extraction of pesticides was carried out based on dispersive solid-phase extraction, and determination was performed using gas chromatography with mass spectrometric detection (GC-MS-SIM) and liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Pesticides were confirmed by their retention time and their quantification and identification ions by GC-MS-SIM or multiple reaction monitoring of two fragment ions by LC/ESI-MS/MS, respectively. Spiking experiments from 10 to 120 microg/kg were carried out to determine the recovery, precision, and limit of quantification (LOQ) of the method. The overall recoveries of all pesticides were between 77 and 114% with relative standard deviations lower than 14%. The LOQ for most compounds was below 5 microg/kg. The proposed method was applied successfully for the residue determination of the 118 pesticides in commercial vegetable juice samples.
Journal of Agricultural and Food Chemistry 11/2009; 57(21):10095-101. · 2.82 Impact Factor
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ABSTRACT: This work reports a rapid, specific and sensitive multi-residue method based on the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method and gas chromatography with mass spectrometric detection in the selected ion monitoring mode (GC-MS-SIM) using one quantification ion and two identification ions for the routine analysis of 203 pesticides in rice paddies. Analyses of fortified rice paddy samples were performed at different levels (0.05, 0.20 and 0.50 mg kg(-1)). Mean recoveries from five replicates ranged from 75% to 115%, with coefficients of variation lower than 17%. The limit of quantification was in the range of 0.002-0.05 mg kg(-1) for the pesticides. 1040 rice paddy samples were analyzed for method application.
Analytica chimica acta 07/2008; 619(1):67-74. · 4.31 Impact Factor
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ABSTRACT: A simple, rapid, and sensitive assay of nicotine in tobacco has been developed using pyrolysis-gas chromatography-mass spectrometry (DSP-GC-MS). The optimum pyrolyzer (desorption) conditions, using Korean tobacco grade B1O (0.4 mg) and n-heptadecane as an internal standard, were found to be heating from 50 to 300 degrees C at a rate of 60 degrees C/min. Replicate determinations (n = 5), on the same tobacco and using n-heptadecane as the internal standard, resulted in a nicotine content of 1.96%, with a relative standard deviation (RSD) of 1.9%. This result was in good agreement with those from established methods: the Cai ether extraction method, a chloroform extraction method, and the CORESTA recommended method. However, the DSP method requires less than half the time of the solvent extraction methods, requires less sample, is almost solvent-free, and is less labor-intensive. The DSP method was used to determine the nicotine content of eight flue-cured tobaccos from Brazil, China, Korea, and the United States, which were found to have contents ranging from 1.21 to 2.19%.
Journal of Agricultural and Food Chemistry 03/2007; 55(4):1097-102. · 2.82 Impact Factor
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ABSTRACT: A rapid, specific and sensitive multiresidue method based on the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method and gas chromatography with mass spectrometric detection by selected ion monitoring (GC/MS-SIM) has been developed for the routine analysis of 109 pesticides in rice. The method uses one quantification ion and two identification ions. Temperature control during sample preparation helps improve the recovery of thermally labile pesticides such as captan. The method was validated by the analysis of samples spiked at 0.025-0.150 mg/kg in rice matrix. The recoveries of all pesticides were between 80% and 115% with a relative standard deviation of less than 15%. The limit of quantitation (LOQ) for most compounds met the maximum residue limits (MRLs) for pesticides in rice in Korea.
Rapid Communications in Mass Spectrometry 02/2007; 21(18):3115-22. · 2.79 Impact Factor
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ABSTRACT: The optimum conditions for the analysis of the volatile organic components of pine needles from Pinus densiflora using double-shot pyrolysis-gas chromatography-mass spectrometry (DSP-GC-MS) were investigated with respect to thermal desorption temperature and duration of heating. A total of 41 compounds were identified using thermal desorption temperatures of 150 degrees C, 200 degrees C, 250 degrees C and 300 degrees C. Thermal decomposition products, which include acetol, acetic acid, furfurals and phenols, were observed only at thermal desorption temperatures exceeding 250 degrees C: they were not observed in the extract from a simultaneous distillation extraction (SDE) method. Heating times of 1 s, 6 s, 30 s, 150 s and 300 s were investigated at the thermal desorption temperature of 200 degrees C, whence it was found that thermal decomposition products were produced only at heating times over 30 s. The optimum pyrolyzer conditions for the analysis of pine needles using DSP-GC-MS is 200 degrees C for 6 s. Under these conditions, this method gives comparable results to the SDE method.
Journal of Chromatography 10/2005; 1089(1-2):227-34. · 4.53 Impact Factor
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ABSTRACT: A rapid, sensitive and selective method involving reversed-phase liquid chromatography (LC) with electrospray ionization (ESI) mass spectrometry (MS) was employed for determination of commercial ceramides in cosmetics for quality control of the product formulation. Using this LC/ESI-MS technique, simultaneous separation and characterization of ceramides and an impurity substance were possible. Informative fragmentation patterns were obtained by employing LC/ESI-MS in both positive and negative ionization modes to identify the structures of both sphingoid base and N-acyl chains of ceramides, and also of an impurity. The combination of positive and negative mass spectra can be used for unambiguous confirmation of ceramides and for characterization of unknown species. In-source collision-induced fragmentation resulted in characteristic product anions for the ceramides containing a phytosphingosine moiety at m/z 267, 255 and 225, and for those with a sphingosine moiety at m/z 263 and 237, regardless of the length of the fatty acyl chains. The detection limit was about 0.5 pmol in selected-ion monitoring mode. Quantification using internal standards showed good linearity and a relative standard deviation of 4%. These ceramides were more sensitively detected in positive than in negative ion mode.
Rapid Communications in Mass Spectrometry 02/2003; 17(1):64-75. · 2.79 Impact Factor
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ABSTRACT: A rapid, specific and sensitive multiresidue method based on the modified Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method and gas chromatography with the electron impact mass spectrometric detection in the selected ion monitoring mode (GC–MS-SIM) using one target and two qualifier ions for the routine analysis of 107 pesticides in cabbage and radish has been developed. The recoveries for all the pesticides studied were from 80% to 115% with relative standard deviation lower than 15% in the concentration range of 0.030–0.360 mg/kg. The limit of quantitation (LOQ) for most compounds met MRLs for pesticides in cabbage and radish in Korea. This method was successfully applied to analysis commercial cabbage and radish samples.
Food Chemistry.
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ABSTRACT: A multi-residue method using liquid–liquid extraction (LLE) followed by centrifugation, freezing and dispersive solid phase extraction (dispersive SPE) as clean up steps and gas chromatography with mass spectrometric detection has been developed for the determination of trace levels of 95 pesticides in soybean oil. LLE has been optimized to extract these pesticide residues from soybean oil by studying the effect of different partitions between (i) acetonitrile (MeCN) saturated with petroleum ether and a soybean oil solution dissolved in petroleum ether saturated with MeCN, (ii) partition between MeCN and a soybean oil solution dissolved in petroleum ether saturated with MeCN, (iii) partition between MeCN and a soybean oil solution dissolved in petroleum ether, (iv) partition between MeCN saturated with n-hexane and a soybean oil solution dissolved in n-hexane saturated with MeCN, (v) partition between MeCN and a soybean oil solution, (vi) partition between MeCN and a soybean oil solution dissolved in n-hexane and (vii) partition between MeCN and a soybean oil solution dissolved in mixture of acetone and n-hexane (3:2) to the highest recovery yield of pesticides and the lowest co-extract fat residue in the final extract. Experiments were carried out in order to study the efficiency of using centrifugation and freezing steps as well as the used of primary secondary amine (PSA), florisil, graphite carbon black (GCB) and C18 for dispersive SPE on clean up stages to minimize the co-extract fat. The recoveries obtained ranged from 80 to 114% and the relative standard deviation (RSDs) from 2 to 14% for spiking levels of 0.040, 0.080 and 0.160 mg kg− 1. The limits of quantification (LOQs) of almost all compounds were below the maximum residue limits (MRLs) established by the Korean legislations for soybean oil.
Microchemical Journal.
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ABSTRACT: A rapid, specific and sensitive multiresidue method based on dispersive solid phase extraction sample preparation and gas chromatography with the mass spectrometric detection for the analysis of 234 pesticides in Korean herbs (Acanthopanax senticosus, Morus alba L., Hovenia dulcis) has been developed. Method recoveries were found to be between 62 and 119% with relative standard deviation lower than 21% for all compounds in the concentration range of 0.05 to 0.400 mg kg− 1. Limits of quantification of most compounds are below 0.050 mg kg− 1. The data demonstrate that this method was successfully used for analysis of 234 pesticides in Korean herbs.
Microchemical Journal.
