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LC System (lc + system)
Selected AbstractsDirect characterization of aqueous extract of Hibiscus sabdariffa using HPLC with diode array detection coupled to ESI and ion trap MSJOURNAL OF SEPARATION SCIENCE, JSS, Issue 20 2009Inmaculada C. Rodríguez-Medina Abstract The phenolic fraction and other polar compounds of the Hibiscus sabdariffa were separated and identified by HPLC with diode array detection coupled to electrospray TOF and IT tandem MS (DAD-HPLC-ESI-TOF-MS and IT-MS). The H. sabdariffa aqueous extract was filtered and directly injected into the LC system. The analysis of the compounds was carried out by RP HPLC coupled to DAD and TOF-MS in order to obtain molecular formula and exact mass. Posterior analyses with IT-MS were performed and the fragmentation pattern and confirmation of the structures were achieved. The H. sabdariffa samples were successfully analyzed in positive and negative ionization modes with two optimized linear gradients. In positive mode, the two most representative anthocyanins and other compounds were identified whereas the phenolic fraction, hydroxycitric acid and its lactone were identified using the negative ionization mode. [source] Application of continual injection liquid-phase microextraction method coupled with liquid chromatography to the analysis of organophosphorus pesticidesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2009Yanuardi Raharjo Abstract A liquid-phase microextraction coupled with LC method has been developed for the determination of organophosphorus pesticides (methidation, quinalphos and profenofos) in drinking water samples. In this method, a small amount (3 ,L) of isooctane as the acceptor phase was introduced continually to fill-up the channel of a 1.5 cm polypropylene hollow fiber using a microsyringe while the hollow fiber was immersed in an aqueous donor solution. A portion of the acceptor phase (ca. 0.4 ,L) was first introduced into the hollow fiber and additional amounts (ca. 0.2 ,L) of the acceptor phase were introduced to replenish at intervals of 3 min until set end of extraction (40 min). After extraction, the acceptor phase was withdrawn and transferred into a 2 mL vial for a drying step prior to injection into a LC system. Parameters that affect the extraction efficiency were studied including the organic solvent, length of fiber, volume of acceptor and donor phase, stirring rate, extraction time, and effect of salting out. The proposed method provided good enrichment factors of up to 189.50, with RSD ranging from 0.10 to 0.29%, analyte recoveries of over 79.80% and good linearity ranging from 10.0 to 1.25 mg/L. The LOD ranged from 2.86 to 82.66 ,g/L. This method was applied successfully to the determination of organophosphorus pesticides in selected drinking water samples. [source] Determination of , -tocopherol in infant foods by liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2003Andras Kalman A novel, sensitive and specific method for the quantification of , -tocopherol in two infant foods (milk and cereals) using liquid chromatography on-line with positive atmospheric pressure chemical ionisation mass spectrometry detection (LC/APCI-MS) has been developed. The samples were first saponified in order to eliminate fats and to transform tocopherol esters into free tocopherol, followed up by a liquid,liquid extraction of the analyte in petroleum benzine/diisopropyl ether (75:25, v/v) prior to injection onto the LC system. For the quantification, deuterium-labelled tocopherol was used as internal standard and the samples were monitored in selected ion monitoring (SIM) mode. Calibration curves between 1,40,,g/mL of , -tocopherol showed a good linear correlation (r2,=,0.99994), and the detection limit was determined to be 2.5,ng/mL. The within-day and between-day precision were determined for several dietetic infant formulae and certified reference samples, and found to be below 3.5%. The accuracy determined on a Nestlé reference sample (milk powder) was calculated to be 115.2,±,1.2%, which confirms the robustness of the proposed method. This study shows that single quadrupole LC/MS can be applied for the quantification of vitamins in food and the method offers better sensitivity and selectivity than traditional method such as LC-UV. This would simplify the preparation of the food samples and consequently enhance the vitamin analysis throughput in the food area. Copyright © 2003 John Wiley & Sons, Ltd. [source] Identification of N -linked oligosaccharide labeled with 1-pyrenesulfonyl chloride by quadrupole time-of-flight tandem mass spectrometry after separation by micro- and nanoflow liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 9 2009Jun Zhe Min Abstract The development of a qualitative determination method for the N -linked oligosaccharides in glycoproteins was attempted by the combination of micro- or nanoflow LC with Q-TOF-MS/MS. The asparaginyl-oligosaccharides in glycoproteins, liberated from the treatment of Pronase E, were separated, purified and labeled with 1-pyrenesulfonyl chloride (PSC). The resulting derivatives were separated by the microflow LC system utilizing a 0.5 mm diameter microcolumn or nanoflow LC system utilizing a 75 µm diameter chip column. The eluted N -linked oligosaccharide derivatives were then introduced into the Q-TOF-MS instrument and sensitively detected in the ESI+ mode. Several factors (i.e. fragmentor, skimmer, Vcap voltages and collision energy) affecting the sensitivity of Q-TOF-MS/MS detection were optimized in both the micro- and nanoflow LC systems. Various fragment ions based on the carbohydrate units appeared on the MS/MS spectra. Among the peaks, m/z 600.16 corresponding to PSC-labeled Asp-HexNAc is the most important one to identify the asparaginyl-oligosaccharide. The N -linked oligosaccharides in the ovalbumin were easily identified by the selected-ion chromatogram at m/z 600.16 by the MS/MS detection. Therefore, the identification of N -linked oligosaccharides in glycoproteins seems to be possible by the proposed micro- and nanoflow LC separations followed by the Q-TOF-MS/MS detection. Copyright © 2009 John Wiley & Sons, Ltd. [source] Development and validation of an on-line two-dimensional reversed-phase liquid chromatography,tandem mass spectrometry method for the simultaneous determination of prostaglandins E2 and F2, and 13,14-dihydro-15-keto prostaglandin F2, levels in human plasmaBIOMEDICAL CHROMATOGRAPHY, Issue 3 2009Junji Komaba Abstract We developed and validated an on-line reverse-phase two-dimensional LC/MS/MS (2D-LC/MS/MS) system for simultaneous determination of the levels of prostaglandin (PG) E2 as well as PGF2, and its metabolite 13,14-dihydro-15-keto PGF2, (F2, -M) in human plasma. Analytes were extracted by a three-step solid-phase extraction. Samples were then analyzed by on-line 2D-LC/MS/MS with electrospray ionization in negative mode. The 2D-LC system is composed of two reverse-phase analytical columns with a trapping column linking the two analytical columns. While an acidic buffer was used for both separation dimensions, differing organic solvents were employed for each dimension: methanol for the first and acetonitrile for the second to increase resolving power. The 2D-LC/MS/MS method was highly selective and sensitive with a significantly lower limit of quantitation (0.5 pg/mL for PGE2 and 2.5 pg/mL for PGF2, and F2, -M, respectively). Linearity of the 2D-LC/MS/MS system was demonstrated for the calibration ranges of 0.5,50 pg/mL for PGE2 and 2.5,500 pg/mL for PGF2, and F2, -M, respectively. Acceptable precision and accuracy were obtained throughout the calibration curve ranges. This highly selective and sensitive method was successfully utilized to determine the endogenous levels of PGE2, PGF2,, and F2, -M in plasma samples from six (four male and two female) normal volunteers. The mean concentrations for each analyte were 0.755 pg/mL for PGE2, 5.70 pg/mL for PGF2, and 9.48 pg/mL for F2, -M. Copyright © 2008 John Wiley & Sons, Ltd. [source] Highly sensitive and quantitative analysis of polyeptides using a new gradient system based on an abrupt change in adsorption of polypeptide to the reversed-phase column packingBIOMEDICAL CHROMATOGRAPHY, Issue 10 2007Ryoya Goda Abstract During a study of 100 µL aliquots of urocortin containing various acetonitrile contents, we hypothesized that a change in the acetonitrile content in the solution across a specific content of acetonitrile (critical threshold) causes an abrupt change in adsorption capacity to the column packing. Circular dichroism measurements suggest that the conformational change induced by acetonitrile in the solution causes the abrupt change in adsorption capacity, and this solvent-induced conformational change is reversible across the critical threshold. This hypothesis can apply to various polypeptides with molecular weights range from 1007 to 6789 and to other organic solvents. A new gradient system utilizing the instant recovery of the adsorption capacity across the critical threshold was designed, and applied to the analysis of a 100 µL aliquot of various polypeptide solutions. The results suggest that use of a solution containing organic solvents more than the critical threshold allows successful dilution of polypeptides up to picomolar concentration range without any loss due to its adsorption during handling procedures and loading onto the LC system, and that a new gradient system enables quantitative analysis of polypeptides at picomolar concentrations in such solutions. Copyright © 2007 John Wiley & Sons, Ltd. [source] The benefit of the retrofitting of a conventional LC system to micro LC: a practical evaluation in the field of bioanalysis with fluorimetric detectionBIOMEDICAL CHROMATOGRAPHY, Issue 5 2003S. Roy Abstract The interests in liquid micro-chromatography (higher column efficiencies, increase in sensitivity) are now well established. The enhancement of fluorimetric response induced by the reduction of the inner diameter of columns (4.6, 3.0, 1.0 and 0.3,mm respectively) coupled with adapted detection cells to control the loss of efficiency (8,µL for the two first columns and 100,nL for the two smaller ones) has been studied in the bioanalytical field, using the plasma determination of native fluorescent antibacterial agents: fluoroquinolones. Ten-fold enhancement of the signal can easily be obtained when substituting a 0.3,mm i.d. column and 100,nL detection cell for a 4.6,mm i.d. column, and 8,µL detection cell. In addition to inner diameter reduction, the detection cell geometry appears to be an essential parameter to obtain the best enhancement of the recorded signal. Hence, the enhancement of signal with micro-chromatography with fluorimetric detection appears to be a compromise between column inner diameter and flow cell volume reduction. Copyright © 2003 John Wiley & Sons, Ltd. [source] Identification of N -linked oligosaccharide labeled with 1-pyrenesulfonyl chloride by quadrupole time-of-flight tandem mass spectrometry after separation by micro- and nanoflow liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 9 2009Jun Zhe Min Abstract The development of a qualitative determination method for the N -linked oligosaccharides in glycoproteins was attempted by the combination of micro- or nanoflow LC with Q-TOF-MS/MS. The asparaginyl-oligosaccharides in glycoproteins, liberated from the treatment of Pronase E, were separated, purified and labeled with 1-pyrenesulfonyl chloride (PSC). The resulting derivatives were separated by the microflow LC system utilizing a 0.5 mm diameter microcolumn or nanoflow LC system utilizing a 75 µm diameter chip column. The eluted N -linked oligosaccharide derivatives were then introduced into the Q-TOF-MS instrument and sensitively detected in the ESI+ mode. Several factors (i.e. fragmentor, skimmer, Vcap voltages and collision energy) affecting the sensitivity of Q-TOF-MS/MS detection were optimized in both the micro- and nanoflow LC systems. Various fragment ions based on the carbohydrate units appeared on the MS/MS spectra. Among the peaks, m/z 600.16 corresponding to PSC-labeled Asp-HexNAc is the most important one to identify the asparaginyl-oligosaccharide. The N -linked oligosaccharides in the ovalbumin were easily identified by the selected-ion chromatogram at m/z 600.16 by the MS/MS detection. Therefore, the identification of N -linked oligosaccharides in glycoproteins seems to be possible by the proposed micro- and nanoflow LC separations followed by the Q-TOF-MS/MS detection. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||