Abstract Size exclusion chromatography (SEC) on irregular silicas of 5–10 um particle size and 60–130 Å average pore size is shown to provide a rapid method for the comparison of a variety of forensically significant samples. Use of dual detectors (UV/fluorescence of UV/Refractive Index) was found to enhance the value of the technique for forensic screening. 相似文献
Abstract Porous glass packing materials of average particle diameter 5 μm have been packed into a 7.2 mm i.d. x 25 cm column by viscousslurry packing parocedure. Average pore diameters of porous glasses were 170 Â, 500 Â, 1000 A, and 2000 A. The numbers of theoretical plates were between 7000 and 8000 per a column for porous glasses of pore diameters of 170, 500, and 1000 A, and 5000 for that of 2000 A. The retention volumes of narrow molecular weight-distribution polystyrene standards have been determined using tetrahydrofuran as mobile phase for the construction of calibration curves. Separations of polystyrene over molecular weight ranges of 1000 and 4,000,000 have been obtained by combining all four porous glass columns in series. Molecular weight averages of NBS 706 polystyrene have been measured and compared with the values determined with polystyrene gel columns. Both results were equivalent to the manufacturer's data. Porous glasses thus appear to be a useful packing materials for HPSEC. 相似文献
Abstract A selective HPLAC stationary phase for the separation of sterols was achieved by the chemical bonding of tomatine to microporous silica. Columns packed with tomatine silica have given promising results indicating their usefulness as well for selective on-column enrichment as for HPLC separations. Good separation was achieved with a mixture of five sterols known as oxidation products of cholesterol. 相似文献
Abstract Low molar mass PVC was isolated by Soxhlet extraction followed by gel filtration. Individual oligomer species from pentamer to decamer in this low molar mass fraction have been separated by high performance size exclusion chromatography in an alternate pumping recycle system with high efficiency columns (5 μm, 50Å column packing). 相似文献
Abstract Size exclusion chromatography of small molecules has been investigated with high efficiency columns of crosslinked polystyrene. Performance evaluations and calibrations have been determined in toluene and in tetrahydrofuran, and the effect of the solvents on solute retention is discussed. Oligomer separations of samples obtained in the thermal degradation of several polymeric materials are reported, and the utility of the technique for polymer degradation studies is clearly evidentiated. 相似文献
Abstract The influence of eluant flow rate on efficiency in reverse-phase and ion-exchange high performance liquid chromatography of proteins was studied. Both isocratic and gradient elution led to the same conclusions. The use of flow rates much lower than those generally employed was found to be important for the efficient separation of large and small proteins. Several eluant systems were also examined to determine the effects these had on the efficiency of the reverse-phase separation of proteins. 相似文献
Abstract Cleanup methods have been developed which allow utilization of modern chromatographic techniques and instrumental readouts. A cellulose cleanup for organo-phosphorus pesticides and carbamates has already been reported. A particulate carbon column has been described for Rumensin. These columns maybe combined to improve the cleanup for organophosphorus and carbamate pesticides. This same column cleanup maybe used for Ochratoxin. Powder charcoal maybe used for the mycotoxins aflatoxin, and zearalencne. It maybe used for T-2 toxin and trichothecenes with some loss (50-75% recovery). The thin layer plates themselves provide a background reference for spectroscopy. This background maybe removed by “annealing” the plates at 400°C for 2 hours. Sweepco distillation maybe used to cleanup biological samples so that carbamates and organophosphorus pesticides maybe analyzed by thin layer chromatography. Trichothecenes mycotoxins maybe cleanuped with about 40% loss. 相似文献
An on-line SPE-HPLC method using a cigarette filter as the sorbent was developed and applied to analyze the aniline derivatives in water samples. A preconcentration column packed with cigarette filters was used to replace a conventional sample loop on the injector valve of an HPLC for on-line SPE. With the consumption of a 7.5 mL sample solution, the enhancement factors ranged from 287 to 349 in comparison with direct injections of 20 μL sample solution. The detection limits (S/N = 3) for preconcentration of 7.5 mL of sample solution ranged from 0.27 to 5.46 μg/L at a sample throughput of 6 samples per hour. 相似文献
One difficult problem in the analysis of peptide modifications is quantifying isomeric modifications that differ by the position of the amino acid modified. HPLC separation using C18 reverse phase chromatography coupled with electron transfer dissociation (ETD) in tandem mass spectrometry has recently been shown to be able to relatively quantify how much of a given modification occurs at each amino acid position for isomeric mixtures; however, the resolution of reverse phase chromatography greatly complicates quantification of isomeric modifications by ETD because of the chromatographic separation of peptides with identical modifications at different sequence positions. Using peptide oxidation as a model system, we investigated the use of size exclusion chromatography coupled with ETD fragmentation to separate peptide sequences. This approach allows for the benefits of chromatographic separation of peptide sequences while ensuring co-elution of modification isomers for accurate relative quantification of modifications using standard data-dependent acquisitions. Using this method, the relative amount of modification at each amino acid can be accurately measured from single ETD MS/MS spectra in a standard data-dependent acquisition experiment.
