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61.
62.
Two different injectors, a split/splitless injector and a programmed temperature vaporizer (PTV) injector were investigated as the interface in on-line supercritical fluid extraction (SFE)-capillary gas chromatography (cGC). The parameters affecting the chromatographic peak shapes as well as the quantitative performance of the interfaces in on-line SFE-cGC were identified and studied. Particular attention was paid to the case where modified extraction fluids were used. Experiments were performed on two different samples. The first sample consisted of PAHs spiked on sand at different concentration levels. The other sample was a polymeric material. 相似文献
63.
Bhaskar M Gnanamani A Ganeshjeevan RJ Chandrasekar R Sadulla S Radhakrishnan G 《Journal of chromatography. A》2003,1018(1):117-123
Extracellular fluid protein (ECFP) of Streptomyces species SS07 has been used to reduce water soluble azo dyes and the carcinogenic amines released have been compared with that from chemical reduction. The effect of temperature, pH and contact time on the recovery of amines using ECFP was studied. The ECFP releases carcinogenic amines at a pH of 9.2 and a temperature of 37 degrees C for a contact period of 24 h. The reduction products were analyzed with HPLC and their structures confirmed by LC-MS and GC-MS. It was observed that both the ECFP and chemical reduction methods released similar type of amine products. In the case of dye samples, compared to chemical reduction, 5-20% increase in the release of carcinogenic amines by ECFP was observed. The percentage of amine products released by chemical reduction was higher for leather garment samples compared to ECFP treatment. 相似文献
64.
Summary High-performance capillary electrophoresis (HPCE or CE) is an ultrasensitive analytical technique with high resolving power and a wide area of applications including peptide/protein analysis. Its applicability is greatly enhanced by the short separation times, the ease of method development and the minimum sample and organic solvent requirements. Various HPCE modes have been developed for peptide/protein analysis, including capillary zone electrophoresis, micellar elektrokinetic capillary chromatography, capillary isoelectric focusing, isotachophoresis, capillary gel electrophoresis and microemulsion elektrokinetic chromatography. HPCE can easily be applied to quality control of manufacturing processes or to clinical routine for diagnostic purposes due to its potential to provide information on the identity, the purity of the samples and the quantities of the constituents. Furthermore, interactions of a peptide or a protein with other molecules can be studied by HPCE. The separation principles of the various operation modes applied to peptide/protein analysis are presented in this article. Furthermore, in order to exemplify the application of the separation principles in the area of serum protein analysis, which is of importance in clinical practice, the capillary electrophoretic methods developed for analysis of serum and cerebrospinal fluid proteins are also reviewed.Presented at: International Symposium on Separation and Characterization of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, February 5–7, 2003 相似文献
65.
Dietger Leyendecker Dagmar Leyendecker Franz P. Schmitz Ernst Klesper 《Chromatographia》1987,23(1):38-42
Summary In supercritical fluid chromatography (SFC), the elution behavior of styrene oligomers in pentane depends greatly on the degree of oligomerization, n. The influence of capacity ratio, k, on the lower oligomers up to about n=11 resembles the behavior of other substrates of low molecular weight, like aromatic hydrocarbons. Thus, with pentane of 100 bar and below, minima are found in plots of k versus temperature. In contrast, the k of oligomers of higher molecular weight (n>11) increase monotonously with increasing temperature. The studies were performed using oligostyrene fractions obtained by semipreparative SFC fractionation. 相似文献
66.
67.
Kenneth E. Laintz Shuichi Iso Yoshiro Meguro Zenko Yoshida 《Journal of separation science》1994,17(8):603-606
The chromatographic behaviors of lanthanide chelates of acetylacetone (ACAC), trifluoroacetylacetone (TFA), thenoyltrifluoroacetone (TTA), dipivaloylmethane (THD), 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione (FOD), and the thenoyltrifluoroacetonepyridine (TTA·Py) adduct were investigated using packed column supercritical fluid chromatography. Mobile phases consisting of neat and alcohol modified CO2 were used with a phenyl packed stationary phase. Lanthanide complexes of ACAC, THD, and FOD were shown to have better chromatographic performance compared to the corresponding chelates with TFA, TTA, and TTA·Py. In particular, TTA complexes such as Eu(TTA)3 showed characteristic thermal decomposition in the mobile phase at elevated temperature. In addition, retention behavior was found to be a temperature dependent function of volatility and solubility for all chelates studied. 相似文献
68.
Summary Liquid crystal polysiloxane stationary phases were prepared by coating two different polymers on deactivated porous silica particles (10 m diameter, 80 Å pores). Deactivation of the silica particles before coating was necessary to prepare highly efficient and inert stationary phases for supercritical fluid chromatography (SFC). Fat-soluble vitamins E, A, K1, K2, D2, and D3 were separated on these columns using neat supercritical CO2 as mobile phase. The analyses were completed within 40 min at 70 °C. The results were compared to those obtained using a capillary column packed with less ordered liquid crystalm,m-cyanobiphenyl-substituted polysiloxane coated particles. Reduced shape selectivity was observed with this cyanobiphenyl phase. The response factors of vitamins A, E, K1, K2, D2, and D3 when using the flame ionization detector (FID) were determined to be very similar. 相似文献
69.
J. David Pinkston Thomas E. Delaney Donald J. Bowling Thomas L. Chester 《Journal of separation science》1991,14(6):401-406
Components of hamster feces ranging from low molecular weight fatty acids through the expected range of triglycerides have been eluted in a single SFC run with simultaneous pressure and temperature programming. Temperature programming from 140°C to 240°C was required to provide optimum conditions for separation of the fatty acids and to move the elution region of the sterol esters away from that of the triglycerides. Data from chemical ionization and electron impact mass spectrometry of compounds separated by SFC were used to confirm identities suggested by retention measurements and to provide tentative identities of unknown compounds. SFC with flame ionization detection was used to compare Soxhlet extraction, off-line supercritical fluid extraction (SFE), and on-line SFE of the feces. Although samples obtained by Soxhlet extraction and SFE produced very similar chromatograms, SFE required far less time and consumed much smaller quantities of organic solvent. 相似文献
70.
Traditionally, the application of supercritical fluid chromatography has been limited to compounds of relatively low polarity.
Thus, we report here that one secondary amine and two quaternary amine salts were successfully eluted from a Deltabond Cyano-bonded
silica column with the addition of sodium alkylsulfonate to the methanol-modified, carbon dioxide-based mobile phase. A possible
ion-pairing interaction between the positively charged analytes and the anionic part of the sulfonate additive has been proposed.
In another set of experiments, the three amine salts readily eluted from both Ethyl-pyridine-bonded silica and Amino-bonded
silica phases without the need of additive although the peak shapes were less than desirable. The addition of sulfonate salt
to the mobile phase again sharpened the peaks. In the presence of a mixture of methanol and CO2, we suggest that these stationary phases are positively charged. We describe here also for the first time the employment
of a strong silica-based anion exchange (SAX) column for supercritical fluid separation of cationic species. Two elution mechanisms
were proposed for the three amine salts depending upon whether the ionic additive was incorporated into the mobile phase.
Separation as the ion-pair was proposed with an ionic additive in the mobile phase; whereas separation of the intact amine
salt from the positively charged basic stationary phases was suggested to be operational without the ionic additive. 相似文献