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Design, synthesis and evaluation of a series of alkylsiloxane-bonded stationary phases for expanded supercritical fluid chromatography separations
No full textSupercritical fluid chromatography (SFC) today represents an alternative technique in analytical chemistry due to its obvious benefits in kinetic performance and its complementarity to liquid chromatography. In this paper, a series of alkylsiloxane-bonded stationary phases were synthesized and evaluated to expand their SFC applications. Five kinds of non-endcapped C8 stationary phases (C8-1 to C8-5) with increasing bonding density were synthesized, and the carbon content was 3.91%, 6.07%, 7.97%, 8.65% and 9.10% respectively. Retention mechanism of the C8 phases in SFC in SFC was investigated by the use of a linear solvation energy relationship (LSER) model. Results underlined a close relationship between the bonding density of alkyl chain and the dispersion and polar interactions of the stationary phase. Complementary evaluation was studied based on the calculation of vector angle (theta), and the widest theta of 123 degrees was found between silica and C8 with the highest bonding density. Selective diversity also existed between the two C8 phases with the highest and lowest bonding densities. In addition, the effect of modifier on the SFC mechanism was investigated. Modifiers (methanol, ethanol, isopropanol and acetonitrile) had insignificant influence on the dispersion interaction but they mainly affected the hydrogen bonding interaction by changing the LSER parameters a and b. Finally, C8 and silica columns were applied for separation of eight amide alkaloids of Piper kadsura. Silica provided better retention but limited selectivity while C8 can distinguish alkaloids different in alkyl chain, double bond and cis-trans structure. This research further contributed to demonstrate the potential of alkylsiloxane-bonded stationary phase in improving selectivity of SFC. (C) 2019 Elsevier B.V. All rights reserved
Sino-Japanese Research Cooperative Program of Ministry of Science and Technology[2016YFE0118300]
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Integration of stable isotope labeling derivatization and magnetic dispersive solid phase extraction for measurement of neurosteroids by in vivo microdialysis and UHPLC-MS/MS
No full textIn this work, a novel strategy of stable isotope labeling derivatization (SILD) combined with magnetic dispersive solid-phase extraction (MDSPE), has been proposed for simultaneous monitoring of neurosteroids changes linked to Parkinson's disease (PD) by in vivo microdialysis. The developed method was based on ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection using multiple-reaction monitoring (MRM) mode. In this study, a new pair of stable isotope labeling reagents d(0)-/d(3)-3-N-methyl-2'-carboxyl Rhodamine 6G (d(0)-/d(3)-MCR6G), were designed and synthesized for derivatizing neurosteroids in rat blood microdialysates and neurosteroid standards, respectively. d(3)-MCR6G labeled neurosteroids standards were used as internal standard for the following pretreatment and UHPLC-MS/MS quantification to minimize the deviations caused by complex matrix and ion suppression effects in mass spectrometry analysis. Under the optimized derivatization and extraction conditions, good linearities of eight neurosteroids were obtained with correlation coefficients R-2 values > 0.98. The limits of detection (LODs) and quantitation (LOQs) ranged from 0.06 to 0.12 pg/mL and 0.30-0.40 pg/mL, respectively. Taken together, the established method exhibited high sensitivity and selectivity, excellent accuracy, convenience and high efficiency. It was applied for the simultaneous and dynamic measurement of multiple neurosteroids in normal and PD rat blood microdialysates. This method would be expected to be potentially useful for the monitoring and drug treatment of PD and related neurological disorders in the future
