Retention on multiwalled carbon nanotubes (MWCNTs) in RPLC has been correlated with solute descriptors of dispersion, polarizability, dipolarity, hydrogen bond donor acidity, and hydrogen bond acceptor basicity through the use of the linear solvation energy relationship. Intermolecular interactions influencing solute retention on MWCNTs were compared with those on a graphitic carbon-deposited zirconia and a common RPLC stationary phase, octylsilane-bonded silica.
HPLC based on chiral stationary phases (CSPs) has become one of the most attractive approaches to chiral separations, due to their simplicity for determining optical purity and easy extension to the semipreparative and preparative scales. 1 One of the major problems in using many CSPs is their narrow range of analyte applicability; they can only discriminate a limited number of specific types of chemical entities, and it is frequently necessary to derivatize the compounds of interest to achieve separation. 2 On the other hand, the polysaccharide derivative-based CSPs developed by Okamoto and coworkers [3][4][5][6][7] have proven to be highly versatile and rugged. Okamoto reported that the resolution of 483 racemic mixtures on cellulose and that 80% of them were successfully resolved on either the cellulose or amylose tris(3,5-dimethylphenylcarbamate) (CDMPC or ADMPC). 8 Silica is the most popular choice for support of HPLC stationary phase ligands due to the mechanical strength, wide range of particle and pore dimensions, pore structure and wellestablished silane chemistry. However, silica and bonded phase ligands have stability problems. Silica dissolves in mobile phase buffered at or above pH 8 with loss of bonded phase ligand and column packing. 9 Loss of organosilanes from the silica surface via hydrolysis proceeds rapidly at low pH (< 3) and at high temperature (≥ 40˚C). These deficiencies of the column packing create problems of poor injection reproducibility, poor peak shape, and high backpressure, thus making method development tasks difficult. Siloxane-bonded silica phases with improved hydrolytic stability at extreme pH for use in reversedphase liquid chromatography were introduced. 10-13 However, careful choices of operating conditions, such as the use of acetonitrile instead of methanol, the use of boric acid or organic buffers in low concentration and low temperature, are still required to achieve acceptable column lifetimes. [14][15][16][17] Zirconia particles are very robust material; they show no detectable signs of dissolution over the pH range from 1 to 14 and have been used for prolonged periods at temperatures up to 200˚C in chromatographic separations. Thus, zirconia has received considerable attention as a stationary phase support for HPLC over the last decade. 18,19 One of us has been working to develop efficient and chemically stable CSPs on zirconia substrates. [20][21][22][23] Bare zirconia cannot be covalently modified like silica due to the instability of Zr-C and Zr-O-Si bonds in water. 24 Zirconia-based CSPs reported have thus been prepared by coating chiral selectors on zirconia surface by utilizing Lewis acid-base chemistry. Recently we reported chiral separation of N- (2,4-dinitrophenyl) Porous zirconia particles are very robust material and have received considerable attention as a stationary phase support for HPLC. We prepared cellulose dimethylphenylcarbamate-bonded carbon-clad zirconia (CDMPCCZ) as a chiral stationary phase (CSP) for separation of enantiomers of a set of...
Zirconia is known to be one of the best materials for the chromatographic support due to its excellent chemical, thermal, and mechanical stability. In this work, we report preparation and use of 9-O-(phenyloxycarbonyl)quinine-bonded carbon-clad zirconia (QNCZ) as a chiral stationary phase (CSP) for separation of N-(2,4-dinitrophenyl) (DNP)-amino acids (AAs) enantiomers in reversed-phase liquid chromatography. Retention and enantioselectivity of the QNCZ CSP were compared with those of quinine 3-triethoxysilylpropylcarbamate-coated zirconia (QNZ) and quinine 3-triethoxysilylpropylcarbamate-bonded silica (QNS). The QNCZ CSP showed in general the better enantioselectivity for most of the amino acids studied.
Purpose The purpose of this study was to investigate differences among perfectionism, anxiety, and aggression in contact and non-contact sports and verify the structural relationship model of perfectionism, anxiety, and aggression in the field of sports. Methods Male college athletes (N=299) participated in the study and perfectionism, anxiety, and aggression questionnaires were utilized after their verification of validity and reliability were conducted. The descriptive statistical analysis, the multivariate analysis, the correlation analysis, the structural equation analysis, and the multi-group analysis were conducted. Results The results are as follows: First, the level of perfectionism, anxiety, and aggression were significantly different between contact and non-contact sports (F=4.316, p<.001). Additionally, subfactors of aggression such as hostility, physical aggression, and verbal aggression factors in contact sports showed a higher average than non-contact sports. Second, perfectionism positively affected anxiety (t=6.936, p<.001) and anxiety positively affected aggression (t=3.380, p<.001). Moreover, the complete mediation effect of anxiety was found in the path from perfectionism to aggression (β=.152, p<.01). Finally, we compared path coefficients between contact and non-contact sports. As a result, positive causal relationships was indicated in the path from anxiety to aggression (β=.511, p<.001) in contact sports. However, it was not discovered in non-contact sports (β=.149, p>.05). Conclusions In conclusion, perfectionism causes anxiety and anxiety is a mediator leading to aggression in sports. Such effect is more predictable and observable in contact sports in which aggression is more favorable and encouraged. Implications and suggestions for future research are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.