André J. de Villiers Title: Senior Lecturer
Office: 1044 De Beers Building
Phone: +27 (0)21 808-3351
Fax: +27 (0)21 808-3360
Educational Background:
PhD, University of Stellenbosch (SA), 2004
Post-doc studies, Pfizer Analytical Research Center, Gent University (Belgium), 2004-2006
Research Emphasis:
Liquid chromatography, Gas chromatography, Wine chemistry, Mass
spectrometry, Electrophoresis
Research Summary:
The focus of the research is on new developments in the field of separation sciences. These include the areas of ultra-high pressure and high temperature liquid chromatography, comprehensive chromatographic techniques, gas chromatography-olfactometry and innovative sample preparation techniques. Within the context of Stellenbosch these techniques are applied primarily to as powerful tools in the bourgeoning new field of wine science.
Research Description:
Comprehensive chromatography:
Comprehensive chromatographic techniques are based on the coupling of two separation methods. Because orthogonal information is obtained in this manner, tremendously improved resolving power is the result. While GCxGC methods are nowadays established as powerful separation tools, complications involved in coupling liquid-based separation systems has so far limited their application. Research in our laboratory focuses on designing powerful LCxLC systems to be used together with MS detection to unravel the exceedingly complex samples such as the phenolic fractions of wine.
Ultra-high-pressure and temperature liquid chromatography:
Exciting new developments in the field of LC during recent years has lead to significant improvements in the separations achievable. These include the use of elevated pressures (up to 1000 bar) and temperatures (up to 200?C). However, each of these approaches presents practical and fundamental difficulties. Research in this field is based in the first instance on fundamental possibilities and limitations using established chromatographic theory. At the same time the promise of these methods for several real-life applications is being demonstrated.
Gas chromatography-olfactometry:
This is a new field in our group, where the aim is the use a ‘sniff-port’ and human panels as detectors (GC-olfactometry or GC-O). The human sense of smell is in most cases more sensitive than instrumental detectors, and provides additional information on the odour-active content of volatile fractions. Thus the application of GC-MS-O for flavour characterization of numerous samples, notably wine-related, opens an exciting new field of research.
The focus of the research is on new developments in the field of separation sciences. These include the areas of ultra-high pressure and high temperature liquid chromatography, comprehensive chromatographic techniques, gas chromatography-olfactometry and innovative sample preparation techniques. Within the context of Stellenbosch these techniques are applied primarily to as powerful tools in the bourgeoning new field of wine science.
Research Description: Comprehensive chromatography:
Comprehensive chromatographic techniques are based on the coupling of two separation methods. Because orthogonal information is obtained in this manner, tremendously improved resolving power is the result. While GCxGC methods are nowadays established as powerful separation tools, complications involved in coupling liquid-based separation systems has so far limited their application. Research in our laboratory focuses on designing powerful LCxLC systems to be used together with MS detection to unravel the exceedingly complex samples such as the phenolic fractions of wine.
Ultra-high-pressure and temperature liquid chromatography:
Exciting new developments in the field of LC during recent years has lead to significant improvements in the separations achievable. These include the use of elevated pressures (up to 1000 bar) and temperatures (up to 200?C). However, each of these approaches presents practical and fundamental difficulties. Research in this field is based in the first instance on fundamental possibilities and limitations using established chromatographic theory. At the same time the promise of these methods for several real-life applications is being demonstrated.
Gas chromatography-olfactometry:
This is a new field in our group, where the aim is the use a ‘sniff-port’ and human panels as detectors (GC-olfactometry or GC-O). The human sense of smell is in most cases more sensitive than instrumental detectors, and provides additional information on the odour-active content of volatile fractions. Thus the application of GC-MS-O for flavour characterization of numerous samples, notably wine-related, opens an exciting new field of research.
Selected Publications:
- G. Vanhoenacker, A. de Villiers, K. Lazou, D. De Keukeleire, P. Sandra, Comparison of high-performance liquid chromatography- and capillary electrophoresis-mass spectroscopy for the analysis of phenolic compounds in diethyl ether extracts of red wines; Chromatographia 2001 54:309-315
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A. de Villiers A, F. Lynen, A. Crouch, P. Sandra, Improved capillary electrophoresis method for the determination of organic acids in wines; Eur. Food Res. Technol. 2003 17:535-540
- A. de Villiers A, G. Vanhoenacker, F. Lynen, P. Sandra, Stir bar sorptive extraction-liquid desorption for the analysis of hop derived bitter acids in beer by Micellar Electrokinetic Chromatography; Electrophoresis 2004 25:664-669
- A. de Villiers A, G. Vanhoenacker, P. Majek, P. Sandra, Determination of anthocyanins in wine by direct injection liquid chromatography–diode array detection–mass spectrometry and classification of wines using discriminant analysis; J. Chromatogr. A 2005 1054:195-204
- A. de Villiers A, H. Lauer, S. Goodall, P. Sandra, The influence of frictional heating on temperature gradients in ultra-high pressure liquid chromatography on 2.1 mm i.d. columns J. Chromatogr. A, 2006 1113:84-91
- I. François, A. de Villiers, P. Sandra, Considerations on the possibilities and limitations of comprehensive normal phase-reversed phase liquid chromatography (NPLC x RPLC); J. Sep. Sci. 2006 29:492-498
- A. de Villiers A, F. Lestremau, R. Szucs, S. Gélébart, F. David, P. Sandra, Evaluation of ultra performance liquid chromatography. Part I: Possibilities and limitations, J. Chromatogr. A 2006 1127:60-69
- F. Lestremau, A. de Villiers A, F. Lynen, A. Cooper, R. Szucs R, P. Sandra, High efficiency liquid chromatography on conventional columns and instrumentation by using temperature as a variable: Kinetic plots and experimental verification, J. Chromatogr. A 2007 1138:120-131.
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