Pester P 33 Grundlagen und Anwendungen der Chromatographic mit iiberkritischen mobilen Phasen D. Leyendeeker Dionex GmbH, D-6108 Weiterstadt, Federal Republic of Germany Principles and applications of chromatography with supercritieal mobile phases (SFC) Die Chromatographic mit fiberkritischen mobilen Phasen (engl. Supercritical Fluid Chromatography = SFC) arbeitet mit mobi- len Phasen, die sich im tiberkritischen Aggregatzustand befin- den. Der Analysendruck und die Analysentemperatur liegen also oberhalb der kritischen Werte. Die physikalischen Eigen- schaften dieser Eluenten wie z.B. Dichte, Viskosit/it oder Diffu- sionskoeffizienten liegen in ihren Werten zwischen denjenigen von Gasen und denen von Fliissigkeiten [1]. Die L6sungsmittel- eigenschaften eines iiberkritischen Eluenten hfingen besonders stark von seiner Dichte ab, die durch die Variation von Druck und Temperatur beeinfluBt werden kann [2]. Dementsprechend ist die am h/iufigsten verwendete Methode zur Analysenoptimie- rung die Dichte- bzw. die Druckprogrammierung [3]. Das von der Firma Dionex in Europa angebotene Modell 501 von Lee Scientific erm6glicht die computerunterstiitzte Programmierung aller drei EinfluBgr6Ben. Um die Analysentemperatur m6glichst niedrig halten zu k6nnen, finden in der SFC vor allem Eluenten mit niedrigen kritischen Temperaturen Verwendung. Neben dem Standardelu- enten Kohlendioxid sind dies vor allem Distickstoffmonoxid, niedere Alkane und Ether sowie Ammoniak [4]. Das Lgsever- m6gen eines Grundeluenten kann durch die Zugabe eines Zweit- eluenten erheblich gesteigert werden. Die besonderen Einsatzgebiete der SFC gegeniiber der Gas- Chromatographie liegen in der Analyse thermolabiler Substan- zen, wie Naturstoffe oder Pesticide sowie der Untersuchung von Substratgemischen mit h6heren Molekulargewichten wie Styrol- oder Siloxanoligomerengemische oder Polyole [5]. Zu- dem unterliegt die SFC hinsichtlich der Detektion nicht den Einschr/inkungen, wie sie in der HPLC gelten. Neben UV-, IR- oder FTIR-Detektoren lassen sich ebenfalls GC-typische Detektoren wie FID-, NPD- oder MS-Detektoren einsetzen. Literatar 1. van Wasen U, Swaid I, Schneider GM (1980) Angew Chem 92:585; (1980) Angew Chem Int Ed Engl 19:575 2. Klesper E, Leyendecker D (1986) Int Lab 16:18 3. Klesper E (1978); Angew Chem 90: 785; (1978) Angew Chem Int Ed Engl 17:738 4. Randall LG (1982) Sep Sci Technol 17:1 5. Later DW, Richter BE, Felix WD, Andersen MR, Knowles DE (1986) Am Lab 18/8:108 Fresenius Z Anal Chem (1987) 327:53 9 Springer-Verlag 1987 P 34 Polymer-coating approach for HPLC stationary phases: efficiency, chemical stability, versatility J. KiJhler, G. Heinemann, P. Kolla, H. W. Stuurman, A. Deege, and G. Schomburg Max-Planck-Institut fiir Kohlenforschung, D-4330 Miilheim/Ruhr, Federal Republic of Germany Polymer-beschichtete stationiire Phasen in der HPLC: Effizienz, chemische Stabilitiit und Vielseitigkeit der Anwendung The high versatility and flexibility of HPLC for the separation of nearly all compounds which are not too volatile, too insoluble or too hydrolytically unstable is mainly due to the adaptability of phase systems. The bonding of certain chemical moieties to silica based well-defined support particles has been the major approach for the synthesis of different stationary phases. How- ever, even with superior support particles designed for high chemical and mechanical stability [1, 2] and highly reactive re- agents [3 - 5] not all silanol groups could be reacted or shielded in a way that their influence on selectivity, sometimes beneficial but frequently deleterious, has become negligible. Especially polar stationary phases are difficult to produce with a low enough residual silanol concentration and a high enough chem- ical stability, i. e., lifetime. Polymer coating techniques as applied earlier in GC have been used by our group to make the production of a stationary phase independent of the chemical nature of the support surface. In many cases polymer coating was combined with silanizations to react most of the SiOH groups and to shield the rest. Thus multiple layers were formed. Several syntheses of very different stationary phases using the "polymer coating approach" and the versatile applicability, high efficiency and chemical stability of these phases should be mentioned. It was shown how polar and non-polar substituted polysiloxanes can be synthesized by an equilibration process between poly(methylhydrosiloxane) and octamethyl cyclo tetrasiloxane followed by a platinum catalyzed hydrosilaniza- tion involving polar and non-polar olefines [6]. These starting materials were coated on silica particles and immobilized by 7- radiation or peroxide degradation. BET-data reveal that pore plugging could be avoided. The phases exhibited excellent efficiency and chemical stability. Due to the superior shielding of silanols highly sensitive compounds could be separated that normally were isomerized on other supports [7]. Cyano-sub- stituted polysiloxanes coated on silica were used for the isocratic separation of all PTH-amino acids. Poly(vinylpyrrolidone) (PVP) was immobilized on silica [8]. The phase was more stable than a pyrrolidone phase that was prepared by chemical bonding for comparison. The same PVP-phase was applied under normal-phase conditions for the separation of poly- aromatics, under reversed-phase conditions for the separation of hydroxy benzoic acids, and for gel permeation and hydrophobic interaction chromatography of proteins. Anion- and cation- exchange polymers were synthesized on the basis of derivatized polybutadienes and coated on silica and alumina supports [9]. Separations of acids, amines and inorganic cations and anions on these stationary phases were carried out. Special emphasis is laid on the superior pH-stability of polybutadiene coated alumina. Highly basic amines can be separated with very high efficiency in a pure reversed-phase mode at an eluent pH-vatue of around 12, 53