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In an e f f o r t t o p r o t e c t xilobam from t h e e f f e c t s of h i g h temperatures and h i g h h u m i d i t i e s w i t h o u t a d v e r s e l y a f f e c t i n g i t s d i s s o l u t i o n from t a b l e t s , t h r e e a r y l s u l f o n i c a c i d s a l t s and t h e s a c c h a r i n s a l t were p r e p a r e d . A l l o f t h e s a l t s were determined t o be more s t a b l e a t 74% r e l a t i v e humidity and 70' t h a n t h e f r e e b a s e .I n s p i t e of t h e l a r g e d i f f e r e n c e s between t h e e f f e c t of h i g h humidity a t a h i g h temperature on t h e s a l t s v e r s u s t h e f r e e b a s e , t h e

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Chemically bonded stationary phases for high pressure Iiquld chromatography (HPLC) have been used In a variety of applications. In previous work, we have described a slmpie and totally In-situ process for preparing bonded phases for high pressure iiquld chromatographic use. Columns were prepared by reaction of either octadecyltrichlorosllane or phenyltrlchiorosllane with porous layer slilca beads. Inltlaliy, pre-reaction surface moisture was controlled by drying with flowing nitrogen. However, the performance and reproducibility of bonded phase packings are controlled to a large degree by the amount of bonded material on the surface. Since the trlchlorosilanes used polymerire readily In the presence of moisture, the amount of material bonded to the silica surface can easily vary between different columns unless the amount of water Is controlled to a reproducible degree. This paper describes a set of In-situ reaction condltlons which produce columns with a better degree of reproducibility. The amount of physically adsorbed surface water was established by first pumping water-saturated toluene followed by a specified volume of dry toluene through packed columns. In addition to discussing the actual preparation technique, the general chromatographic behavior of several In-situ prepared columns has been examined.Chemically bonded stationary phases for high pressure liquid chromatography (HPLC) have been used in a variety of applications. The most familiar means of preparing these phases is by bonding various organosilane molecules to a silica type surface. Perhaps the most common of these have been the reactions of the chlorosilanes. Chlorosilanes react with surface hydroxyl groups to form bonded films of varying structure (1). A number of adsorbent modification procedures employing di-and trichlorosilanes have been used to form bonded phases for chromatographic use ( I -16).Previously several workers have described in-situ processes for preparing bonded phases for chromatographic application. Hastings et al. (7) have described a partial insitu process in which the final polymerization was carried out directly in the column. Later, Gilpin and coworkers (14,15) discussed a simple, totally in-situ process for preparing bonded phases for HPLC use. Columns were prepared by the reaction of either octadecyltrichlorosilane or phenyltrichlorosilane with porous layer silica beads (Corasil 11, 37-50 p). Advantages of the method were ease and convenience of preparation.One of the most important factors affecting the performance of bonded phase columns is the amount of material deposited on the surface (8). Since the trichlorosilanes used polymerize readily in the presence of moisture, the amount of material bonded to the silica surface can easily vary between different columns unless the amount of water is controlled to a reproducible degree.This paper describes a set of in-situ reaction conditions which produce columns with a good degree of reproducibilAuthor to whom correspondence should be addressed.ity. In addition, several...