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On-line process control with a SAW (surface acoustic wave) sensor-based gas-sensor microsystem (SAGAS PC = surface acoustic wave based aroma and gas analyzing system) for industrial applications is presented. The monitoring of the gradient former of a preparative HPLC system is a useful tool for the on-line process control of pilot plant production. All applications deal with the detection and subsequent qualification as well as quantitation of volatile organic compounds (VOCs), for example, organic solvents or even water, by investigating their vapor with the SAGAS PC-system. To demonstrate the suitability of the system for the above-mentioned purpose different examples of typical binary solvent mixtures for normal phase (NP) HPLC have been chosen. The accuracy, precision, and robustness of the applied method are determined, and the results meet the specification requirements. Furthermore, on-line measurements in a pilot plant environment are presented.

In the chemical industry and particularly in the pharmaceutical industry, separation, purification and refining processes have always had a very important position. Synthesis and natural processes at best seldom deliver the pure required product.The quality requirements and expected efficiency of the pharmaceutical final product have risen drastically in the last few years. This development has been initiated and imposed f rom va rious diffe rent view p o i n t s : i n c reased know l e d ge, market demands etc. Coming from this angle, only a few examples will be discussed. It should be stressed that these examples should not be seen as representative of all purification problems, in any way.In comparison to the eighties, the latest scientific knowledge about metabolic and toxic interaction, as well as the b i o -ava i l ability of a pharmaceutical active substance have led to greatly changed assessment behaviour. This changed assessment behaviour was not altogether caused by the enormous increase in the performance capability of the analytical procedure, as is so often believed. A variety of different i n fluences and fa c t o rs have helped to cre ate the curre n t assessment scenario.Nowadays when considering the assessment and classification of ecological and economical interaction -chemists are operating at a very different environment than they were in the past decades.In the past decades we have witnessed a restructuration and partly a new orientation of the world markets which have even intensified after the resolution of the East/West economic bl o cks wh i ch we re prev i o u s ly at logge r-h e a d s . This generally positive trend has also caused fundamental changes in the West European market situation.The demand for products at higher and higher degrees of purity and the greater difficulty of the purification problems encountered (such as the resolution of optical isomers) is more and more fo rcing the pharmaceutical industry to use Preparative High Pe r formance Liquid Chromatography (PHPLC). The present contribution discusses briefly the situation of the pharmaceutical industry today and its ch a l e n ge s . With practical examples, it illustrates how PHPLC can compete efficiently with other purification p rocesses like recrystallisation and presents some applications. Examples are also given to illustrate various techniques to make the chromatographic process more rugged and stable.