Sample preparation general considerations

Before injecting the first sample some general considerations have to be taken into account with regard to the design of the preparative chromatographic plant. All preparative HPLC plants consist, basically, of the same components (Fig. 5.1) a solvent and sample delivery system, the preparative column and a detection and fraction collection system. 

The sample preparation in LC analysis is as important as the chromatographic separation itself. The procedure will often require considerable skill copied with a basic understanding of chromatographic methodology. The analyst will need to have some familiarity with micro techniques including general micro-manipulation, microfiltration, centrifugation and derivatization. 

In general, new sample preparation technologies are faster, more efficient and cost effective than traditional sample preparation techniques. They are also safer, more easily automated, use smaller amounts of sample and less organic solvent, provide better target analyte recovery with enhanced precision and accuracy. Attention to the sample preparation steps has also become an important consideration in reducing contamination. A useful general guide to sample preparation has been published [3]. A recent review on sample preparation methods for polymer/additive analysis is also available [4]. 

Microprocessors, computers and robots are in themselves only subsets of the general field of automation. When the journal of Automatic Chemistry was launched in 1979, one of my fellow founders, Professor Howard Malmstadt, suggested that it would be many years before the journal would be understood in the USA. This, he believed, was because the term computing was generally considered synonymous with automation . The reahty that sample preparation was often the major bottleneck in analysis was ignored. More recently, robotics have found considerable favour, and, again, the term automation has been confused to refer to robotics and nothing else. 

Very few papers have been published in the last 10 years related to vitamin D determination in food. Thereby, for general consideration about sample preparation the book chapter published by Nolle et al. [407] was used as reference. 

Abstract NMR spectroscopy is so far the only analytical technique that has been used to get a detailed structural characterization of hydrogenated fullerenes. A substantial amount of information derived from different NMR experiments can thus be found in the literature for a number of fullerenes hydrogenated to various degrees. These studies have benefitted from the fact that chemical shifts of II and 13C and in some cases also 3He can be used to obtain structural information of these compounds. Such results, together with discussions about different NMR experiments and general considerations regarding sample preparations, are summarized in this chapter. The unique information, both structural and physicochemical, that can be derived from different NMR experiments ensures that this technique will continue to be of central importance in characterization of hydrogenated fullerenes. 

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