Precipitation high throughput preparation

In real life, sample preparation techniques are utilized in tandem with HPLC/MS/MS. Due to the high selectivity of LC/MS/MS in the SRM mode, small quantities of impurities or interferences in the purified fractions from sample preparation protocols dealing with biological matrices can be tolerated. This is especially true for protein precipitation, which is widely used because of simplicity and rapidity, when high-throughput turn-around is required. High-throughput HPLC is discussed elsewhere in this book. 

A 63-membered library of pyrazoloquinazolinones was prepared from nine hydrazinobenzoic acids and seven cyanoketones [71] in a microwave-assisted tandem a-aminopyrazole formation—an amide bond-forming ring closure reaction. In many cases, the products precipitated out of the reaction mixture and simple washing with diethyl ether furnished the products with purities greater than 95%. Alternatively, heterocycles were isolated in a high-throughput fashion via preparative HPLC (Scheme 24). 

Bevan introduced a high-throughput alteration of the method. He uses 10 mM DMSO stock solutions for a precipitation assay. In many biological assays 10 mM DMSO stock solutions are the standard stock solution, from which aliquots are added to the various assays. 10 mM DMSO stock solutions are readily available and the sample preparation can be minimized. 

Many different sample preparation techniques are available to the drug discovery scientist. Off-line sample preparation procedures include protein precipitation, filtration, dilution followed by injection, liquid-liquid extraction (LLE), and solid-phase extraction (SPE). Typically, these procedures are performed in an automated, high-throughput mode that features a 96-well plate format. Online sample preparation procedures include SPE and turbulent flow chromatography (TFC) with conventional chromatographic media or restricted access media (RAM). These online approaches are often simple and easy to automate. 

Soluble linear polystyrene can also be used to prepare recyclable sulfoxide reagents for Swern oxidations [104]. While the styrene copolymer sulfoxides 68 are not strictly catalysts, they are easily recycled by precipitation with cold methanol. Reoxidation of the sulfide with f-BuOOH reformed the starting polymeric sulfoxide 68. While some decrease in yield was seen from cycle to cycle through four cycles, the products were not contaminated with polymer - an advantage in high throughput chemistry where separations need to be as simple as possible. 

The main difference from academic catalyst preparation is that in industry only a limited number of unit operations are used and therefore, several highly sophisticated lab preparation techniques, unless they result in extraordinary catalysts, cannot be applied in industry. Moreover, economic factors (costs of precursor materials) and ecological demands (avoid toxic and environmentally harmful waste) have to be considered. In fact, most catalysts in industry are manufactured by impregnation, precipitation, or ion-exchange techniques. Recently, Degussa has published some features of their high-throughput synthesis equipment illustrated by preparation of an advanced Pd-based vinyl acetate catalysts [109,118). 

Thin layers on microtiter plate wells The microtiter plate format is universally employed in biological immunoassays such as ELISA and enables a very high assay throughput, in particular when combined with automation. Thus, thin layers ofMIPs in microtiter plate wells are of immense interest for MIAs involving colorimetric or fluorescence detection. Two approaches have been described the entrapment of 2,4-D-imprinted vinylpyridine/TRIM microspheres in films of polyvinylalcohol hydrogel [53] and the preparation of imprinted poly-3-aminophenylboronic acid and related conjugated polymers which precipitate as films on the microwell surface [19,54]. The polyvinyl alcohol composite films have been used in combination with... 

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