Solid-phase extraction benefits

Product extraction from large volumes of fermentation broth can be complex, requiring large volumes of organic solvent or solid-phase extraction techniques, which can sometimes greatly reduce or even cancel out the benefits of the biotransformation itself, such as shorter route and environmentally benign conditions. 

Fig. 13.9 The benefits of strong cation exchange (SCX), solid phase extraction (SPE) clean-up of samples. The reversed phase HPLC-ESI-MS base ion (m/z 200-500) chromatograms of a reduced (zinc/sulfuric acid) extract of Senecio ovatus. (a) Methanolic solubles of the reduced extract and, (b) the SCX SPE of the methanolic solubles of the reduced extract.

All sample types are amenable to SPE with suitable handling solids, liquids, semisolids, etc. Solid-phase extraction is extensively used in sample preparation, as it offers a fast, safe, and convenient means for subsequent analysis by chromatographic techniques [HPLC, thin-layer chromatography (TLC), GC, etc.]. The major benefit is that it requires less solvent than conventional LLE methods. Impurities are removed and the analytes are... 

Further improvement of throughput in LC-MS analysis may be achieved by step-gradient elution. This elution format is essentially an on-line solid-phase extraction (SPE) process, where the samples are loaded onto the column, washed with aqueous mobile phase to remove water soluble impurities, and compounds are eluted with a mobile phase of high organic content. The technique combines the simplicity of FIA with the benefit of the removal of impurities and buffer components before mass spectrometry detection. In this case, selectivity is achieved by mass spectrometry alone without chromatographic separation. The technique has been used for compound purity assessment and quantitation. An on-line back-flush SPE-MS technique has been used by Marshall for quality assessment of the combinatorial libraries [112]. This back-flush elution procedure provides a very effective in-line removal method... 

Online solid-phase extraction Same benefits as solid—liquid extraction but also automated Same disadvantages as solid—liquid extraction but also requires dedicated and expensive instrumentation LC—MS/MS determination of indacaterol in serum [6]... 

Capillary electrophoresis can be applied to nonionics if they are first made ionic by derivatization with, for example, phthalic anhydride (11,15). This has the additional benefit of making them detectable by UV absorbance. Excess derivatizing reagent results in a few minutes of unusable time at the beginning of the electropherogram as the reagent passes the detector. This is minimized if the excess reagent is removed by dialysis or solid phase extraction (16). 

Also, subcritical (hot/liquid) water can be used as a mobile phase for packed-column RPLC with solute detection by means of FID [942]. In the multidimensional on-line PHWE-LC-GC-FTD/MS scheme, the solid sample is extracted with hot pressurised water (without the need for sample pretreatment), and the analytes are trapped in a solid-phase trap [943]. The trap is eluted with a nitrogen flow, and the analytes are carried on to a LC column for cleanup, and separated on a GC column using the on-column interface. The closed PHWE-LC-GC system is suitable for many kinds of sample matrices and analytes. The main benefit of the system is that the concentration step is highly efficient, so that the sensitivity is about 800 times better than that obtained with traditional methods [944]. Because small sample amounts are required (10 mg), special attention has to be paid to the homogeneity of the sample. The system is... 

The ability to miniaturize DNA extraction and analysis devices will benefit many research areas which require portable and rapid analysis of biological samples. Some of these areas are those where only a small DNA sample such as samples from only a few cells must be efficiently detected such as is commonly encountered in forensic analysis at crime scenes or is necessary for biological warfare monitoring. Miniaturized DNA analysis can also be adapted to replace conventional DNA extraction techniques. There is a huge reduction in the quantity of reagents which are used and the small size naturally lends itself to mass production and automation that will reduce the cost per device and analysis time. Approaches toward miniaturizing both solid-phase and hquid-phase extraction techniques are discussed in the next section. 

Solid-phase microextraction (SPME) appears to offer flavor and fragrance chemists significant benefits as an extraction/concentration technique prior to gas chromatography (GC) analysis. It is simple, rapid, solventless, and sensitive. Furthermore, it is less expensive to implement than purge-and-trap methods and many other sample preparation techniques that require specialized ancillary instrumentation. Before adapting a new extraction technology like SPME as a routine procedure, it is important to understand how it compares to the standard sample preparation techniques that have been used in the past. 

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