Single stage screen

Laboratory Exercise Efficiency of Separation on Single-Stage Screening... 

There are three major types of screen designs the single stage, sequential, and tiered. Both the sequential and tiered are multistage approaches, and each of these types also varies in terms of how many parameters are measured. But these three major types can be considered as having the following characteristics. 

For purposes of our discussion here, we will primarily focus on the single-stage system, which is the simplest. The approaches presented here are appropriate for use in any of these screening systems, although establishment of activity criteria becomes more complicated in successive screens. Clearly, the use of multistage screens presents an opportunity to obtain increased benefits from the use of earlier (lower-order) screening data to modify subsequent screen performance and the activity criterion. 

Fig. 5.5 On-line HPLC bioactivity screening of a mixture of five flavonoids spiked with two cathepsin B inhibitors, E-64 and leupeptin using acetylcholinesterase as biological target. MS instrument Shimadzu LCMS-2010 single-stage quadrupole mass spectrometer, (a) TIC chromatogram of the mixture, scan range m/z 75-750 (b) mass chromatogram of AMC (m/z 176) (c) mass...

A combination of two tests is clearly better than one, but at this early stage, when there is still more chemical development likely, one is probably enough. Given that in silico methods are most effective in the identification or designing out of Ames positive compounds, a single eukaryotic screening test would probably be optimum. 

LC/MS is an important addition to the techniques used routinely to analyze unknown samples. It is not a substitute for other techniques but is complementary, for example, to GC/MS, GC/FTIR, and NMR. In OPCW proficiency tests, a number of laboratories use single-stage LC/MS as a rapid screening procedure for water samples and aqueous extracts of matrices such as soil, and GC/FPD or... 

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