Quantitative Bioanalysis—Automated On-Line Extraction

In response to off-line SPE assays in the 96-well plate format, LC/MS analyses that feature the direct injection of plasma with on-line extraction have been reported (Ayrton et al., 1997 Needham et al., 1998). This quantitative process approach eliminates the time- 

TABLE 6.18 Comparison in consumable costs between disk cartridge and 96-well plate for every 100 samples 2 

Source. Reprinted with permission from Simpson et al., 

With this on-line automated method, more than 250 samples have been analyzed unattended in a 24 h period. Good results are obtained over a 10-1000 ng/mL range. The LOQ and LOD are 190pg and 58pg, respectively. Accuracy and precision values are 9.0% or better over the entire range of the assay. 

Sample preparation issues inherent with on-line extraction techniques that deal with the addition of triethylamine to the mobile phase and the calculation of extraction recovery are likely to be addressed for future applications however, this method appears to 

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