Page 404 - Tandem Techniques
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desorbing the materials from the affinity column and re-adsorbing them on the trap.
Figure 9.44
Diagram of the Sampling Arrangement for the Analysis of LSD
in Urine by an LC/MS Tandem Employing an Electrospray Interface
The trap was then back-flushed, and the desorbed materials eluted through the LC column, through an
API interface and into the mass spectrometer. Four metabolic productions in addition to the unchanged
LSD itself were separated and identified from their mass spectra. The original measured concentration
of LSD in the urine was 0.9 ng/ml. These results demonstrated the very high sensitivity that could be
obtained by utilizing the selective extraction, that can be provided by affinity chromatography.
