Page 389 - Tandem Techniques
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mmol of formic acid was 5 ml/min. A Valco valve (capacity 0.06 ml) was used to inject the sample and
the column was 25 cm long, 0.5 mm I.D. packed with Spherisorb ODS 2. The positive electrospray
spectra of Cypermethrin taken a different cone voltages are shown in Figure 9.32.
Figure 9.32
Positive Ion Electrospray Spectra of
Cypermethrin at Different Cone Voltages
The dependence of fragmentation pattern on cone voltage is similar to that shown by Blanchflower [25]
and emphasizes the importance of using the correct cone voltage for the specific molecules being
examined. The technique worked well, all the solutes of interest were separated and their identity could
be confirmed from their spectra. The technique also proved to be extremely sensitive and for a signal-
to-noise ratio of 3, using the full scan mode, the limit of detection was 120-300 pg. If single ion
monitoring was employed the limit of detection was reduced to 16-60 pg.
In addition to the cone voltage, the size of the droplets formed in electrospray interfaces is extremely
important. Wilm and Mann [28]
