Page 510 - Tandem Techniques

Page 496

From the point of view of the analyst, it is seen that the actual concentration sensitivity in terms of
modern instrumentation is relatively poor. However, due to the very small volumes involved, the actual
mass sensitivity is commensurate with that of other modern detection methods.

Figure 13.9
The Basic Tandem Instrument Incorporating
the Time of Flight Mass Spectrometer

The general arrangement of the apparatus is shown in Figure 13.9. It consisted mainly of three sections,
the usual high-voltage electrophoresis power supply, the buffer reservoir, fused quartz capillary conduit
and electrospray injection system, and finally the mass spectrometer. The time of flight mass
spectrometer was that manufactured by R. M. Jordan and Co. The details of the interface are shown in
Figure 13.10.

The fused quartz capillaries were 110 to 120 cm long, 200 µm O.D., and 100 µm I.D., and the running
buffer was composed of a 50 mM solution of acetic acid in 50/50 methanol water mixture, having a pH
of approximately 4.0. The electrospray unit was a modified form of that manufactured by Analytica
Inc., the fused quartz capillary replacing the stainless steel needle of the original device. A thin gold
wire, 25 µm in diameter, was inserted about 2 mm into the exit orifice of the quartz