Choosing the Right Flow Rate
Time-resolved SPR responses corresponding to a very
slow flow rate (e.g., 10 µL/min or less) and
a very high flow rate (e.g., 1 mL/min or higher) may
look like the profiles shown on the left and right
of the following figure, respectively. The profile
on the left displays a ‘flat-topped’ peak,
whereas the one on the right shows a sharp profile.
The ‘flat-topped’ profile is more desirable,
since (1) the sample consumption is less and (2) sufficient
time will be given for the binding event to take place
at the surface. Therefore, flow rates less than 100
µL/min are generally used on BI-SPR instruments.
The difference in the profiles is mainly caused by
the dispersion of the sample concentration zone. Dispersion
is affected by three interrelated variables: 1) sample
loop size, 2) length of the tubing between the injector
and the detector, and 3) the flow rate. In the BI-SPR
setup, general applications will lead to the so-called
‘limited-dispersion FI analysis (profile on
the left)’, because the distance between the
valve and the flow cell is short, the flow rate is
slow (microbore tubing), and the sample volume is
much greater than the internal cell volume.
BI-SPR Technology
•
Flow
Injection SPR •
Electrochemical
SPR •
Gas
Phase SPR
