Page 62 - Illustrated Pocket Dictionary of Chromatography

DRIFT TUBE 57

-
2-
have three forms, H 2 A, HA , and A , when in solution. As a conse-
quence, a value for D can be developed as:
-
2-
D = [ H A B ] ( [ H A A ] +[ HA ] +[ A ] )
2
2
A
A
distributor, distributor plate A thin stainless steel disk that is
placed between the inlet column endfitting and the inlet frit. The star
pattern in the distributor is to facilitate the spreading of the sample
over a wider area of the inlet frit and hence the column.

Two sets of frits-distributors are shown with the distributor on the right. Note
the “star-like” pattern that runs from the center to the edge of the distributor. This
provides an channel of little of no resistance to flow and allows the sample to
spread across the top of the column packing.

double peak Systems that are grossly contaminated or have
severely compromised packing beds can generate a split or double
peak.
drift The average slope of the detector baseline over the course of
an analysis; can be caused by incomplete column equilibration,
changes in temperature of mobile-phase composition, system leaks,
and contamination of the sample or mobile phase.
drift tube A component of an evaporative light scattering detector
that evaporates the mobile-phase from the analyte before it enters the
light-scattering cell. The drift tube operating temperature must be
optimized for both the mobile-phase composition and the flow rate in
order for the detector to generate reproducible results.