Page 159 - Illustrated Pocket Dictionary of Chromatography

Q

quadrupole mass analyzer A quadrupole is constructed from
four hyperbolic rods set at precisely determined right angles to one
another. A DC voltage (+ or -) is applied to alternating rods and
rapidly alternated. A radio frequency (rf) is applied along the rods as
well. By adjusting the DC voltage and the rf signal, various mass-to-
charge ratios (m/z) are passed through the quadrupole and strike the
detector.
j A measure of the fraction of excited mol-
quantum efficiency, j f
ecules that will fluoresce:

j f = k f (k f + k i )
where k f is the rate constant for the fluorescence process and k i rep-
resents the rate constant for all competing radiative pathways.
quaternary alkyl amine A quaternary amine has the following
general structure:

CH 3
CH 3 N CH 3 Br
CH 3
Tetramethylammonium bromid
quaternary amine

The methyl form (R = R¢= R≤= methyl) is grafted to a support and is
a common form for strong anion exchange sites. Hydroxide salts of
free compounds, for example, tetrabutylammonium hydroxide, are
used as ion-pair reagents.

Illustrated Pocket Dictionary of Chromatography, by Paul C. Sadek.
ISBN 0-471-20021-2 Copyright © 2004 John Wiley & Sons, Inc.
159