Page 144 - Illustrated Pocket Dictionary of Chromatography

144 PEAK VARIANCE, s 2

When there is overlap between peaks a number of techniques are used to estimate
the separate areas of the peaks. Peak skimming uses an exponential curve from
the largest peak through the smaller peak. A valley-to-baseline method drops a line
that is perpendicular to the baseline from the valley between the two peaks.

2
s
peak variance, s A direct statistical measure of peak width (i.e.,
second moment) for Gaussian peaks.
peak width, w A measure of how long it takes for the analyte
profile to pass through the detector. See Gaussian curve. The peak
width is an important parameter because it is used to determine
column efficiency (theoretical plates, N), resolution (R s ), etc. For
nonsymmetrical peaks, the peak width is determined by direct
measurement.
PEEK Polyetheretherketone. PEEK is a polymer that has become
frequently used in systems where stainless steel causes problems
(e.g., metal ion analysis and some protein/peptide analyses). Con-
necting tubing, injector loops, and even column tubing are now
fabricated from PEEK.