Page 143 - Illustrated Pocket Dictionary of Chromatography

PEAK SKIMMING 143

peak capacity, n The maximum number of peaks that can be ade-
quately resolved (defined by analyst) within a defined time frame is
the peak capacity of the system. When the resolution is taken as unity
(R = 1) the estimation for peak capacity becomes:

[
n ª+ 025 N 12 ¥ ln (1 + k¢ )]
.
1
i
where N is the number of plates for the ith peak and k¢ i is the
capacity factor for the ith peak. Conceptually the peak capacity
can be seen to increase with increasing system efficiency (N, theo-
retical plates) because higher N leads to comparable narrower peak
widths.

peak height, h p The distance, in arbitrary response units (R), of
a peak from its maximum response to the baseline. For a perfectly
nonsloping baseline the line connecting the peak maximum and the
baseline forms a 90° angle to the baseline. For sloping baselines,
the connecting line is drawn between the peak maximum and an
extended line from the nonsloping part of the baseline. See Gaussian
curve.

peak maximum Occurs when the detector response attains its
greatest response for a unique analyte. The retention time is gener-
ated from the peak maximum. A peak “maximum” may also be the
most negative response for an analyte if the detector response can be
positive or negative as in the case of a refractive index detector. See
peak height, h p.
peak purity A mathematical comparison of elution spectra be-
tween a known and a sample. When normalized spectra and overlap
perfectly, then the sample and standard are concluded to be the
same. If not, then multiple points along the spectra are compared and
a purity level determined therefrom.

peak shape The elution profile generated by the detector once the
analyte has passed through the chromatographic system. Statistical
moments and other parameters (asymmetry, width, etc.) are also used
to quantitatively describe the peak shape.

peak skimming A technique used for deconvolving peaks that are
incompletely resolved.