Page 41 - Illustrated Pocket Dictionary of Chromatography

36 COATING EFFICIENCY

a coated support, the appropriate liquid stationary phase is dissolved
in a volatile solvent and then slurried with the support material. The
solvent is then slowly evaporated from the slurry, thereby depositing
the stationary phase on the solid support material.

coating efficiency The calculation for coating efficiency is used
to estimate how closely the performance of a GC column approaches
its theoretical limit:
H
% coating efficiency = (H min actual ) ¥ 100
where H min and H actual are the height equivalent to a theoretical plate
and the actual theoretical plate minimum, respectively.

coefficient of determination, r 2 The coefficient of determina-
tion is a mathematical determination of how strongly a dependent
2
variable is correlated to the independent variable. The value r is cal-
culated from the square of the correlation coefficient, r. Perfectly cor-
2
related data have an r (or r) value of 1.0 or -1.0. For many methods
in which detector response and concentration are expected to have a
2
linear correlation, minimum acceptable r values are typically >0.95.
coelution A condition in which two or more peaks are not base-
line resolved from one another. The resolution factor is a mathemat-
ical representation of how well peaks are resolved.

cold trapping The process of cold trapping, that is, holding the
column temperature at least 100°C below the boiling point of the
lowest boiling component of a sample, is used to condense and con-
centrate the sample into a very narrow band on the GC column.
Elution is then accomplished by raising the column temperature.

column bank A term used in size exclusion chromatographic
separations when more than one column is connected in series in
order to generate sufficient molecular weight discrimination.
column efficiency A measure of the overall performance of a
column with respect to peak shape, retentivity, resolution, and speed.
In a very general way, a column is considered more efficient if it gen-
erates more theoretical plates, a more symmetric peak and can
resolve many analytes in a short period of time.

column length, L The distance from the column inlet to its outlet
that contains stationary phase.