H. Watzig et C. Dette, PRECISE QUANTITATIVE CAPILLARY ELECTROPHORESIS - METHODOLOGICAL AND INSTRUMENTAL ASPECTS, Journal of chromatography, 636(1), 1993, pp. 31-38
The separation efficiency of capillary electrophoresis (CE) is said to
be unrivalled by liquid chromatography for a number of applications.
However, the quantitative precision, which is essential for its use in
routine analysis, has been commented upon more critically. The reprod
ucibility of CE is dependent on a number of parameters. The relative s
tandard deviation is predominantly dependent on the absolute sample co
ncentration. Its optimization is very important, and the use of higher
concentrations is found to be more favourable. The problem of the non
-linear relationship between concentration and peak data, caused by co
lumn overload, is less critical. The buffer concentrations are adjuste
d to the optimum sample concentrations. Validated buffer recipes and r
insing steps will lead to more stable conditions, and the trends that
occur can be diminished by the stepwise use of an external standard. M
uch of the precision is dependent on instrumental aspects. Seven set-u
ps from different manufacturers were tested. Thermostating proved to b
e the most important parameter in achieving a reproducible dosage. Ion
mobility and buffer viscosity are controlled by the temperature. Thes
e parameters influence the amount of sample that is injected by electr
okinetic or hydrodynamic injection. The recording of temperature, curr
ent, voltage and power is necessary for proper documentation. Short ca
pillaries should be usable for achieving a short analysis time and thu
s a large number of repetitions per unit time, which is important for
statistical certainty.