Jcm. Waterval et al., Capillary electrophoretic bioanalysis of therapeutically active peptides with UV and mass spectrometric detection after on-capillary preconcentration, ELECTROPHOR, 22(13), 2001, pp. 2709-2716
An earlier developed capillary electrophoresis, (CE) system with an on-capi
llary adsorptive phase is investigated for its suitability to quantitate lo
w concentrations of angioten-sin II and gonadorelin in plasma. An off-line
solid-phase extraction is used for sample preparation. The on-line preconce
ntration CE system allows multiple capillary volumes of sample solution to
be injected, increasing the concentration sensitivity of CE with 3-4 orders
of magnitude. Furthermore, possible influence of matrix salts can be ruled
out by employing a rinsing step after sample application. Using short-wave
length UV detection, reproducibility and linearity in the low nanomolar ran
ge were satisfactory. The capillary could be efficiently-regenerated using
a programmed between-run rinsing procedure, allowing 20-30 large injections
of sample extracts. Coating of the capillary, improved the robustness of t
he method. Mass spectrometric detection via a previously reported sheathles
s interface increased the selectivity and sensitivity substantially. Recomm
endations are provided for the sample preparation process, the most critica
l part of the system. Further purification of the sample is required to all
ow the loading of larger sample volumes and to optimize the system's robust
ness.