Biomedical Engineering – From Theory to Applications

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Biomedical Engineering – From Theory to Applications
the reproducibility of cutting and also overall analysis is generally lower than in the
hydrodynamically closed CE systems due to the fluctuations of the non selective flows in
the separation system.
Fig. 4. Schematic representation of the ITP–CEC set-up. Right scheme: Schematic
representation of the ITP–CEC–UV set-up with a (P) programmable capillary injection
system, (D) UV–VIS absorbance detector, (A) amperometer and (T) laboratory made
polyethylene T-piece. Untreated fused-silica capillaries of 220 m I.D. (1 and 2) and 75 m
(3) are used. Left scheme: Schematic representation of the entire ITP–CEC–MS set-up. The
electrospray needle with the sheath flow contains the CEC column, which is directly
connected with the electrospray. The spray is directed towards the inlet capillary of the
interface on the SSQ 710 mass spectrometer (MS). HV is the electrospray power supply.
Reprinted from ref. (Mazereeuw et al., 2000), with permission.
The first ITP stage of the ITP-CEC combination can apply all benefits as they are described
generally for the ITP stage of ITP-CZE combination in section 3.1.1.1. In ITP-CEC, the ITP
sample clean-up effect is extremely important for enhancing reproducibility of CEC
especially when injecting complex biological samples. The CEC stage of the ITP-CEC
technique can take a high advantage of the hyphenation with the UV-VIS or MS detection,
for the schemes of the experimental setups see Fig. 4. It is pronounced in the situations when
the selectors interfering with the detection must be used in the separation system in order to
establish the required selectivity. Immobilization of such selectors in the CEC column
prevents their entering into the detector cell resulting in the elimination of the detection
interferences. In this way, the maximum response of the UV-VIS or MS detector can be
obtained for the analyte. Hence, the ITP-CEC combination seems to be a powerful tool for
the on-line selective separation, sensitive determination and spectral identification of chiral
compounds and various other isomers and structurally related compounds (i.e.
“problematic” analytes) present in complex ionic matrices. The ITP-CEC-MS hyphenation
seems to be one of the most promissing methods for the fully automatized biomedical chiral
analyses such as enantioselective pharmacokinetic studies, metabolomics, etc. (Mazereeuw
et al., 2000).