M. Dankova et al., Capillary zone electrophoresis of orotic acid in urine with on-line isotachophoresis sample pretreatment and diode array detection, J CHROMAT A, 916(1-2), 2001, pp. 143-153
Potentialities of capillary zone electrophoresis with on-line isotachophore
sis sample pretreatment and diode array detection (ITP-CZE-DAD) to the sepa
ration, detection and identification of trace analytes present in biologica
l matrices were investigated. Urine represented a multicomponent, variable
and high ionic strength matrix while erotic acid was chosen as a model anal
yte of a practical clinical relevance in this investigation. Using the ITP-
CZE combination in the column-coupling configuration of the. separation sys
tem ITP provided an enhanced sample load capacity to the separation system
(a 30 mul sample injection volume), concentrated the analyte and served as
an on-line sample clean up technique. On the other hand, CZE performed a fi
nal separation of the analyte from matrix constituents present in the ITP p
retreated sample and provided favorable conditions for its detection and id
entification by DAD. using current correction and smoothing procedures anal
ytically relevant DAD spectra of erotic acid could be obtained also in inst
ances when this was injected in a model sample at a 2 . 10(-7) mol/l concen
tration (an estimated limit of determination of erotic acid at a 218 mm det
ection wavelength). ITP-CZE separations of urine samples (based on differen
ces in acid-base properties and host-guest complexations of the analyte and
matrix anionic constituents) led to significant sample clean ups. Conseque
ntly, DAD spectra of erotic acid matching its reference spectrum, could be
acquired also in instances when the acid was present in urine matrices (loa
ded in 30 mul injection volumes of 20-fold diluted urine samples) at 4-6 .
10(-7) mol/l concentrations. Here, residual trace matrix interferents preve
nted a closer approach to the above value attainable for model samples. Alt
hough this work was focused only on one analyte: and urine matrix it implie
s very promising potentialities of the ITP-CZE-DAD combination in the ident
ification and quantitation of trace analytes present in biological matrices
, in general. (C) 2001 Elsevier Science BN. All rights reserved.