This study examines the potential of application
of capillary zone electrophoresis (CZE) coupled
to laser-induced fluorescence (LIF) detection involving
derivatization with fluorescamine for the separation and
determination of α-aminocephalosporins in surface water
samples. Via their α-amino group, the non-fluorescent
cefadroxil and cefalexin are capable of forming a highly
fluorescent derivative via their reaction with fluorescamine.
This reaction permits the selective and sensitive detection
of aliphatic primary amines when combined with CE/LIF,
which was achieved with a low-noise diode laser emitting
at a wavelength of 375 nm (Pcw = 5.6 mW) in combination
with a fiber optic-coupled detection cell. Different
types of solid phase extraction cartridges were investigated
to select the optimum solid phase providing maximum
recovery for the studied antibiotics, which were extracted
from spiked Lahn river water samples. Highest recovery
(cefalexin 109.4 ± 3.9 % and cefadroxil 92.6 ± 4.0 %)
was reached with a polymer-based solid phase (Oasis HLB
cartridge), with which a tenfold off-line enrichment was
obtained. On-line enrichment was achieved by sweeping
and large volume sample stacking (LVSS). The high complex
formation constant between the formed derivative and
2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) and the low electric conductivity of the extract after the off-line enrichment
constitute an ideal basis for additional analyte enrichment
by sweeping and LVSS. The enrichment efficiency
obtainable with this on-line enrichment step (after having
filled the complete capillary with the sample solution)
in comparison to field-amplified sample stacking (FASS)
reaches approximately an additional 25-fold improvement.
With the developed method, combining off-line and on-line
enrichment with optimized fluorescence detection, detection
limits as low as 4.9 and 7.5 ng L−1 are obtained for
cefalexin and cefadroxil, respectively, with a starting sample
volume as low as 50 mL. The high repeatability and
accuracy of the proposed strategy permits its application
to the analysis of α-aminocephalosporins in surface water
samples. Its applicability can be extended to other environmental
compartments and other types of primary amino
group containing compounds. In addition, it provides
equivalent sensitivity to other methods using more expensive
equipment like HPLC–MS/MS.