A miniaturized transverse flow gating interface for the on-line coupling of solid-phase extraction with capillary electrophoresis.

A miniaturized transverse flow gating interface (μ-TFGI) is presented for the on-line coupling of solid-phase extraction with capillary electrophoresis (SPE-CE). The fabrication and operation procedures of the μ-TFGI are described in detail. After the operation conditions were investigated and selected, the μ-TFGI was evaluated on an SPE-CE-UV setup using clenbuterol (CLB) as the test analyte. The preconcentration factors obtained with the SPE-CE-UV system and the SPE-UV part were 600 and 620, respectively. The plate numbers obtained within 3 min were 100000 and 80000 for automatic injection via the μ-TFGI and manual direct injection, respectively. The precisions were 2.4 - 6.8% (RSD, %, n = 9) and 3.1% (RSD, %, n = 27) for the recovery (94.3 - 101.9%) and migration time of CLB spiked in urine samples, respectively. These results demonstrate that the μ-TFGI has the ability to exactly and reproducibly transfer nanoliters of fractions from SPE onto CE with no degradation of the efficiencies of SPE and CE.