On‐column detection of multiphoton‐excited fluorescence in CE using hyphenated cylindrical‐square capillaries

Abstract

Multiphoton-excited fluorescence (MPEF) is a complementary and useful mode of LIF detection in CE with advantages of ultra-low mass detectability and spectral excitability, but it is currently quite limited by its end-column configuration. In this article, we demonstrate a novel strategy of on-column schemes that can greatly facilitate MPEF detection in CE. FITC-labeled amine species were used as the model samples for the evaluation and comparison of those detection scenarios. By using the square capillary instead of the conventional cylindrical one, the on-column MPEF could be readily achieved, with detection sensitivity of 0.72 microM that was comparable with the end-column mode. However, this strategy unfavorably reduced separation efficiency. The theoretical plate number on averaging all the sample peaks was significantly decreased from 283,000 to 19,000/m. To minimize such an influence, a short square capillary acting as an on-column MPEF detection cell was then mounted to a long cylindrical capillary responsible for the CE separation. Results indicated that both high separation efficiency (240,000/m) and better detectability (0.42 microM) were realized simultaneously by using this binary-capillary configuration. Quantitative analysis was performed under the optimized detector configuration and revealed a linear dynamic range of 2 orders of magnitude, with mass detection limit down to the mid-yottomole level.

Simultaneous separation and detection of cations and anions on a microfluidic device with suppressed electroosmotic flow and a single injection point

“…Finally, the majority of the broadening, 76.3%, occurred in the trapezoidal microchannel, which has been shown to yield lower separation efficiencies than round capillaries in previous studies. [70][71][72][73][74] Although turns can cause significant broadening, 75,76 the broadening from the two turns is low in this device, which is likely a result of the turns opposing each other. In addition, the narrow HDR channels between the turns reduce lateral dispersion.…”

Capillary Electrophoresis

“…Xu et al have demonstrated on capillary multiphoton LIF detection in CE (87). Multiphoton LIF offers low LOD's due to the low background and scattering noise but is difficult to employ in cylindrical CE capillaries.…”