Injection of fluorescently labeled analytes into microfabricated chips using optically gated electrophoresis

Optically gated electrophoresis has been used as an alternative method of sample introduction in microfabricated chips. Utilization of this injection technique permits rapid serial sampling and consumes less chip space than traditional chip-based injection methods. 4-Chloro-7-nitrobenzofurazan (NBD)-labeled amino acids have been injected in microfabricated chips using optical gating and have yielded results comparable to the T-type injection methods currently used. Picoliter-size injection volumes have been reproducibly introduced with less than 3% deviation in retention time and peak area. Six consecutive separations have been accomplished in under 30 s using a separation length of 1.1 cm. Plate heights from this analysis range from 4.5 to 0.8 μm. The combination of rapid successive injections and reproducible separations demonstrates the utility of this method in analyzing rapid dynamic events such as on-line sampling or monitoring chemical processes.