Drop-by-drop chemical reaction and sample introduction for capillary electrophoresis.
In this paper, we report a novel sample introduction and chemical reaction strategy by drop-by-drop inkjet injection for an electrophoretically mediated microanalysis (EMMA). This method makes it possible to achieve an on-line introduction of reactant solutions by alternately ejecting small plugs, with an overlapping region of the plugs for mixing the reactants by electrophoresis, supporting chemical reactions, followed by electrophoretic separation of the final compounds. As a proof-of-concept of the method, the EMMA of an inkjetted mixture of 4-fluoro-7-nitrobenzofurazan (NBD-F) and amino acids was carried out as a model chemical reaction. The product NBD-amino acids were quantified by detection with laser induced fluorescence. The optimal conditions for the procedure were: inkjet driving voltage: +40-44 V; pulse width: 20-24 μs; drop-by-drop injection of reactant solutions: alternately 2 drops × 25 times for the amino acid solution and the NBD-F solution; zone overlapping voltage and time: 3 kV and 2 s; incubation time after overlapping: 5 min; separation voltage: 18 kV. Under the optimized conditions, a significant enhancement in sensitivity and a sensitive quantitative analysis were realized. The results obtained were comparable with those using the off-line labeling method. This method is rapid, cost-effective, and readily automated for EMMA.
Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo, Metropolitan University, Minamiohsawa, Hachioji, Tokyo 192-0397, Japan. uchiyama-katsumi@tmu.ac.jp.
Fengming
F
Chen
Ying
Y
Rang
Ying
Y
Weng
Luyao
L
Lin
Hulie
H
Zeng
Hizuru
H
Nakajim
Jin-Ming
JM
Lin
Katsumi
K
Uchiyama
D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000737:chemistry / Q000302:isolation & purification; D000596:Amino Acids / Q000737:chemistry / Q000302:isolation & purification; D019075:Electrophoresis, Capillary / Q000295:instrumentation / Q000379:methods*; D007267:Injections; D046208:Microchip Analytical Procedures; D013997:Time Factors
D000596:Amino Acids; C032930:7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole; D009327:4-Chloro-7-nitrobenzofurazan