Study on microchip electrophoresis-mass spectrometry

A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was developed using a spray nozzle connected to the exit of the separation channel of a microchip. The developed interface, evaluated using a fluorescent compound and basic drugs, was found to be excellent in terms of the durability and ease of handling. The injection and separation conditions of peptides were examined using tripeptides as test compounds, then the separation of peptide standards and cytochrome c trypsin digests was performed. In the MCE-MS system, suppression of the negative pressure caused by ESI is necessary to improve the separation efficiency. In this study, this was performed by using a microchip with a longer separation channel, by using a high-viscosity background electrolyte. The effect of the separation channel length was significant. The use of successive multiple ionic layers coating of the quartz microchip was performed to stabilize the EOF, even under low-pH conditions. This enabled electrokinetic gated injection under a low-pH condition. Analyses of amino acids and peptides were performed using 50 mM formic acid (pH 2.5) as BGE. The quantitation of creatinine and creatine was performed using arginine as an internal standard. Good linearities were obtained in the sample concentration range of 10 similar to 100 ppm.