Nanoflow gradient generator for capillary high-performance liquid chromatography–nanoelectrospray mass spectrometry

A novel nanoflow gradient generator using a 10-port switching valve with two injection loops installed, which is referred to here as the “Asymptotic-Trace-10-Port-Valve” (AT10PV) nanoGR generator, has been applied to capillary high-performance liquid chromatography (HPLC)–microelectrospray (microESI) or nanoelectrospray (nanoESI) time-of-flight mass spectrometry (TOF MS). In this study, performance of this capillary HPLC-micro/nanoESI-MS system was tested at a flow rate of 200 nl/min by using three typical peptides (angiotensins I, II, and III: 50 fmol each). The result demonstrated that this system provides reasonably good repeatability of peak retention times (R.S.D. of less than 0.5%). Sequential runs of a series of sample injections were performed in the same manner as conventional analysis at microflow rates.