A microfluidic chip formed with multiple fluid channels terminating at a tapered electrospray ionization tip for mass spectrometric analysis. The fluid channels may be formed onto a channel plate that are in fluid communication with corresponding reservoirs. The electrospray tip can be formed along a defined distal portion of the channel plate that can include a single or multiple tapered surfaces. The fluid channels may terminate at an open-tip region of the electrospray tip. A covering plate may substantially enclose most portions of the fluid channels formed on the channel plate except for the open-tip region. Another aspect of the invention provides methods for conducting mass spectrometric analysis of multiple samples flowing through individual fluid channels in a single microfluidic chip that is formed with a tapered electrospray tip having an open-tip region.