PURPOSE: To feed stable sample ions to a mass spectrometer by constantly maintaining at a set value an electric field generated between a probe and a first pore without being affected by changes in the amount of samples flowing out of a liquid chromatograph.
CONSTITUTION: Voltages applied to a probe 4 and a first pore 6 are Va and Vb, respectively, and Va-Vb is calculated by an adjusting means 13. At the means 13 a setting signal voltage of a power source 5 for the probe is preset to a state in which a high electric field between the probe 4 and the pore 6 can continuously ionize samples. Therefore when the flow rate of the samples from a liquid chromatograph 1 to the probe 4 is varied the voltage Va is varied and the value of Va-Vb is also varied. However, since the means 13 is set at a voltage value at which the samples can be continuously ionized, the samples are stably ionized even with changes in the flow rate. Stable sample ions can thus be fed to a mass spectrometer.
MATSUMURA KAZUMI