An ultrashort-duration, high-repetition-rate pulse source for laser ionization/mass spectrometry.

This paper describes a sample inlet system with several advantages over other pulsed valves, as applied to resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry. The nozzle is based on online concentration by analyte adsorption/laser desorption (online COLD), where a capillary column with a narrowly synthesized tip is employed for sample introduction. The analyte molecules adsorbed at the tip are desorbed by a pulsed laser and are injected into a mass spectrometer as a packet. The online COLD nozzle can produce very short gas pulses on the order of 1 μs. Moreover, this nozzle is capable of operating over a wide range of repetition rates from 1 Hz to 1 kHz. In addition, this nozzle intrinsically possesses several unique characteristics; for instance, it can be heated to very high temperatures and has nearly zero dead volume. Therefore, the present sample introduction technique offers an ideal and versatile nozzle for laser ionization/mass spectrometry.