Pittcon 2013 - Miniature Mass Spectrometers - Abstract 6
This session was recorded during Pittcon 2013 in Philadelphia, Pennsylvania on Monday, March 18, 2013.
TITLE: A Portable VUV Photo-Ionization Digital Ion Trap Mass Spectrometer for VOC Inspection
AUTHOR: Li Ding - Kunshan Hexin Mass Spectrometry Co Ltd
ABSTRACT OVERVIEW: The digital ion trap driving method has recently combined with the linear ion trap analyzer fabricated with printed circuit technology. Such a mass analyzer features high throughput, high sensitivity, light weight and lower production cost and is now considered suitable for portable instrument for VOC inspection. The gases sample is sucked into the membrane cell directly using a fish pump and the heated membrane has another surface facing the photo ionization source. The selectivity of the membrane and 10.4 eV photo ionization allows sufficient suppression to ambient background before tandem mass analysis achieved by the high capacity linear ion trap. The trap is made of four ceramic printed circuit boards partially processed with the microchip technology. Helium is used as the buffer gas for ion cooling and collision induced dissociation in the ion trap. Without using pressure regulator with the gas cylinder, a pulse valve with controlled duty cycle and a feed-back algorithm has been used for regulate the He gas pressure in ion trap chamber directly. Digital square wave voltage at 100 or 250V 0-p is used for operating the digital linear trap and digital dipole excitation is also used for ion ejection and CID. The voltages used together with the frequency scanned square waveform allow a mass range from 28 to 800 amu covering major environmental sample species. Scan rate at 10 to 50 scans per sec was used for on line monitoring.
The designed portable mass spectrometer has its total weight including battery, flat panel computer, gas cylinder and the heavy-duty cases about 17kg and can continually work up to 2 hours without main supply. Mass resolving power was measured at Toluene mass of 91 Th and peak width of 0.35 FWHM was obtained. Xylene standard gas diluted to 50 ppb was used for sensitivity test and signal to noise ratio over 10 was achievable after 256 scans averaging (within 30 sec).