Quadrupole mass spectrometry (QMS) is one of the more ubiquitous mass spectrometric techniques due to its simplicity, speed, cost and robustness. However, as the mass of the transmitted ion is directly proportional to the voltage applied to the quadrupole, the mass range is maximally limited by voltage breakdown occurring between the quadrupole rods. Most commercial systems have a maximum range up to the low tens of thousands m/z, though transmission of higher masses is feasible with a concurrent decrease in resolution. To counteract this problem, it was first proposed in 1955 to scan the operating frequency of the quadrupole while at constant voltage. This would allow higher mass ions to be transmitted without the possibility of voltage breakdown.The frequency scanned quadrupole mass spectrometer (FS-QMS) described in this study utilizes a home-built frequency divider to scan a frequency range of 500 kHz to 500 Hz with very high stability. When coupled with an electrospray ionization source, this instrument theoretically allows for the transmission and resolution of ions in the hundreds of thousands of m/z. Due to the ease with which a lower frequency can be selected (as compared to a higher voltage in conventional quadrupole systems), operation in the third stability region is typically performed. This yields greater resolution than would otherwise be obtained in the first region. Cytochrome c was analyzed and a resolution of approximately 320 was obtained. Cesium iodide clusters were analyzed to determine the working mass range of the instrument.

Frequency scanned quadrupole mass spectrometry for high mass ions

246th National Meeting (2013)

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