Effect of reverse scan on mass measurement accuracy in an ion trap mass spectrometer

✍ Scribed by Francesco L. Brancia; Roger Giles; Li Ding

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 93 KB
• Volume: 39
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.604

✦ Synopsis

Effect of reverse scan on mass measurement accuracy in an ion trap mass spectrometer

Quadrupole ion trap mass spectrometers have become widely popular mass analysers for the structural determination of gaseous ions generated under various ionization conditions. 1 -3 Although the instruments possess attomole-level sensitivity, good resolution, 4 together with the possibility of performing multi-stage mass spectrometry, 5 mass measurement accuracy is still not comparable to that obtained in other mass analysers. The poor mass accuracy observed is due to two main influences caused by the intrinsic chemical properties of the analyte (chemical shift) and the sensitivity of ion secular frequency to the charge density of the ion cloud (space charge shift). The chemical shift effect was partially solved by increasing the distance between the two end-caps by 10.7%. 6 Such observed displacements are attributable to dipole moment of the ion, 7,8 its propensity to fragment 9,10 and localization of the functional groups. 11 Separate from the chemical shift is the space charge shift, which results from ion-ion interactions among species of same polarity (i.e. space charge effects). This phenomenon also restricts the mass accuracy of ion traps. The charge density is produced by (i) the total number present in the trap, (ii) the total number of ions at a specific value of m/z and the abundances