Introduction:
The Agilent 6560 Ion Mobility Quadrupole Time-of-Flight (IM-QTOF) LC/MS system enables high performance ion mobility and very precise and accurate collision cross section (CCS or W) measurements without class dependent calibration standards. The Agilent mobility device operates under uniform low field conditions, thus allowing the drift time information for ions to be directly converted to collision cross section information. The innovative ion funnel technology in this instrument dramatically increases the ion sampling into the mass spectrometer and results in higher quality MS/MS spectra at trace levels. The Agilent IM-QTOF system is the first commercially available uniform field ion mobility system, which coupled with the Agilent 1290 UHPLC, provides the combined separation power and selectivity of LC, IM, and MS techniques. Laboratories involved in cutting edge research can speed up research programs and have greater confidence in compound identification with the additional dimension of separation as well as the structural information provided by ion mobility measurements. This instrument is the only commercially available drift tube ion mobility high resolution (both mobility and mass) LC/MS system that simultaneously provides high sensitivity and accurate collision cross section measurements.
The Agilent ion mobility system was developed with the collaboration of scientists from a number of academic institutions and government laboratories. In multiple studies, the instrument has demonstrated the ability to reveal significantly greater analytical detail for complex samples compared to high resolution mass spectrometry technology alone. Researchers have reported that while high resolution mass spectrometry has become the analytical cornerstone for proteomics, metabolomics, and other research applications requiring the analysis of highly complex samples, there has also been significant interest in the use of ultra-fast orthogonal techniques to provide added dimensions of separation. This new ion mobility system will provide researchers with greater analytical detail than ever before.
Principles of Ion Mobility Separation In a classical uniform field drift tube, the electric field within the drift cell moves ions through the device while the drag force due to the collisions of these ions with the stationary buffer gas molecules acts against the electrical force that moves the ions. The drag force experienced by the ions depends on their collision cross sections (a function of size and shape), electrical charge, and mass. Multiply charged ions move through the buffer gas more effectively than singly charged ones since they experience a greater force due to the electric field. Ions with larger cross sections are retarded more easily by collisions with the buffer gas in the drift tube. The drag force resulting from collisions of ions with the buffer gas molecules acts against their acceleration imposed by the electric field. Thus an equilibrium state is quickly reached and the ions start moving with constant velocity (Vd) which is proportional to the applied electric field (E). The proportionality constant (K) is the gas phase mobility of an ion. The diffusion limited resolving power is dependent upon the length (L) of the drift cell, electric field (E), charge state of the analyte ions (Q), and the buffer gas temperature (T).
Vd = KE
Mobility is a function of the ion’s interaction with the buffer gas, its mass and its electrical charge. Furthermore, the reduced mobility (K0) depends on the gas temperature and the mass of the buffer gas molecules.
K0 = L t d E P 760 T 273.2
where L is the length of the drift cell, t d is the corrected drift time, E is the electric field across the drift cell, P is the pressure of the drift cell, and T is the temperature of the buffer gas
You must be logged in to post a comment.