High resolution Varying Field Drift Tube Ion Mobility Spectrometer with diffusion autocorrection

Enhancing Separation and Constriction of Ion Mobility Distributions in Drift Tubes at Atmospheric Pressure Using Varying Fields

“…In a previous work describing the VFDT, the Nernst–Planck equation was solved for the linear region. , In it we assumed that a linearly decreasing field E = A ( L E – z ) was present, where A is the slope of the field and L E > L is the distance at which the field would become zero, being L the length of the drift region. The derivation of the ion distribution has been added to the Supporting Information.…”

“…The derivation of the ion distribution has been added to the Supporting Information. The spatial resolving power for the linear varying field portion of the system was given as Here q is the charge, E max = AL E is the maximum electric field at the beginning of the linear field region, K is the mobility of the ion of interest, t is the arrival time, k b is the Boltzmann constant, T is the temperature, and −∞ < c zσ ≤ 1 is a constant so that is the square of the standard deviation of the initial distribution. , The overall spatial resolving power is significantly higher than that of a constant electric field DT and spatial resolving powers over 200 under regular operation were expected theoretically . The experimental results did show a slightly higher resolving power than that of the regular DT, but not as high as expected.…”

“…Nonconstant fields may be used to correct diffusion in the axial direction, and there is almost no limitation on the working pressures. It has been widely used on TIMS systems (by trapping the ions) and in drift tube (DT) systems, such as the inverted drift tube (IDT) , and the varying field drift tube (VFDT) . The VFDT is an atmospheric pressure instrument that employs a linearly decreasing electric field.…”

“…For a distribution of ions that are at an equilibrium point, ions that diffuse upstream, will be pushed forward due to the increase in the field and ions that diffuse downstream, will be pushed backward due to the decrease in the observed field. The VFDT can also correct the initial distribution, improving sensitivity for the same initial pulse and has been previously shown to have theoretical spatial resolving powers that are significantly higher than those of regular DTIMS under similar considerations . When the instrument was tested experimentally, its time-resolving power was only marginally higher than that of the DTIMS.…”

Field-Switching Repeller Flowing Atmospheric-Pressure Afterglow Drift Tube Ion Mobility Spectrometry

“…Drift tube ion mobility spectrometry (DTIMS) is an analytical separation technique based on the ions’ individual terminal velocity as they pass through a region with uniform electric field and drift gas performed mainly at atmospheric or subatmospheric pressure . DTIMS has been widely used for detection of chemical warfare agents, , environmental contaminants, narcotics, , aerosols, , proteomics investigations, − and gas-phase structural elucidations. , …”