New CDMS Instrument
The Jarrold Group is currently constructing a new CDMS instrument implementing devices designed previously by the Jarrold Group: a DC ion carpet, digitally scanned quadrupole appropriate for high mass ions, and a cylindrical cone trap capable of charge measurement with almost perfect precision. The new instrument will also be capable of surface/collision induced dissociation of large peptides and virus capsids.
DC Ion Carpet
A DC only ion carpet has been explored as an electrospray interface. The interface examined in our lab has a long drift region consisting of circular electrodes supplied with a DC gradient and RF voltages, with an ion carpet placed at the end of the drift region. The long drift region thermalizes and desolvates the ions, which are constrained radially by the RF. At the end of the drift region, the ion carpet transmits the ions through a small aperture. Simulations and experiments at a range of m/z values indicate that there is little m/z bias, and when the gradient is optimized, the DC ion carpet provides a high transmission efficiency.
Digitally Scanned Quadrupole
A new quadrupole using a primary frequency scan with a superimposed, narrow-range amplitude scan. Because the frequency is the primary quantity scanned, the upper m/z limit can be made arbitrarily large. Trapezoidal waves are used to generate the oscillating electric fields in the QMF. With a trapezoidal waveform the contribution from harmonics can be minimized by adjusting the length of the transition times. The m/z resolving power is much better than has been obtained with a frequency scan in the past