Quadrupole offset voltage - TSQ Quantis Plus MS - TSQ Fortis Plus MS - TSQ Series - TSQ Altis MS - TSQ Quantis MS - TSQ Altis Plus MS - TSQ Fortis MS - Quadrupole offset voltage - TSQ Quantis Plus MS - TSQ Fortis Plus MS - TSQ Series - TSQ Altis MS - TSQ Altis MS - TSQ Quantis MS - TSQ Quantis MS - TSQ Altis Plus MS - TSQ Fortis MS

The quadrupole offset voltage is a DC potential applied to the quadrupole rods in addition to the resolving DC voltage. The offset voltage applied to the two rod pairs of the assemblies is equal in amplitude and opposite in sign. The quadrupole offset voltage accelerates or decelerates ions and, therefore, sets the kinetic energy of the ions as they enter the quadrupole rod assembly.

In MS modes of operation, the instrument uses a fixed or slowly varying voltage offset between Q1 and Q3. However, in MS/MS experiments, the quadrupole offset voltage applied to Q2 and Q3 usually varies as acquisition proceeds. The MS automatically computes the necessary Q3 quadrupole offset voltage and then varies the voltage, as appropriate, as each scan proceeds.

The offset voltage applied to Q2 (which contains the collision cell) is responsible for the collision energy. The collision energy is the difference in potential between the region where ions start being governed mostly by the electric forces (in the vicinity of Q0, which is also known as MP0) and Q2 (where they collide with collision gas). As the offset voltage on Q2 increases, so does the kinetic energy of the precursor ions. As a result, the energy of ion/Ar (or ion/N) collisions also increases. You can set the collision energy from 0 to ±65 V in the first two generations of TSQ Series II mass spectrometers and from 0 to ±120 V in the current generation of TSQ Series II mass spectrometers.

During tuning, the MS determines the optimum mass-dependent quadrupole offset voltage for Q1 and for Q3.