Quadruple MS also known as Q-MS are quite popularly used in drug testing as mass analyzers. For many years, these instruments while being used in SIM method are taken as a ‘Gold Standard’ to confirm and quantify drugs and their metabolites in forensic laboratories. The Q-MS is basically a mass filter which is also referred as MSD – Mass Selective Detectors.
Q-MS contains 4 circular or hyperbolic rods which have the same spacing and measurements. It is elaborated in Figure 3.1. The rods which are diagonal, have same dc – direct current charge which is run through them, where as the adjacent rods contain contrary charge. A regular direct voltage is passed through with an RF – radio frequency which is contrary to the opposite quadruples. The ions are forced into the area of quadruple by focusing lenses. At a particular dc/RF, the ions can undergo fluctuations which follow in a corkscrew pattern to the detector. Other ions which crash into the rods or walls of MS compartment do not reach the detector. That is the reason why mass filters are known as Q-MS. The computer aided and electronic analysis, sweeps the dc/RF signals which detects the mass range of the dynamic range i.e. m/z. The dc/RF passes quickly and is measured in milliseconds which allow the MS to scrutinize the mass range a lot of times before the molecules vacuum out through the system. The scanned data is then compiled by a computer which yields the mass spectrum depicting the m/z and its intensity.