Detectors corona discharge

An ion mobility spectrometer consists of a sample-introduction device a drift tube where ionisation and separation of ions takes place and a detector. Ionisation sources of choice include radioactive sources (e.g. a 63Ni foil), photoionisation methods, corona-spray ionisation, flame ionisation and corona discharge. The most common detection method used to measure the... 

Various mass spectrometer configurations have been used for the detection of explosives, such as ion traps, quadrupoles and time-of flight mass analyzers and combinations as MS/MS systems. The ionization method is usually APCI with corona discharge [24, 25]. An example is given in Figure 20, which shows the schematic diagram of an explosive mass spectrometer detector [25]. It is based on an ion trap mass analyzer, an APCI source with corona discharge and a counter-flow introduction (CFI) system. The direction of the sample gas flow introduced into the ion source is opposite to that of the ion flow produced by the ion source. 

TABLE 53.7. Detection performance of corona discharge-type IMS detector LCD-3.2E... 

Detector MS, SCIEX API III, atmospheric pressure ionization, nebulizer probe 450°, 2.5 (juA Corona discharge needle, quadrupole mass filter, 0.002 inch pinhole aperture, SIM m/z 749 and 752... 

Detector MS, PE Sciex API III, heated nebulized interface, corona discharge needle +4 xA, nebulizer probe 500°, nebulizing gas was air at 2 L/min and 80 psi, curtain gas flow was nitrogen at 0.9 L/min, sampling orifice +45 V, dwell time 400 ms, interface heater 60°, electron multipher-3.7 kV, collision gas was argon 355 x 10 atoms/cm, first quad-rupole filter admits m/z 276 (cyclobenzaprine) and 295 (trimipramine, collisional fragmentation at second filter, monitor m/z 215 (cyclobenzaprine) and 208 (trimipramine) at third quadrupole filter... 

Detector MS, PE-SCIEX API III triple quadrupole, heated nebulizer, corona discharge (+5 pA), positive ion APCI, nebulizer probe 500°, collision gas argon at 350 X 10 mole-cules/cm, nebulizing gas nitrogen at 80 psi and 2 L/min, curtain gas nitrogen at 0.9 L/min, orifice -1-50 V, electron multiplier -3.8 kV, dwell time 400 ms, interface heater 60°, m/z 317... 

Detector MS, Sciex Model API III triple quadrupole, nebulizer probe 500°, nebulizing gas 80 psi, auxiliary flow 2 L/min, corona discharge needle -1-3 p,A, 0.1143 mm orifice, orifice 40 V, collision gas argon... 

Schematic of a typical ion mobility spectrometer is shown in Fig. 1. An ion mobility spectrometer consists of an ionization source, an ion mobility drift tube, a detector, and supporting electronics. The samples are usually ionized by radioactive Nickel-63, electrospray ionization source, corona discharge, or photoionization source. The ions travel through the drift tube while colliding with the medium molecules, usually air or nitrogen, at atmospheric pressure. The resulting ion velocity is proportional to the applied electric field and mobility of the ion.

Other detectors to be mentioned are the fluorescence detectors, the light scattering detectors, the electrochemical detectors, the refractive index (RI) detectors, the conductivity detector, and the corona discharge detector, as well as detectors for measurement of radioactivity, optical rotation, and NMR. 

The ESI source apparently suffers from the limitation that it cannot accept more than 40—50 xL/min of the LC mobile phase. These flow rates are compatible with 1 mm ID LC columns. Or, the effluent from a conventional 4.6 mm ID LC column can be partially diverted by a split device to the ESI source. As the ESI-MS arrangement is a concentration-sensitive detector, diverting only a fraction of the LC mobile phase does not affect sensitivity. Another way of overcoming the problem of coupling LC with 4.6 mm ID conventional columns is that of inducing analyte ionization by gas-phase ion-molecule reactions under APCI conditions. Reactant ion formation is achieved by the introduction of electrons from a corona discharge located in the chamber at atmospheric pressure. In this way, reversed-phase LC effluents can be handled as high as 2 mL/min. 

Detector MS, Finnigan LCQ, APCI, corona discharge 4.5 kV, vaporization 430°, capillary 150° 32 V, positive mode, m/z 296.2... 

Detector MS, PE Sciex API-Ill, triple quadrupole, orifice 45 V, nebulizer probe 470°, nebulizer gas at 550 kPa, auxiliary fiow 1.5 L/min, corona discharge needle 3 (xA, m/z 212-153... 

TABLE 60.6 Detection Performance of Corona Discharge-Type Short Drift Tube IMS Detector LCD-3.2E... 

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