Detection systems quadrupole type

Chromatographic systems were finally coupled with relatively inexpensive, yet powerful, detection systems with the advent of the quadrupole mass selective detector (MSD). The operational complexity of this type of instrumentation has significantly declined over the last 15 years, thus allowing routine laboratory use. These instruments... 

GC detection systems for trichothecenes primarily featured classical detectors such as ECD, especially for fiuorinated derivatives however, mass spectrometers are nowadays routinely used for this purpose. The selectivity of a detector is an important issue as trichothecenes are present in relatively complicated matrices and create high background during the analysis. Three types of mass spectrometers have been used for trichothecene analysis by GC/MS, and quadrupole instruments are used most frequently. 

With NQR the electric induction gradient is a molecular or solid-state property and is considerably larger than any practical externally applied field gradient. This implies that a variable-frequency detection system must be used. The NQR frequencies for the various nuclei vary from 100 kHz up to 1 GHz, making detection by a single spectrometer very difficult. Their values depend on quadrupole moments of the nucleus, the valence electrons state and the type of chemical bonds in which the studied atom participate. 

The coupling of a mass spectrometer to CE and CEC provides a powerful system for the analysis of pharmaceuticals and complex biological mixtures. This can replace or complement other conventional detection methods such as UV, electrochemical, or LIE that provide less structural information. The use of mass spectrometer as a detector enhances the usefulness of the CE and CEC and allows an efficient separation and identification of complex mixtures, obtaining structure and/or molecular mass information. The choice of mass analyzers used in CE/CEC-MS depends on factors such as sensitivity, mass resolution, requirement for structural elucidation, and the type of application (Table 5). The analyzers that have been used in CEC analysis include time-of-flight (TOE), quadrupole (Q), ion-trap (IT), fourier... 

Commercially available GC-MS systems present major differences in their detection and recording system. Many quadrupole instruments use SIM for the determination of analytes at trace levels. With this type of instrumentation, more than 1-10 ng of the analyte is required to record a full-scan mass spectrum. In contrast, instruments based on ion-trap technology can record a full-scan mass spectrum on an analyte at pg level. With SIM, a limited number of ions are monitored during a selected time interval of the chromatogram. The presence of the analyte is determined by the presence of these diagnostic ions at the correct retention time and in the correct abundance ratio (33). 

The choice of GC conditions employed was left to the discretion of the seven participating laboratories. Instrument types used in this study included three quadrupole systems and four magnetic sector instruments. One of the laboratories performed the analyses using both electron capture and mass spectral detection. Two laboratories performed the analysis at a high resolving power (RP > 10,000) while others used the mass spectrometer operating at nominal resolution. All laboratories performed the analysis under ECNI conditions... 

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