Array detector spectrometric systems

Samples are introduced into the capillary by either electrokinetic or hydrodynamic or hydrostatic means. Electrokinetic injection is preferentially employed with packed or monolithic capillaries whereas hydrostatic injection systems are limited to open capillary columns and are primarily used in homemade instruments. Optical detection directly through the capillary at the opposite end of sample injection is the most employed detection mode, using either a photodiode array or fluorescence or a laser-induced fluorescence (LIF) detector. Less common detection modes include conductivity [1], amperometric [2], chemiluminescence [3], and mass spectrometric [4] detection. 

Martens-Lobenhoffer et al. [119] used chiral HPLC-atmospheric pressure photoionization tandem mass-spectrometric method for the enantio-selective quantification of omeprazole and its main metabolites in human serum. The method features solid-phase separation, normal phase chiral HPLC separation, and atmospheric pressure photoionization tandem mass spectrometry. The internal standards serve stable isotope labeled omeprazole and 5-hydroxy omeprazole. The HPLC part consists of Agilent 1100 system comprising a binary pump, an autosampler, a thermo-stated column component, and a diode array UV-VIS detector. The enantioselective chromatographic separation took place on a ReproSil Chiral-CA 5 ym 25 cm x 2 mm column, protected by a security guard system, equipped with a 4 mm x 2-mm silica filter insert. The analytes were detected by a Thermo Scientific TSQ Discovery Max triple quadrupole mass spectrometer, equipped with an APPI ion source with a... 

Detection systems used for LC analysis of pesticides are UV spectrometric detection (especially diode array detection - DAD - allowing peak confirmation by means of spectra comparison), fluorescence detection (FLD), electrochemical detection (ED), evaporative light scattering detection (ELSD), and MSD. Their characteristic sensitivities can be considered to vary in the following order ELSDdetection systems mentioned above, only ELS and MS are universal detectors. 

If one compares the general situation of sample pretreatment/introduction in LC and GC, it should be clear that, with regard to this aspect, LG is certainly superior. This is especially true if aqueous samples are considered. The use of either disposable or reusable SPE cartridges (also called precolumns) packed with some 50 mg of an alkyl-bonded silica or highly hydrophobic copolymer sorbent, which are combined on-line with a (reversed-phase) LC system equipped with a diode-array UV-vis., a fluorescence or a mass spectrometric detector, enables... 

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