Pesticides selected-reaction monitoring

Table 5.2 Selected-reaction monitoring (SRM) transitions nsed for MS-MS detection of the pesticides studied in the systematic investigations on APCI-MS signal response dependence on eluent flow rate. Reprinted from J. Chro-matogr.. A, 937, Asperger, A., Efer, J., Koal, T. and Enge-wald, W., On the signal response of various pesticides in electrospray and atmospheric pressure chemical ionization depending on the flow rate of eluent applied in liquid chromatography-mass spectrometry , 65-72, Copyright (2001), with permission from Elsevier Science...

Whereas most multiresidue methods employ SPE for sample enrichment, Grulick and Alder [80] utilized direct sample injection for the determination of 300 pesticides in water samples. A conventional reversed-phase LC separation was developed with gradient elution using a Cl 8 column with a run time of approximately 23 min. The LC was coupled to a triple quadrupole mass spectrometer with electrospray ionization in the positive ion mode. Two selected reaction monitoring transitions were collected for each analyte by means of repeated analyses (i.e., two sample injections). Because interfering signals were noted for many of these transitions, both the LC separation and confirmatory transitions were essential for correct analyte identification. 

Keywords pesticides food multi-residue method high throughput QuEChERS SRM (selected reaction monitoring) H-SRM (enhanced resolution selected reaction monitoring) MS/MS confirmation QED data-dependent acquisition... 

For trace analysis, in which full-scan data cannot be obtained and selected ion monitoring (SIM) or multiple reaction monitoring (MRM) is required, no criteria have been established by the OPCW. Rodriguez and Orescan (23) proposed the following criteria for confirmation of trace levels of pesticides by LC/API/MS under MS conditions that promoted in-source CID ... 

Because process mixtures are complex, specialized detectors may substitute for separation efficiency. One specialized detector is the array amperometric detector, which allows selective detection of electrochemically active compounds.23 Electrochemical array detectors are discussed in greater detail in Chapter 5. Many pharmaceutical compounds are chiral, so a detector capable of determining optical purity would be extremely useful in monitoring synthetic reactions. A double-beam circular dichroism detector using a laser as the source was used for the selective detection of chiral cobalt compounds.24 The double-beam, single-source construction reduces the limitations of flicker noise. Chemiluminescence of an ozonized mixture was used as the principle for a sulfur-selective detector used to analyze pesticides, proteins, and blood thiols from rat plasma.25 Chemiluminescence using bis (2,4, 6-trichlorophenyl) oxalate was used for the selective detection of catalytically reduced nitrated polycyclic aromatic hydrocarbons from diesel exhaust.26... 

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