No abstract

An automated liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method is presented for the screening and confirmation of 16 beta-blocking drugs in clinical and autopsy urine samples. The described method involved C(18) solid phase extraction, LC separation and MS analysis on a triple-stage quadrupole mass analyser. Samples were initially pre-screened for the presence of any beta-blocking drugs using LC/MS with selected ion monitoring. Any compounds tentatively identified as beta-blocking drugs on the basis of their LC retention time and protonated molecular ion were then automatedly subjected to a second analysis in which the relevant MS/MS product ion mass spectra were acquired. These product ion mass spectra were then automatically searched against a 400-substance mass spectral library containing previously acquired beta-blocking drugs. The results demonstrated that library search of beta-blocking drugs in urine with MS/MS product ion mass spectra was more reliable and produced fewer false negatives than library searching with mass spectra derived from single-stage quadrupole MS. The limits of identification in the MS/MS product ion scan ranged from 0.02 mg l(-1) for carvedilol to 1.2 mg l(-1) for pindolol, the majority of the values being below 0.2 mg l(-1).

No abstract

Isoprenoids, the general class of natural products biosynthesized from isoprene units, are abundant in nature. Many isoprenoids are also found in sediments, sedimentary rocks and crude oils where they have proved useful as 'chemical fossils' of biological activity and as indicators of geothermal stress. However, acyclic isoprenoids with 25 carbon atoms-so-called sesterterpenoids-have been reported only rarely in the biosphere and the geosphere. Indeed, the only acyclic sesterterpenoids of confirmed structure reported in sediments are of pentamethyleicosane structural isomers (Fig. 1, carbon skeleton I). For example, 2,6,10,14,18-pentamethyleicosane has been proposed as a marker for halophilic bacteria and the 2,6,10,15,19-isomer (I) as an indicator of methanogens. We have now identified a group of novel sesterterpenoids that are major components of the hydrocarbons of recent freshwater, marine and hypersaline sediments from many different parts of the globe. Because they have unusual structures, these sesterterpenes show promise as a new class of biological marker compounds.

No abstract