Multiple-source precursor

Terpenoids are classified according to the number of five-carbon multiples they contain. Monoterpenoids contain 10 carbons and are derived from two isopentenyl diphosphates, sesquiterpenoids contain 15 carbons and are derived from three isopentenyl diphosphates, diterpenoids contain 20 carbons and are derived from four isopentenyl diphosphates, and so on, up to triterpenoids (C30) and tetraterpenoids (C40). Monoterpenoids and sesquiterpenoids are found primarily in plants, bacteria, and fungi, but the higher terpenoids occur in both plants and animals. The triterpenoid lanosterol, for example, is the precursor from which steroid hormones are made, and the tetraterpenoid /3-carotene is a dietary source of vitamin A (Figure 27.6). 

By CH4-chemical ionization two predominant ions from DDS were formed in the ion source m/z 163 (M + 1) and m/z 165 (M + 3), which were accelerated and separated in the first quadrupole. Decomposition by collision activation with argon then occurred in the second quadrupole and the resulting daughter ions were separated in the third quadrupole to give rise to collision-induced spectra (equations 41-43). When carrying out the analysis with a solid inlet MS-MS system (TSQ) it was observed that, when operating TSQ in the multiple ion detection mode and selecting the ions m/z 63, 83, 85,99 and 101, only in the third quadrupole was there no interference from other m/z 163 and 165 precursor ions . ... 

The desired long spacer necessary to allow multiple branch construction, was obtained with commercial tetra(ethylene glycol) which was readily modified into aminoacetal 21 in five steps (Scheme 8). Using 21 as an amine source, poly(amidoamine) (PAMAM) dendrons were prepared according to published protocol using reiterative cycles of methyl acrylate and ethylenediamine reactions. The terminal amines of each generation (G = 1, G = 2 and G = 3, 22a-c) were obtained quantitatively from each of the half generation methyl ester precursors. 

Inhomogeneity is quite naturally predicted to occur in this class of complexes. This is not only due to the different possible breakdown pathways in soils, sediments, etc., but is also due to the multiplicities of naturally occurring precursors in living organisms. For example, a number of known chlorophyll structures are shown in (23). The structural complexity is even more elaborate for the haems. Mixtures in geological media thus are to be expected. However, it should be pointed out that the amount of porphyrins from plant sources is overwhelming compared to that... 

For the detection, a tandem mass spectrometer Quattro Micro API ESCI (Waters Corp., Milford, MA) with a triple quadrupole was employed. The instrument was operated in electrospray in the positive ionization mode (ESI+) with the following optimized parameters capillary voltage, 0.5 kV source block temperature, 130 °C nebulization and desolvation gas (nitrogen) heated at 400 °C and delivered at 800 L/h, and as cone gas at 50 L/h collision cell pressure, 3 x 1(F6 bar (argon). Data was recorded in the multiple reaction monitoring (MRM) mode by selection of the two most intense precursor-to-product ion transitions for each analyte, except for the ISs, for which only one transition was monitored. The most intense transition for each analyte was used for quantitative purposes. Table 2 shows MRM transitions, cone voltages and collision energies used for the analysis of the antidepressants included in the LC-MS/MS method. 

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