A drug of abuse sample is analyzed by GC-MS by using the sample introduction met

Question

A drug of abuse sample is analyzed by GC-MS by using the sample introduction method based on a Curie Point pyrolyzer. The two overlaid chromatograms of samples analyzed by pyrolysis at 358 ºC and 590 ºC are shown in Figure 1a along with the mass spectra collected at various retention times. Figure la Pyrolysis at 590 C Pyolysis at 358 C Figure 1C Figure id Figure le Figure 1. (a) GC-MS analysis ofa drugsample by pyrolysis at 358 "Cand 590 C(b) Mass spectrum at Scan 1298 or 17.23 min for pyrolysis temperature of at358 "C (c) Identified molecular structure for Scan 1298 or 17.23 min: (d &e;) Mass spectra at39.92 min and 40.75 min for pyrolysis temperature of at 590 "Care identified as methanones, the main psychoactive constituents in the drugofabuse.

Explanation / Answer

Figure 1c: Molecular mass for the given structure (C12H12O2) is 188.08 g/mol.

Figure 1d:Molecular mass for the given structure (C23H21NO) is 327.16 g/mol.

Figure 1e:Molecular mass for the given structure (C24H23NO) is 341.18 g/mol.

Yes, molecular ions are readily observed in the mass spectra obtained with electron impact (EI) ionization. Sometimes, the source structure may undergo molecular fragmentation if more energy is provided, i.e., at high temperature.

Electrospray ionization (ESI) mass spectrometry can be used to produce more prominent molecular ions by reducing the extent of molecular fragmentation.

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