The analysis of marijuana and the determination of all ingredients is a subject of growing interest, but the determination of all compounds in natural samples such as marijuana is very challenging. On one hand, marijuana is used as an illegal psychoactive drug and the complete profile of the drug can help to identify where the plant has grown and to identify the producer but on the other hand, marijuana is used as an medicinal drug and there are strict legal regulations.
The complexicity of natural samples, such marijuana has led to the development of multidimensional chromatography techniques as comprehensive two dimensional gas chromatography (GCxGC), with a higher peak capacity compared to one-dimensional GC. Furthermore, the coupling of 1D- or 2D-GC with ion mobility-mass spectrometry (IM-MS) should drastically increase the peak capacity. But GCxGC-IM-qTOF-MS is hard to realize because no software is available, which can simplify the four-dimension data into a readable plot and the peak width after the second dimension (100-600 ms) is to narrow for IM-MS, because data acquisition of this instrument is too low. To overcome this and simplify data evaluation, a 2D-GC method with a longer modulation time (20 s) and a longer column (7 m) in the second dimension was developed.
Therefore, GC+GC-APCI-IM-MS was used to analyse an ethanol extract of marijuana. Figure 1 shows the contour plot of the GC+GC-APCI-IM qTOF-MS measurement. An Agilent 6560 Ion Mobility Quadrupole Time-of-Flight Mass Spectrometer was used in combination with a 6890N GC from Agilent and a four-jet modulator from Leco. About 100 spots have been detected. Furthermore, Figure 2 shows the separation of isobaric compounds, which could not be separated with 2D-chromatography and MS. To sum up, the GC+GC APCI-IM-qTOF-MS method works as a continuos multi-heartcutting approach with an outstanding separation power and allows the separation of compounds based on boiling point, polarity, size (shape)-to-charge and mass-to-charge ratio.