38 February / March 2017 forensic analytes in urine at spiking level 1.
This analytical technique shows that even with a rapid LC gradient of less than 3 minutes, a full comprehensive profile of the sample can be built. Figure 6 shows the true positive rate at the varying concentration levels. Even at the low levels found in sample 1 there is still a 96% positive detection.
Figure 4: Details of the settings for the acquisition on the X500R QTOF system
Unknown 1 and 2 were quality control urine samples spiked with all the analytes at different levels. Sample 3 through 20 were true unknown samples. There was a total of 82 true positive identifications from Sample 3 to Sample 20. For quantitation, the TOF-MS data from SWATH® acquisition can be used. It is worth mentioning that the MS/MS data from this acquisition can also be used for quantitation and compound identification through ion ratios, but we did not test that in this study but has been demonstrated in a previous study [6].
This full scan acquisition technique yielded excellent positive detection due to its complete coverage of MS/MS information. One of the key features of this scan type is the ability to create a digital archive of your sample, as this is an MSAll
experiment Figure 5: Examples of extracted chromatograms at level 1 spike in urine.
time, and it significantly improves the MS/MS data quality by allowing sequentially programed Q1 isolations therefore more selective MS/MS data collection compared to other MS/MSAll
techniques. Figure 3 shows the principal behind this acquisition
experiment and Figure 4 details the settings for this acquisition on the X500R QTOF system.
Analysis of the data at spiking level 1 shows clear resolution and separation with confident identification. Figure 5 shows the extracted ion chromatograms of selected
of everything is scanned. The sample only needs to be injected once and the analysts will have a full insight as to what compounds are present in their sample, the analyst can return to this sample and re-interrogate the data at any time. There is no need to re-run a sample, which may have been subjected to degradation and thus forensic analytes may no longer be traceable. This means that if a brand new NPS enters the drug scene the acquisition will view the unique spectra attributed to the new forensic compound and begin to facilitate identifying the type of designer drug that has entered supply.
Conclusion
In this example, it has been demonstrated that tackling the chromatographic analysis of novel psychoactive substances with High Resolution Mass Spectrometry can be highly effective using an ultra-fast chromatographic separation technique coupled with a QTOF mass spectrometer. Non-targeted SWATH acquisition affords retrospective data analysis which is critically important for the rapidly emerging new designer drugs.
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