Intercomparison study of fragmentation pathways and fragment ion structures for screening of illegal drugs and their novel analogues used to adulterate dietary supplements using liquid chromatography/quadrupole time-of-flight mass spectrometry.

ABSTRACT

RATIONALE As public interest in health and immunity has increased in recent years, so has the demand for dietary supplements. However, supplements adulterated with illegal drugs and their novel analogues are being sold even as the pharmacological efficacies of these drugs are being advertised. Since the use of these illegal compounds can have serious side effects, they pose a risk to public health. Hence, in this study, we propose a strategy for proactively testing drugs and novel analogues that may be added to dietary supplements illegally. METHODS: The optimal conditions for liquid chromatography/quadrupole time-of-flight mass spectrometry were explored to determine the fragmentation patterns for 60 compounds. The optimal conditions were established by comparing the areas and heights of the precursor ion peaks at a fragmentor voltage of 125 or 175 V. Furthermore, the optimized spectra were acquired using collision energies of 1 to 50 eV. The energy value was selected based on the condition that the mass error of the precursor ions is 10 ppm or lower. RESULTS: The fragmentation pathway of each product ion and its chemical structure were predicted and determined. In addition, the obtained structural information was used to screen 18 seized samples. Based on the precursor ions and the corresponding fragmentation patterns, the unknown compounds present in the samples were identified as desulfonylchlorosildenafil and propoxyphenylthiohydroxy homosildenafil. CONCLUSIONS: We obtained mass spectrometry-based information for various compounds by predicting the fragmentation pathways and chemical structures of their fragment ions. Subsequently, based on the obtained structural information, we tested several seized samples and were able to detect two novel analogues in four of the samples. Therefore, the proposed approach is suitable for quickly and accurately identifying the unknown compounds detected in real-world samples.