Comparison of liquid chromatography-high-resolution tandem mass spectrometry (MS²) and multi-stage mass spectrometry (MS³) for screening toxic natural products

Background: Liquid chromatography-high-resolution mass spectrometry (LC-HR-MS) has emerged as a powerful analytical technology for compound screening in clinical toxicology. To evaluate the potential of LC-HR-MS³ in detecting toxic natural products, a spectral library of 85 natural products (79 alkaloids) that contains both MS² and MS³ mass spectra was constructed and used to identify the natural products. Samples were analyzed using an LC-HR-MS³ method and the generated data were matched to the spectral library to identify the natural products.

Methods: To test the performance of the LC-HR-MS³ method in different sample matrices, the 85 natural product standards were divided into three groups to separate structural isomers and avoid ion suppression effects caused by co-elution of multiple analytes. The grouped analytes were spiked into drug-free serum and drug-free urine to produce contrived clinical samples.

Results: The compound identification results of the 85 natural products in urine and serum samples were obtained. The match scores using both MS² and MS³ mass spectra and those using only MS² mass spectra were compared at 10 different analyte concentrations. The two types of data analysis provided identical identification results for the majority of the analytes (96% in serum, 92% in urine), whereas, for the remaining analytes, the MS²-MS³ tree data analysis had better performance in identifying them at lower concentrations.

Conclusion: This study shows that in comparison to LC-HR-MS (MS²), LC-HR-MS³ can increase the performance in identification of a small group of the toxic natural products tested in serum and urine specimens.