Acoustic ejection tandem mass spectrometry for high-throughput screening of phencyclidine-type substances in urine,...

The abuse of the Phencyclidine-type substances, especially ketamine is a serious problem worldwide, and retrospective analysis are important for both the analysis and the identification of forms of drug abuse. The current major analytical methods, while all excellent in terms of accuracy, are time- and reagent-consuming. This depletion is made even more unfortunate by the fact that a large number of samples are negative in retrospective analyses. It is clear that a set of methods that can be analyzed both accurately and quickly need to be developed and applied to the screening and analysis of large quantities of samples.

We described a urine test based on acoustic ejection mass spectrometry, which allows precise injection at very low volumes and near 1 ejection s^-1 and data acquisition. The confidence in identification was increased by the characterization of the abundance ratio of the two pairs of ions. Urine samples could be diluted with water and loaded into a 384-well plate for sampling without complicated sample preparation. The sample in the transparent 384-well plate was pre-scanned by the laser, and then 20 nL droplets were ejected into the ion source for targeted analysis of 2 ion transitions per droplet totaling 9 targeted analytes in the sequence of acquisition methods. It took 90 min to screen 250 samples in this approach, yielding 10 ng mL^-1 detection limits. Positive samples were further analyzed by UHPLC-MS/MS for confirmation and quantification of up to 36 analytes.

This was the first fast screening method for phencyclidine-type substances based on acoustic ejection mass spectrometry, which greatly reduces the analytical time, and can accomplish in 1.5 h what UHPLC-MS/MS needs 3 days to complete. And the samples can be analyzed without complicated sample preparation, and also can obtain good detectability. It was applied to a short-term retrospective analysis in Shanghai, and its accuracy was also extremely high.