Developing a detection strategy for ten paralytic shellfish poisonings in urine, combining high-throughput DESI-MS screening and accurate UPLC-QqQ/MS quantification.

Paralytic shellfish poisoning (PSP) is the most widespread and harmful form of shellfish poisoning with high mortality rate. In this study, a combined desorption electrospray ionization mass spectrometry (DESI-MS) and ultra-performance liquid chromatography triple quadrupole mass spectrometry (UPLC-QqQ/MS) method was established for the detection of PSPs in urine. The method was optimized using a spray solution of methanol and water (1:1, v/v) containing 0.1 % FA, at a flow rate of 2.5 µL·min-1 and an applied voltage of 3 kV. The limit of detection (LOD) for PSPs detection by DESI-MS was in the range of 87-265 μg·L-1, which basically meets the requirements for the rapid screening of PSPs. The LOD for UPLC-QqQ/MS was in the range of 2.2-14.9 μg·L-1, with a limit of quantification (LOQ) of 7.3-49.7 μg·L-1, thus fulfilling the quantitative demand for PSPs in urine. Finally, after spiking the urine samples of six volunteers with PSPs to a concentration of 100 μg·L-1, DESI-MS successfully and efficiently detected the positive samples. Subsequently, UPLC-QqQ/MS was employed for precise quantification, yielding results in the range of 84.6-95.1 μg·L-1. The experimental findings demonstrated that the combination of DESI-MS and UPLC-QqQ/MS enables high-throughput, rapid screening of samples and accurate quantification of positive samples, providing assurance for food safety and human health.