Rapid determination of melatonin by droplet spray ionization mass spectrometry

A new method based on droplet spray ionization mass spectrometry (DSI-MS) was developed for rapid qualitative and quantitative determination of melatonin products. Several different melatonin products were analysed with desvenlafaxine as internal standard. Samples only need to be dissolved and diluted without additional preparation procedures. The calibration curve was y = 0.45692 x − 0.00538 $\text{y}=0.45692\text{x}-0.00538$ with the square of correlation coefficient (R 2 ) of 0.9947 in the concentration range of 0.22–21.50 μM. The limit of detection (LOD) was 0.04 μM and limit of quantification (LOQ) was 0.17 μM, respectively. The recoveries were 88.4%–108.4% and the calculated RSDs were less than 12%. With this DSI-MS method, a single analysis can be completed within 1 min. This method inherent the advantages of rapid and accurate analysis, which can be used for qualitative and quantitative characterization of commercial melatonin products and quality control.