Rapid Detection\nof Trace Organic Amines in Seawater:\nAn Innovative Approach Using Photoelectron-Induced Chemical Ionization\nTOFMS with Online Derivatization and Dynamic Purging-Release Techniques

Organic amines (OAs) have gained substantial interest\nin atmospheric\nchemistry due to their distinctive acid–base neutralization\ncharacteristics for secondary organic aerosols and new particle formation.\nTo address the need for sensitive and online analysis of OAs, including\ndimethylamine (DMA), diethylamine (DEA), trimethylamine (TMA), and\ntriethylamine (TEA), in seawater, a home-built photoelectron-induced\nchemical ionization TOFMS, coupled with online derivatization and\ndynamic purge-release apparatus, has been developed. Sodium hypochlorite\nis used to derivatize high-solubility DMA and DEA, substituting hydrogen\natoms with chlorine atoms to obtain more volatile derivatives, [DMA-H\n+ Cl] and [DEA-H + Cl]. Sodium carbonate is used to reduce the solubility\nof the OAs in solution to enhance detection sensitivity. Microbubbles\ngenerated from 250 to 300 mL/min of zero air at the gas–liquid\ninterface efficiently transfer dissolved OAs into the gas phase. Water\nvapor in the purged gas is ionized by photoelectrons to form (H<sub>2</sub>O)<sub><i>n</i></sub>·H<sup>+</sup>, which\nionizes OAs and their derivatives to produce characteristic ions [OAs\n+ H]<sup>+</sup> or [OAs-H + Cl]·H<sup>+</sup> characteristic\nion. After optimizing the experimental conditions, the limits of quantification\n(S/N = 10) of the four OAs including DMA, DEA, TMA, and TEA can be\nas low as 1.1 0.68, 0.85, and 0.49 nmol/L, respectively within a 5\nmin analysis time, using only 5 mL of seawater sample. This method\nenhances sensitivity by over 5-fold and reduces analysis time to 21.7%,\nrespectively, compared with conventional methods. Subsequently, this\nmethod was successfully applied to quantify 15 seawater samples from\n5 typical marine environments, which demonstrates its practicability\nand reliability for analysis of trace amines in seawater.