Post-ICP Chemical Ionization MS for Total Extractable Organic Fluorine Quantitation

Total extractable organic fluorine (EOF) quantitation complements targeted analyses to ensure complete accounting of all fluorochemicals in a sample. Notably, the prevalence of perfluoroalkyl substances has increased the need for total EOF quantitation due to the myriad forms of these chemicals and the limited availability of standards for targeted analysis. Here, we evaluate postplasma chemical ionization mass spectrometry (MS), an approach developed to address the limitations of inductively coupled plasma (ICP)-MS in F analysis, for total EOF quantitation. Organofluorine-containing samples are introduced into an ICP, leading to the post-ICP formation of HF, which is then ionized to ScFNO₃(H₂O) ⁺ and detected by quadrupole MS. We report optimal F detection across a wide range of ICP operating parameters, highlighting robust ion generation processes. We then compare sample introduction methods and show that a single-pass spray chamber mitigates volatility-related biases, yielding compound-independent F response factors and an instrumental detection limit of 2.2 ng of F mL^-1 by using flow injections. This detection limit is 10-fold better than that offered by ICP-MS and comparable to that of combustion ion chromatography. Subsequently, we conduct total EOF quantitation of food contact paper products via methanolic extraction of 3 cm × 3 cm samples followed by 8-fold preconcentration with solid phase extraction and flow injections, achieving a detection limit of 1.2 ng F cm^-2. We show that organic fluorine is detected on all 9 locally collected food contact paper products with total EOF contents of 22-363 ng F cm^-2. These studies expand elemental MS capabilities in F analysis and highlight post-ICP chemical ionization MS as a facile total EOF quantitation technique.