A rapid method to empirically determine the presence of trace per- and polyfluoroalkyl substances (PFAS) in solid media, such as soils, sands, and sediments, without any sample preparation, through ambient ionization mass spectrometry (MS), is described. 3D-printed cone spray ionization (3D-PCSI) is an ambient ionization technique that employs a 3D-printed conductive plastic cone to perform both sampling and ionization. The 3D-PCSI sources are fabricated in the shape of a hollowed square pyramid to hold bulk matrices, and consist of rigid walls to aid in the uniformity and consistency of sampling and ionization. Solid samples are placed within the hollowed pyramid and a solvent is added to perform an in-situ extraction, followed by spray-based ionization when a voltage is applied. The low cost of 3D-printing, its reproducibility at scale, and lack of sample preparation, enables 3D-PCSI-MS to rapidly and efficiently screen for trace PFAS, in-situ, in bulk samples. Demonstrated here is the detection of trace PFAS that were doped into six different soil and sediment matrices, by 3D-PCSI-MS, to validate the universality of the method, irrespective of matrix composition. All PFAS were identified by their indicative MS3 spectra and ranged in detection limits from 100 ppt to 10 ppb depending on the compound and soil classification. Legacy aqueous film forming foams (AFFF) were analyzed in soil by 3D-PCSI-MS, as were soil samples collected around an AFFF testing facility. The sampling rate for 3D-PCSI-MS was less than 2 min per sample, demonstrating the applicability to high-throughput mapping of a contaminated area.
Keywords: 3D-printed cone spray ionization mass spectrometry; 3D-printing; Ambient ionization mass spectrometry; Aqueous film forming foams (AFFF); Per- and polyfluoroalkyl substances (PFAS); Soil analysis.
Published by Elsevier Ltd.