Steven M. E. Demers

Rationale: Because of their ubiquity in the environment and adverse health effects, per and polyfluoroalkyl substances (PFAS) are a growing area of concern to the public and regulatory agencies. The continued development of novel replacement PFAS necessitates the development of new methods to screen for these compounds. In this work, we demonstrate a method to detect multiple classes of PFAS including legacy PFAS, precursor compounds, and replacement compounds. Methods: Compounds were adsorbed to octadecylamine then analyzed by direct analysis in real time (DART) coupled with time‐of‐flight (TOF) mass spectrometry. Sixteen PFAS were analyzed from six distinct classes including perfluorinated carboxylic acids (PFCAs), perfluorinated sulfonic acids (PFSAs), per and polyfluoroalkyl ether carboxylic acids (PFECAs), polyfluoroalkyl ether sulfonic acids (PolyFESAs), fluorotelomer alcohol (FTOH), and perfluorooctane sulfonamidoacetic acid (FOSAA). These represent the classes considered in EPA method 537.1 and an additional important precursor class. Results: All six of the compound classes considered were successfully detected with this DART high resolution mass spectrometry (HRMS) method. Calculated lower limits of quantification ranged from 10 to 300 ng/L and were influenced by water matrix. The use of DART avoided instrumental background from solvents and tubing which is an established issue in liquid chromatography (LC) methods. DART–HRMS was also found to avoid false positives from compounds of similar molecular weights present in natural waters. Conclusions: The findings of this work fill an important gap in PFAS analysis by enabling screening for many known classes of PFAS. Furthermore, this method is anticipated to be able to analyze additional classes of PFAS as future replacement chemicals are produced, allowing for a more comprehensive analysis to be completed.

The self-activated cesium hafnium chloride (CHC) scintillator with cubic crystal structure is attracting tremendous attention due to its various advantages. Being self-activated, CHC offers uniform scintillator properties along the entire volume of the grown ingots irrespective of their sizes. The added advantage is excellent non-proportionality compared to other inorganic scintillators. There are wide variations of energy resolution values reported in the literature, the variations might be due to the different purity of the starting materials. In recent years, cesium zirconium chloride (CZC) scintillator and mixed scintillators with CHC are also gaining interest, as the atomic radius of Hf and Zr are equal. However, very limited information is available on the scintillator properties of CZC and CHZC in the literature. In this presentation, we will discuss the growth and characterization of CHC and CHZC scintillators grown by the vertical Bridgman technique. Our study shows the partial replacement of Hf by Zr improves the energy resolution compared to CHC grown by same growth parameters and purity of the starting material.

Rapid detection of nerve agents from complex matrices with minimal sample preparation is essential due to their high toxicity and bioavailability. In this work, quantum dots (QDs) were functionalized with oligonucleotide aptamers that specifically targeted a nerve agent metabolite, methylphosphonic acid (MePA). These QD-DNA bioconjugates were covalently linked to quencher molecules to form Förster resonance energy transfer (FRET) donor–acceptor pairs that quantitatively measure the presence of MePA. Using the FRET biosensor, the MePA limit of detection was 743 nM in artificial urine. A decrease in the QD lifetime was measured upon DNA binding and was recovered with MePA. The biosensor’s flexible design makes it a strong candidate for the rapid detection of chemical and biological agents for deployable, in-field detectors.