Superfund Research Program
Advanced Approaches to Quantifying Exposure to Heavy Metals
- Project Summary
Project Summary (2020-2025)
Historic and ongoing air, water, and soil pollution in North Birmingham results in area contamination with heavy metals and other toxic compounds and poses high health risks in the neighborhood. Analytical techniques for heavy metal (HM) detection are essential for understanding mechanisms of HM-induced lung injury and efficiency of mechanical and chemical remediation of pollution. The majority of current analytical techniques for HM detection, such as Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) and Atomic Absorption Spectrophotometry (AAS), are not portable, require large amounts of sample (ICP-MS), not always sufficiently sensitive, slow, and require advanced procedures for sample preparation.
The researchers’ hypothesis is that development of a novel femto-LIBS (laser-induced breakdown spectroscopy) / LEAFS (laser-excited atomic fluorescence spectroscopy) and middle infrared frequency comb "Optical Nose systems will enable ultrasensitive and rapid detection of Cd, Mn, As, and biomarkers associated with exposure to these metals.
LIBS is a rapid, real-time analytical technique based on the analysis of the spectral emission from laser-induced sparks. The method enables fast and sensitive chemical analysis of any kind of matter (solid, liquid, or gas) without sample preparation. Detection limits for LIBS using nanosecond laser pulses are typically in ppms for HMs. Excitation using laser pulses with femtosecond (fs) duration (f-LIBS) may provide significant improvement in detection limit. The researchers have demonstrated breakthrough in development of fs lasers based on chromium doped ZnS/Se crystals and have shown that these systems feature several essential advantages for fs laser spectroscopy applications. These lasers are a foundation for the f-LIBS platform.
The researchers’ objective is also to extend current visible-near IR frequency-comb techniques to molecules’ "fingerprint" mid-IR spectral range. The optical nose platform being developed is based on a dual-comb Fourier-transform spectroscopy with fs oscillators emitting in the mid-IR based on their recent breakthrough in fs lasers and their frequency down-conversion. The plan includes the development of 2-20 µm frequency combs on the basis of Cr:ZnS/Se fs laser and its intra-pulse difference frequency generation using ZnGeP2, GaSe and/or orientation patterned GaP nonlinear crystals. This planned instrument will provide a real-time total profile of the trace gas contents in complex gas mixtures and will be offered to other projects for sensing biomarkers associated with HM exposure.