Open AccessDevelopment of a novel microfluidic device to study metal geochemistry in situ using X‐ray fluorescence microprobe spectroscopy
Author(s) -
Chen Michael A.,
Kocar Benjamin D.
Publication year - 2021
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s1600577520016239
Subject(s) - microprobe , microscale chemistry , microfluidics , spectroscopy , fluorescence spectroscopy , x ray fluorescence , xanes , materials science , analytical chemistry (journal) , fluorescence spectrometry , in situ , fluorescence , chemistry , nanotechnology , mineralogy , optics , mathematics education , mathematics , physics , organic chemistry , quantum mechanics , chromatography
The study of in situ microscale biogeochemical processes represents a major challenge in the environmental sciences. The combination of microfluidic devices with X‐ray fluorescence microprobe spectroscopy may address this need, but typical materials used in these devices attenuate the X‐rays needed to analyze key elements of interest, such as Fe or As. In this work, a method is presented for fabricating an etched silicon microfluidic device that is sealed with a 30 µm thin glass window that is sufficiently transparent for X‐ray fluorescence microprobe spectroscopy. The capabilities of these devices for X‐ray microprobe spectroscopy are demonstrated using an Fe (hydr)oxide solid that is loaded with As and then infused with sulfide, on beamline 4‐BM at NSLS‐II, resulting in time‐variant Fe precipitation reactions and As sorption. Key results include in situ X‐ray fluorescence time‐series maps of Fe, As and a Br flow tracer, as well as spot XANES at both the Fe K edge and As K edge. Additionally, multiple energy mapping is used to examine the spatial speciation of As over time. The results of this work clearly demonstrate the capabilities of this novel microfluidic system that can be analyzed using X‐ray fluorescence microprobe spectroscopy and can be made to study a wide range of complex microscale geochemical systems.