Research in our group revolves around analytical chemistry with a special focus on direct surface analysis, ultra trace elemental and nanoparticle analysis, speciation, plasma sciences, and instrumentation.
We use techniques such as Ambient Desorption/Ionization Mass Spectrometry (ADI-MS), Inductively Coupled Plasma – Mass Spectrometry (ICP-MS), Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES), Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), and Pulsed Radio-frequency Glow Discharge – Optical Emission Spectrometry (rfGD-OES).
Research Highlight I:
Direct Surface Analysis
Direct surface analysis of solid and liquid samples can be performed by ambient desorption/ionization mass spectrometry (ADI-MS) with little to no sample pretreatment and low limits of detection. Since the inception of the technology a few years ago, a variety of plasma-based desorption/ionization sources have been published, but little has been reported on the fundamental processes and reaction mechanisms responsible for analyte ionization. In a collaboration with George C.-Y. Chan, Jacob T. Shelley, Gary M. Hieftje (Indiana University), Joshua S. Wiley, Ayanna Jackson, and R. Graham Cooks (Purdue University) fundamental studies on the low-temperature plasma probe (LTP) have been performed. In addition, we are currently using ambient ionization sources with a high-resolution mass spectrometer (Orbitrap) for direct analysis of various types of samples.
A. Albert, J.T. Shelley, C. Engelhard*:
Plasma-based Ambient Desorption/Ionization Mass Spectrometry: State-of-the-art in Qualitative and Quantitative Analysis,
Anal. Bioanal. Chem., 2014, 406(25), 6111-6127 (DOI:10.1007/s00216-014-7989-z).
Featured by Anal. Bioanal. Chem. on the Cover of issue 25.
A. Albert, C. Engelhard*:
Chemometric Optimization of a Low-Temperature Plasma Source Design for Ambient Desorption/Ionization Mass Spectrometry,
Spectrochim. Acta, Part B, 2015, 105, 109-115 (DOI: 10.1016/j.sab.2014.08.034).
A. Albert, A. Kramer, S. Scheeren, C. Engelhard*:
Rapid and Quantitative Analysis of Pesticides in Fruits by QuEChERS Pretreatment and Low-Temperature Plasma Desorption/Ionization Orbitrap Mass Spectrometry,
Anal. Methods, 2014, 6(15), 5463-5471 (DOI:10.1039/C4AY00103F).
Featured by Anal. Methods on the Front Cover of Issue 15.
B. Vortmann, S. Nowak, C. Engelhard*:
Rapid characterization of lithium-ion battery electrolytes and thermal aging products by low-temperature plasma ambient ionization high-resolution mass spectrometry,
Anal. Chem., 2013, 85 (6), 3433−3438 (DOI: 10.1021/ac4001404).
A. Albert, C. Engelhard*:
Characteristics of low-temperature plasma ionization for ambient mass spectrometry compared to electrospray ionization and atmospheric pressure chemical ionization,
Anal. Chem., 2012, 84 (24), 10657–10664 (DOI: 10.1021/ac302287x).
G. C.-Y. Chan, J. T. Shelley, J. S. Wiley, C. Engelhard, A. U. Jackson, R. G. Cooks, G. M. Hieftje:
Elucidation of Reaction Mechanisms Responsible for Afterglow and Reagent-Ion Formation in the Low-Temperature Plasma Probe Ambient Ionization Source,
Anal. Chem., 2011, 83 (10), 3675–3686. (DOI: 10.1021/ac103224x).
G. C.-Y. Chan, J. T. Shelley, A. U. Jackson, J. S. Wiley, C. Engelhard, R. G. Cooks, G. M. Hieftje:
Spectroscopic Plasma Diagnostics on a Low Temperature Plasma Probe for Ambient Mass Spectrometry,
J. Anal. At. Spectrom., 2011, 26(7), 1434-1444. (DOI: 10.1039/C0JA00230E).
Research Highlight II:
Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool for ultra trace analysis. In our group, ICP-MS is used for the detection, identification, and characterization of single nanoparticles in complex matrices. Conventional and single-particle detection mode as well as various sample introduction strategies are optimized for highly sensitive nanoparticle detection.
I. Strenge, C. Engelhard, J. Anal. At. Spectrom., 2016, 31(1), 135-144 (DOI: 10.1039/c5ja00177c).
B. Franze, C. Engelhard, Anal. Chem., 2014, 86(12), 5713-5720 (DOI:10.1021/ac403998e).
B. Franze, I. Strenge, C. Engelhard, J. Anal. At. Spectrom., 2012, 27(7), 1074-1083 (DOI: 10.1039/C2JA00003B).
C. Engelhard, Anal. Bioanal. Chem., 2011, 399(1), 213-219.
C. Engelhard et al., J. Anal. At. Spectrom., 2008, 23 (3), 407-411.
Research Highlight III:
Elemental Imaging and Speciation Analysis with a Large-format Pulsed Glow Discharge
In a collaborative effort with Prof. Gary M. Hieftje, Dr. Steven J. Ray (Indiana University), Dr. Volker Hoffmannn, Dr. Maxim Voronov (IFW Dresden), and Dr. Wolfgang Buscher, Unversity of Münster, we are currently involved in the development of new instrumentation for elemental imaging and speciation analysis. In this project it was demonstrated that a pulsed rf-glow discharge coupled to a monochromatic imaging spectrometer can provide spatially resolved elemental information – i.e. detect and quantitate proteins on gels after gel electrophoretic separations. Currently, a large-format glow discharge prototype instrument is being optimized for the analysis of large-format samples.
This project is funded by the German Research Foundation (DFG) and the National Science Foundation (NSF).
M. Voronov et al., J. Anal. At. Spectrom., 2012, 27, 419-425 (DOI: 10.1039/c2ja10325g).
M. Voronov et al., J. Anal. At. Spectrom., 2011, 26(4), 811-815.
C. Engelhard et al., J. Anal. At. Spectrom., 2010, 25(12), 1874-1881.