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Analytical Ion Spectroscopy

Combining the individual analytical strengths of mass spectrometry and infrared spectroscopy, infrared ion spectroscopy is increasingly recognized as a powerful tool for small-molecule identification in a wide range of analytical applications.

Mass spectrometry is itself a leading analytical technique for small-molecule identification on the merit of its outstanding sensitivity, selectivity and versatility. The foremost shortcoming of the technique, however, is its limited ability to directly probe molecular structure, especially when contrasted against spectroscopic techniques.

In infrared ion spectroscopy (IRIS), infrared vibrational spectra are recorded for mass-isolated ions and provide a signature that can be matched to reference spectra, either measured from standards or predicted using quantum-chemical calculations.

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Key challenge

Small molecule identification is a key challenge in various areas of (bio)analytical science, including biomarkers, environmental sciences, forensics, etc.

As an example, researchers at FELIX have shown that it is possible to differentiate enantiomeric N-acetylhexosamines directly from body fluids using infrared ion spectroscopy, providing orthogonal identification of molecular structure unavailable by standard liquid chromatography/high-resolution tandem mass spectrometry. These results illustrate the potential for ion spectroscopy to be used for the identification of new functional biomarkers (in this care corresponding to an inborn error of metabolism), and more generally, for the identification of small molecules from complex mixtures.

Recently, we identified new biomarkers for pyridoxine-dependent epilepsy which resulted in a publication in The Journal of Clinical Investigations.

Promising new route

High-performance liquid chromatography mass spectrometry (HPLC/MS) is a widely used analytical technique. FELIX researchers have for the first time used HPLC/MS in combination with infrared ion spectroscopy. We have identified positional isomers of hydroxy-atorvastatins, active metabolites of the drug atorvastatin. In combination with chromatographic separation, infrared spectroscopy of mass-selected ions provides a promising new route for the identification of the molecular structures of unknown m/z peaks in complex mixture analysis. Using currently existing experimental protocols an IR spectrum can routinely be measured from only a few nanograms of sample.

HPLC_IRIS

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