Absolute optical chiral analysis using cavity-enhanced polarimetry

Chiral analysis is central for scientific advancement in the fields of chemistry, biology, and medicine. It is also indispensable in the development and quality control of chiral compounds in the chemical and pharmaceutical industries. Current methods for chiral analysis, namely optical polarimetry, mass spectrometry and nuclear magnetic resonance, are either insensitive, have low time resolution, or require preparation steps, and so are unsuited for monitoring chiral dynamics within complex environments: the current need of both research and industry. Here we present the concept of absolute optical chiral analysis, as enabled by cavity-enhanced polarimetry, which allows for accurate unambiguous enantiomeric characterization and enantiomeric-excess determination of chiral compounds within complex mixtures at trace levels, without the need for calibration, even in the gas phase. The utility of this approach is demonstrated by post chromatographic analysis of complex gaseous mixtures, the rapid quality control of perfume mixtures containing chiral volatile compounds, and the online in-situ observation of chiral volatile emissions from a plant under stress. Our approach and technology offer a step change in chiral compound determination, enabling online quality control of complex chemical mixtures, identification of counterfeit goods, detection of pests on plants, and assessment of chiral emission processes from climate relevant ecosystems.