Beyond Accelerator Mass Spectrometry: Recent Developments in All-Optical Measurements of Radioisotope Carbon

The environmental impact of non-renewable energy has come under scrutiny, prompting investments in carbon management strategies like renewable fuels. The presence of radiocarbon in biofuel blends can validate their composition for government regulators and quality control. However, such measurements are challenging and costly, requiring accelerator mass spectrometry (AMS) or liquid scintillation counting (LSC), which necessitate extensive preparation, expensive equipment, and highly trained personnel. Significant advancements have been recently made in developing optical methodologies capable of detecting ¹⁴C at part per quadrillion sensitivity, with a smaller footprint, simpler sample preparation, and reduced cost. This review critically examines the benefits and limitations of direct absorption, cavity ringdown spectroscopy, intracavity optogalvanic spectroscopy, and photoacoustic spectroscopy as optical radiocarbon detection systems that may replace accelerator mass spectrometry as the primary gold standard methodology available.