The feasibility of laser-based, detection of carbon-14 at Accelerator Mass Spectrometer (AMS) sensitivities has been demonstrated, but these instruments require large samples sizes and lack compatibility with systems common to biological labs—such as liquid chromatography-mass spectrometry (LC-MS). With their ability to quickly detect and quantify ever smaller amounts of material, LC-MS systems are valued for their capacity to isolate individual biomolecules. As a result, LC-MS coupling is now stipulated for the success and adoption of new biological instrumentation. Consequently, we propose to develop a laser-based, carbon-14 spectrometer for biology using saturated-absorption cavity ring-down spectroscopy (SCARS). This instrument will have similar sensitivity to AMS (~10-15 14C/C limit-of-detection), the ability to handle nanogram to microgram sized samples, and the capability to measure analytes separated by LC systems. This level of carbon-14 sensitivity and the techniques it affords are currently restricted to room-sized AMS instruments that cost millions of dollars and require several dedicated Ph.D. level scientists for operation. The SCAR instrument would be much smaller (table-top sized), cheaper, and easier to operate. The accessibility coupled with the extreme sensitivity of this technology will enable high-throughput, small-sample-size experiments and bring carbon-14 measurements into the modern biological laboratory. This instrument will enhance LC/MS systems—providing a means to quantitatively analyze complex biochemical systems in any research lab. This will have an impact on biology from basic science experiments to more applied human subject studies in drug development.