Intracavity Optogalvanic Spectroscopy A New Ultra-sensitive Analytical Technique for 14C Analysis

摘要

We show a new ultra-sensitive laser based analytical technique, intracavity optogalvanic spectroscopy, allowing extremely high sensitivity for detection of ¹⁴C labeled carbon dioxide. Capable of replacing large accelerator mass spectrometers, the technique quantifies attomoles of ¹⁴C in submicrogram samples. Based on the specificity of narrow laser resonances coupled with the sensitivity provided by standing waves in an optical cavity and detection via impedance variations, limits of detection near 10^{-15 14}C:¹²C ratios are obtained. Using a 15W ¹⁴CO2 laser, a linear calibration with samples from 10^-15 to >2 × 10^-12 in ¹⁴C:¹²C ratios, as determined by accelerator mass spectrometry, is demonstrated. Possible applications include microdosing studies in drug development, individualized sub-therapeutic tests of drug metabolism, carbon dating and real time monitoring of atmospheric radiocarbon. The method can also be applied to detection of other trace entities.