Accelerator mass spectrometry best practices for accuracy and precision in bioanalytical 14C measurements

Abstract

Accelerator mass spectrometers have an energy acceleration and charge exchange between mass definition stages to destroy molecular isobars and allow single ion counting of long-lived isotopes such as 14C (t½=5370 years.). ‘Low’ voltage accelerations to 200 kV allow laboratory-sized accelerator mass spectrometers instruments for bioanalytical quantitation of 14C to 2–3% precision and accuracy in isolated biochemical fractions. After demonstrating this accuracy and precision for our new accelerator mass spectrometer, we discuss the critical aspects of maintaining quantitative accuracy from the defined biological fraction to the accelerator mass spectrometry quantitation. These aspects include sufficient sample mass for routine rapid sample preparation, isotope dilution to assure this mass, isolation of the carbon from other sample combustion gasses and use of high-efficiency biochemical separations. This review seeks to address a bioanalytical audience, who should know that high accuracy data of physiochemical processes within living human subjects are available, as long as a 14C quantitation can be made indicative of the physiochemistry of interest.