Accelerator Mass Spectrometry Targets of Submilligram Carbonaceous Samples Using the High-Throughput Zn Reduction Method

The high-throughput Zn reduction method was developed and optimized for various biological/biomedical accelerator mass spectrometry (AMS) applications of mg of C size samples. However, high levels of background carbon from the high-throughput Zn reduction method were not suitable for sub-mg of C size samples in environmental, geochronology, and biological/biomedical AMS applications. This study investigated the effect of background carbon mass (mc) and background 14C level (Fc) from the high-throughput Zn reduction method. Background mc was 0.011 mg of C and background Fc was 1.5445. Background subtraction, two-component mixing, and expanded formulas were used for background correction. All three formulas accurately corrected for backgrounds to 0.025 mg of C in the aerosol standard (NIST SRM 1648a). Only the background subtraction and the two-component mixing formulas accurately corrected for backgrounds to 0.1 mg of C in the IAEA-C6 and -C7 standards. After the background corrections, our high-throughput Zn reduction method was suitable for biological (diet)/biomedical (drug) and environmental (fine particulate matter) applications of sub-mg of C samples (> or = 0.1 mg of C) in keeping with a balance between throughput (270 samples/day/analyst) and sensitivity/accuracy/precision of AMS measurement. The development of a high-throughput method for examination of > or = 0.1 mg of C size samples opens up a range of applications for 14C AMS studies. While other methods do exist for > or = 0.1 mg of C size samples, the low throughput has made them cost prohibitive for many applications.