PNNL

Abstract

An investigation into the direct method for liquid scintillation counting (LSC) quantification of biogenic fuel content in fuel blendstock is presented. LSC procedures for quench correction, including the use of an instrument internal standard (Quantulus SQP values), color quench curves, and an internal 14C standard spike on samples containing low-level amounts of biogenic gasoline, jet, and diesel mixed with fossil fuel, were compared. Samples were analyzed on both Perkin-Elmer Quantulus and Tri-Carb instruments, and the 14C contents were compared with those determined by accelerator mass spectrometry. These results indicate that both the direct method with internal spike quench correction and the use of a color-quench curve provide accurate results for 1% biogenic fuel blends. Although both chemical and color quenching in fuel samples can reduce the accuracy of direct LSC analysis, color quenching in highly colored samples reduces efficiency significantly more than chemical quenching for a given instrument-derived quench indication, indicating that chemical quench curves are not appropriate for highly colored biofuel/fossil-fuel blended samples.