  Long-lived singlet states hold the potential to drastically extend the
lifetime of hyperpolarization in molecular tracers for in-vivo magnetic
resonance imaging (MRI). Such long lived hyperpolarization can be used for
elucidation of fundamental metabolic pathways, early diagnosis, and
optimization of clinical tests for new medication. All previous measurements of
13C singlet state lifetimes rely on costly and time consuming syntheses of 13C
labeled compounds. Here we show that it is possible to determine 13C singlet
state lifetimes by detecting the naturally abundant doubly-labeled species.
This approach allows for rapid and low cost screening of potential molecular
biomarkers bearing long-lived singlet states.
