Adenosine-5'-triphosphate (ATP) is known as the "molecular currency" for intracellular processes. ATP concentrations range between 1 to 10 mM, with a 1000:1 ratio between ATP and adenosine diphosphate (ADP). ATP aids the regulation of important cellular processes, which include cellular movement, neurotransmission, and ion channel function. Thus, disruption to ATP homeostasis is linked to a number of diseases, including ischemia, Parkinson's disease and hypoglycaemia. The cause of this disruption is often associated with oxidative stress, which involves the production of highly reactive oxygen species and reactive nitrogen species. In particular, peroxynitrite (ONOO -), is a RNS that is known to inhibit ATP production by oxidatively deactivating mitochondrial ATP synthase. Several other studies have revealed a correlation between ATP and ONOO -concentrations to a range of pathological processes. Therefore, the development of a chemical tool that allows the real time monitoring of these species simultaneously in vitro and in vivo would be highly desirable.