Hyperpolarisation of Mirfentanil by SABRE in the presence of heroin.

Mirfentanil, a fentanyl derivative that is a 𝜇-opioid partial agonist, is hyperpolarised via Signal Amplification By Reversible Exchange (SABRE), a para -hydrogen-based technique. [Ir(IMes)(COD)Cl] (IMes = 1,3- bis (2,4,6-trimethylphenyl)imidazole-2-ylidene, COD = cyclooctadiene) was employed as the polarisation transfer catalyst. Following polarisation transfer at 6.5 mT, the pyrazine-protons were enhanced by 78-fold (polarisation, P=0.04%). The complex [Ir(IMes)(H)2(mirfentanil)2(MeOH)] + is proposed to form based on the observation of two hydrides at δ -22.9 (trans to mirfentanil) and -24.7 (trans to methanol). In a mixture of mirfentanil and heroin, the former could be detected using SABRE at concentrations less than 1% w/w. At the lowest concentration analyzed, the amount of mirfentanil present was 0.18 mg (812 𝜇M) and produced a signal enhancement of -867-fold (P=0.42%). following polarisation transfer at 6.5 mT.