Method of producing a composition, composition and its use

A method for producing a liquid composition comprising hyperpolarised 13C-pyruvate said method comprising

• a) forming a liquid mixture comprising a radical of formula (I), 13C-pyruvic acid and/or 13C-pyruvate and freezing the mixture;
• where
• M represents hydrogen or one equivalent of a cation;
• and
• R1 which is the same or different represents a straight chain or branched hydroxylated and/or alkoxylated C1-C4-hydrocarbon group
• b) enhancing the 13C nuclear polarisation of pyruvic acid and/or pyruvate in the mixture via DNP;
• c) adding a buffer and a base to the frozen mixture to dissolve it and to convert the 13C-pyruvic acid into a 13C-pyruvate to obtain a liquid composition or, when only 13C-pyruvate is used in step a), adding a buffer to the frozen mixture to dissolve it to obtain a liquid composition, wherein the buffer is selected from the group consisting of phosphate buffer, ACES, PIPES, imidazole/HCI, BES, MOPS, HEPES, TES, TRIS, HEPPS and TRICIN;
• and
• d) optionally removing the radical and/or reaction products thereof from the liquid composition.