Figure 7.

nhPHIP dilution series for a mixture of isoleucine, arginine, aspartic acid and proline. A) Plot of the nhPHIP signal integrals of the high‐field hydrides for the Ir‐IMes complexes of the four amino acids as a function of their analytical concentration. B) Linear dependence of the sum of the integrals of the two diastereomeric complexes as a function of amino acid analytical concentration. The series was acquired at 278 K in the presence of Ir‐IMes catalyst (0.43 mM), pyridine (15 mM) and 5 bar 51 %‐enriched p‐H₂ in 5 vol % D₂O, 95 vol % [D₄]MeOH. The most concentrated sample contained also 2.3 mM NH₄Cl and 11.2 mM NaCl to mimic a 20‐fold diluted urine environment. These compounds were diluted in the same fashion as the amino acids.