Fig. 2.

MRM analysis of butylated NY from urine. The sample preparation was done as described in the Materials and Methods section. The analysis of the mass spectra was done by “Method II”. Briefly, the rest of the DiY analysis was further derivatized as butylated amino acids and then analyzed by LC/MS/MS. The final concentration of the internal standards cocktail including [¹³C₉]NY is 50 nM. The MRMs of 283.2/181.0 show the native NY and the combination of 292.5/189.0 indicate the MRM of the stable internal standard of NY.