For analysis of the non-polar heterocyclic amines, the same column (ODS80 ToyoSoda TSK gel, 250 × 4.6 mm i.d. with Supelguard LC-18-DB, 20 x 4.6 mm i.d.) and the following HPLC conditions were used; solvent A was 0.01 M triethylamine adjusted to pH 3.6 with acetic acid and solvent B was acetonitrile. For the first 20 min a linear gradient was used (15 30% B in A from 0 to 15min followed by 30-55% B in A from 15 to 20 min).