Synthesis of three N-nitroso dipeptides N-terminal in proline and a method for their determination in food

The terminal N-nitroso derivatives of L-prolyl-L-alanine, L-prolylglycine and L-prolyl-4-hydroxy-L-proline have been synthesized and characterized. A procedure suitable for their analysis in biological samples has been developed and is based on the preparation of an aqueous extract, extraction into an organic solvent, separation by high-performance liquid chromatography and detection by a chemiluminescence method. The average recovery in all cases was above 69% at the level of 200 micrograms/kg using cured meat as a food matrix; the detection limit was 10 micrograms/kg.