Determination of furosine in thermally processed foods by hydrophilic interaction liquid chromatography

Furosine, a marker of the impairment of lysine residues in protein, is formed during acid hydrolysis of the Amadori compound generated at the early stage of the Maillard reaction in thermally treated foods. An analytical method is described for the determination of furosine in thermally processed foods. The method entails acid hydrolysis of food, SPE cleanup with a hydrophilic-lipophilic sorbent, and hydrophilic interaction LC separation. The main advantage of the method is the separation of furosine by means of hydrophilic interaction LC analysis, which simply avoids ion-pairing agents during the chromatography for a complete baseline separation, or avoids the use of a metal-free chromatographic device. In addition, by combining microwave hydrolysis with hydrophilic interaction LC, the complete determination of furosine in a food sample takes approximately 25-30 min. The LOD and the LOQ were 0.7 and 2.3 mg/kg, respectively, for furosine, based on S/Ns of 3 and 10, respectively. The recoveries ranged from 94.6 +/- 3.1 to 98.6 +/- 1.7% for spiking levels of 100-1000 mg/kg sample. The method is easy to use and cost-effective, and gave reproducible results for both within-day and day-to-day tests.