Determination of avoparcin in animal tissues and milk using LC-ESI-MS/MS and tandem-SPE.

A highly sensitive and selective method using LC-ESI-MS/MS and tandem-SPE was developed to detect trace amounts of avoparcin (AV) antibiotics in animal tissues and milk. Data acquisition using MS/MS was achieved by applying multiple reaction monitoring of the product ions of [M + 3H](3+) and the major product ions of AV-alpha and -beta at m/z 637 --> 86/113/130 and m/z 649 --> 86/113/130 in ESI(+) mode. The calculated instrumental LODs were 3 ng/mL.