GC-MS Determination of Residual Amount of Clenbuterol in Pork

Pork sample was extracted under alkaline condition with ethyl acetate and back-extracted with HCl solution as described in NY/T 468-2006. The solution obtained was adjusted to pH 4.5 and purified by passing through SCX SPE column. After adding 40 μL of 1.6 mg·L-1 metoprolol solution as internal standard, the sample solution was evaporated to dryness by N2-blowing in a water bath at 60 ℃, 200 μL of toluene and 100 μL of BSTFA were added to the residue, and derivatized for 1 h in an oven at 80 ℃. After cooling, 200 μL of toluene were added, and derivates in the solution were separated on DB-5MS capillary column. MS determination was performed under SIM mode and quantification was carried out by the internal standard method. The monitoring ions of m/z 86 (as quantitative ion) and of m/z 262, 243 and 187 (as qualitative ions) were selected in the analysis. Linearity range for clenbuterol was kept between 16 μg·L-1 and 512 μg·L-1, and detection limits (3S/N) found was 1.0 μg·kg-1. On the base of blank sample, test for recovery was made by standard addition method, giving values of recovery in the range of 79.7%-86.6%, with values of RSD′s (n=6) in the range of 4.8%-6.7%.