Analysis of Pesticide Residues in Eggs by Direct Sample Introduction/Gas Chromatography/Tandem Mass Spectrometry

Direct sample introduction (DSI) or “dirty sample injection” is a rapid, rugged, and inexpensive approach to large volume injection in gas chromatography (GC) for semivolatile analytes such as pesticides. DSI of complex samples such as eggs requires a very selective detection technique, such as tandem mass spectrometry (MS−MS), to determine the analytes among the many semivolatile matrix components that also appear. In DSI, the nonvolatile matrix components that normally would contaminate the GC system in traditional injection methods remain in a disposable microvial, which is removed after every injection. For example, 3 μg of nonvolatile residue typically remained in the microvial after an injection of egg extract using the DSI method. This analytical procedure involves the following:  (i) weighing 10 g of egg in a centrifuge tube and adding 2 g of NaCl and 19.3 mL of acetonitrile (MeCN); (ii) blending for 1 min using a probe blender; (iii) centrifuging for 10 min; and (iv) analyzing 10 μL (5 mg of egg ...