The strict detection limits that are required for the quantitation of pesticide residues in food and environmental samples requires the use of very sensitive, selective, and rugged LC/MS/MS technologies. In this application note the benefits of using LC/MS/MS for this type of analysis is described. In particular the role of the collision cell in the MS/MS experiment is addressed. A method for the simultaneous multiresidue screening of 55 pesticides in both soil and leek extracts in less than 15 minutes is described.
Materials and methods
The 55 pesticides are listed in Table 1. Standard solutions (0.1 250
g.L-1 ) are prepared in a mixture of 50/50 (v/v) Water/Acetonitrile.
Leek samples preparation consists of adding 250 ml acetone to 25 gram
of leek. 20 ml of this solution is cleaned up by using liquid/liquid extraction
(2 x 50 ml dichloromethane). After evaporation to dryness the extract
is reconstituted in 2 ml 50/50 (v/v) water/ACN and spiked with a solution
containing 10 g.L-1 of each of the pesticides listed in Table 1. The
soil samples are treated identically with the exception that the acetone
extraction is performed in an acidic environment. HPLC is performed on
a Perkin-Elmer Series 200 system equipped with an Altima column (C18,
5 m, (250 x 2.1 mm). Elution is performed in gradient mode (Solvent A:
water + 10 mM ammoniumformiate + 0.1% formic acid; Solvent B: ACN + 0.1%
formic acid). Liquid flow rate is 200 l.min.-1 Injection volume is 10
l. Mass spectrometry is performed on an API 2000TM LC/MS/MS System, using