2.5.1. MRM — determination of 180 pesticide residues using gas
chromatography (GC)
A homogenised sample of 2 g of apples was placed into a mortar
with 4 g of the solid support Florisil and was blended manually. The homogeneousmixture
was transferred into a glass macro-column packed
with anhydrous sodium sulphate (5.0 g) and silica gel (2.5 g). The
analytes were eluted using 15 ml hexane/acetone (8:2, v/v) and 15 ml
hexane/diethyl ether/acetone (1:2:2, v/v/v). The extract was dried
using a rotary vacuum evaporator at a temperature of approximately
40 °C. Then, the eluate was re-dissolved using 2 ml of hexane/acetone
(9:1, v/v). The final solution was transferred into a GC vessel and placed
onto the rack of the autosampler. GC analysis was performed with a
model 7890A Agilent gas chromatograph (Waldbronn, Germany)
equipped with an automatic split/splitless injector and two selective
detectors: electron capture (ECD) and nitrogen–phosphorous (NPD).