acetonitrile in water (both containing 0.1% formic acid) over 4 min
at a flow rate of 0.6 ml/min. The column was kept at 40 C and
1.00 ll of the glucosinolate extracts was injected. The samples
were analysed by negative electrospray ionisation and m/z data
from 150 to 1000 were acquired at a scan time of 0.25 s. Capillary
and cone voltages were set at 2.4 kV and 50 V, respectively, whilst
source and desolvation temperatures were set to 120 and 300 C,
respectively. Nitrogen was used as desolvation gas at 450 l/min.
The MS was tuned to a resolution of 10,000 (FWHM) and leucine-
enkapheline was infused through the reference probe for
internal calibration during data aqusition. The peak for each glucosinolate
(accurate mass ±0.05 Da) was integrated and the endogenous
amounts were calculated based on the response of the
internal standard.