139
An HP 5989B mass spectrometer was applied in the ECNI mode (Hewlett Packard, Palo
Alto, USA). Regular performance optimisation was carried out with
perfhiorotributylamine selecting the mass fragments m/z 283.0, 414.0 and 453.0. The
temperature of the transfer line was 270 °C, of the ion source 200 °C and of the
quadrupole 100 °C. Dichloromethane (99.8 %, Scharlau, Barcelona, Spain)was mixed
with methane at a pressure ratio of 1+4 and a total reagent gas pressure of 200 Pa (1,5
Torr) using a modified reagent gas inlet (Zencak el al., 2003). The most abundant
isotope masses of the [M+Cl]" adducts and of the internal standard 1 ’C io-/ra/7.s-Chlordan
were recorded in the selective ion mode (Zencak et al., 2003).
5.6.8 Quantification of PCAs by EI-MS/MS
Gas chromatographic separations were carried out on a Star 3400 CX gas
chromatograph (Varian, Wallnut Creek, USA) using a capillary of 5 m length and 0.25
mm ID coated with 0.25 pm of DB35-MS (35 % phenyl-methylpolysiloxane, J&W
Scientific, Folsom, USA). A restriction capillary of 9 cm length and 0.05 mm ID was
connected to the outlet to reduce the flow into the ion trap mass spectrometer. The
injector temperature was 250 °C. Helium (99,999 %, Carbagas, Switzerland) was used
as carrier gas at a pressure of 68.9 kPa. The temperature programme was as follows:
100 °C for 1 min, then with 50 °C/min to 300 °C, isothermal for 4 min. Splitless
injections (splitless time 1.5 min) of 2.5 pi sample volume were carried with a Varian
8200 autosampler.
A Saturn 2000 (Varian, Wallnut Creek, USA) ion trap mass spectrometer was
employed. The following EI-MS/MS conditions were applied: Electron energy 70 eV,
filament current 70 pA, scan range m/z 50-300, scan time 0.3 s, maximum ionisation
time 25 ms, isolation time 5 ms and excitation time 20 ms. The selected ions to be
fragmented as well as further parameters are given in Table 44. The precursor ion m/z
383 [M-C1] + and the product ion m/z 276 [M-4C1] + were selected for the internal
standard 1 ’C io-/ra/7.s'-chlordane (excitation amplitude 0.85 V and excitation storage level
m/z 169,0).
