Positive identification of PTSO in the samples was obtained when the retention time and mass spectra of the peak obtained matched with those obtained for the PTSO calibration solution at 20 mg L1. PTSO retention time was 13.4 min while PTSO mass
spectra showed the following mass/charge fragments and relative abundance (in percentage); 76 (100%),118 (15%), 89 (7.5%) and 182 (5%).