The selectivity of the method was evaluated by exposing OTC and TC at a concentration level of 250 lgkg, to the
following stress conditions: 0.010 and 0.10 M HCl, 0.010 and 0.10 M NaOH, 3% v/v H2O and temperature (55 C) for 1 h and 0.010 M HCl, 0.010 M NaOH, 3% v/vH2O22 for 24 h