No critical pairs were identified among bisphenols and PFC
allocated into HPLC run due to the complete spectral resolution of
the analytes. Mobile phase solvents (acetonitrile and methanol)
and additives (0.1% formic acid, 0.1% acetic acid, 2 mmol/l ammonium
formate and 2 mmol/l ammonium acetate) were examined in
a full factorial experiment, since the published literature lacks
general agreement. H. Gallart-Ayala et al. (2010) recommended
methanol mobile phase containing no additives in order to avoid
ion suppression of BPA. On the other hand, the signal of BPA was
reported to increase after the addition of acetic acid into acetonitrile
mobile phase (Perez-Palacios et al., 2012) or ammonium acetate
into methanol mobile phase (Chu, Haffner, & Letcher, 2005)
which is consistent with our results (Fig. 5). Consequently, the
highest signals of three studied bisphenols, on average, were obtained
with ammonium acetate, no matter what the solvent was.