Ammonium acetate was used for pH adjustment aiming formation of the [Cu(BCA)2]3− complex and neither analytical or reference sig-nals were significantly affected for concentrations within 0.2 and 1.2 mol L−1.
Four sampling cycles of the acceptor stream (R1plus R2) yielded an absorbance value close to 1.0 for the reference signal, thus maximizing the linear response range with minimum error in the spectrophotometric measurement.