High-performance liquid chromatographic–spectrophotometric determination of copper(II) and palladium(II) with 5,10,15,20-tetrakis(4N-pyridyl)porphine following homogeneous liquid–liquid extraction in the water–acetic acid–chloroform ternary solvent system

The homogeneous liquid–liquid extraction method based on the pH dependent phase-separation phenomenon was studied in the water–acetic acid–chloroform ternary solvent system. The optimum conditions were determined as follows, i.e. in order to obtain a water-immiscible small phase (approximately 50 μl) of chloroform, sodium hydroxide ([NaOH]T=1.29 M) was added to a homogeneous aqueous solution which consisted of water, chloroform (0.2 ml, 0.57 vol.%) and acetic acid (2 ml, 5.71 vol.%), where the final total volume was 35 ml. During the extraction of the 5,10,15,20-tetrakis(4N-pyridyl)porphine (TPyP), Cu(II)- and Pd(II)-TPyP complexes, when the volume ratio (VW/VO) between the water phase and organic phase was 700, the distribution ratio (D) and extraction percentage (E%) were TPyP (5600, 88.9%), Cu(II)-TPyP (6000, 90%) and Pd(II)-TPyP (6700, 91%), respectively. This extraction method was applied to the HPLC system. The calibration graphs were linear and pass through the origin over the concentration range of 2×10−8–4×10−7 M for Cu(II) and 5×10−8–8×10−7 M for Pd(II). The relative standard deviations for the central value of the calibration graph were 3.2% for Cu(II) and 3.7% for Pd(II) (10 determinations). Moreover, the detection limits (S/N=3) were 5×10−9 M for Cu(II) and 8×10−9 M for Pd(II).