HPLC spectrophotometric determination of metal-porphyrin complexes following a preconcentration method by homogeneous liquid-liquid extraction in a water/pyridine/ethyl chloroacetate ternary component system

A new homogeneous liquid-liquid extraction method based on pi-I-dependent phase separation phenomena was developed using a water/pyridine/ethyl chloroacetate ternary solvent system.. The optimum conditions in the procedure were determined as follows: in order to obtain the water-immiscible small phase (approximately 120 yl) of ethyl chloroacetate, hydrochloric acid ([HCl](T) = 1.44 mol dm(-3)) was added to a homogeneous aqueous solution which consisted of water, ethyl chlorolacetate (1 cm(3): 2.0 vol%) and pyridine (5 cm(3): 12.0 vol%), where the final total Volume was 50 cm3. A concentration factor of 10000 (i.e. 50 cm(3) --> 5 mu l) was achieved by adjusting the initial volume of ethyl chloroacetate. The compound alpha, beta, gamma, delta-tetrakis(4-carboxyphenyl)porphine (TCPP) was selected as an extracting chelate reagent. In the extraction of TCPP and metal-TCPP complexes, when the ratio (V-W/V-O) of the Volume in the water phase (V-W) to that in the sedimented phase (V-O) was 500, the distribution ratio (D) and extraction percentage (E%) were TCPP (14700, 96.7%), Cu-TCPP (7440, 93.7%), Zn-TCPP (22200, 97.8%), Mn-TCPP (1070, 68.1%) and Co-TCPP (8760, 94.6%), respectively. This extraction method was applied as preconcentration in HPLC. The simultaneous complex formation condition between TCPP and each metal ion {i.e., accelerator; [pyridine](T) = 0.25 mol dm(-3) and [Hg2+](T) = 2 X 10(-6) mol dm(-3), pH; 9.3, reaction time; 30 min at room temperature} and The HPLC condition of the metal complexes {i.e., column; ODS (4.6 mm i.d. x 250 mm), mobile phase; the mixture (50 w/w%) of acetonitrile and acetic acid-sodium acetate aqueous solution (pH 3.5), flow rate; 0.5 cm(3)/min, detection wavelength; 420 nm} were selected, respectively, All calibration graphs were linear and passed through the origin over the concentration range of 5 x 10(-9) mol dm(-3) to 10(-7) mol dm(-3). The detection limit (3 sigma) reached 1 x 10(-10) mol dm(-3) for Cu(II) and Mn(II) and 5 x 10(-11) mol dm(-3) for Zn(II) and Co(II), respectively. Satisfactory results for the determination of four kinds of metal in river water (standard material in the Japan Society for Analytical Chemistry: JAC 0032) was obtained.