Abstract: Equations are presented for the calculation of partition coefficients determined by two-phase FIA. The equations were demonstrated with the injection of 20 µL metoprolol, p-hydroxybenzaldehyde, p-nitrophenol, phenol, propranolol and p-toluidine in CHCl3 or 0.15 M phosphate buffer of pH 5-6 into a carrier stream of CHCl3 or buffer and subsequently mixed in a PTFE reaction coil (2 m x 0.5 mm i.d.). The two phases were pumped at a total flow rate of 0.21-3.7 ml/min and the organic and aqueous phases separated under N2 using 0.2 and 0.22 µm PTFE and poly(vinylidene fluoride) membranes. The absorbance of the separated phases was determined by spectrophotometry. The product of carrier flow rate and peak area RSD was 0.87% (n = 11). Separation efficiencies of 80-90% and 40-50% were obtained for the hydrophobic and hydrophilic membranes, respectively.

Abstract: In the cited flow injection method, analytes (acetic acid, caffeine, p-toluidine, 2,5-dinitrophenol or alprenolol) were dissolved in water and portions (25 µL) were injected into a stream of water which was then segmented with a stream of n-octanol. After passage through an extraction coil, a portion of the aqueous phase was separated with use of a cellulose nitrate/cellulose acetate (0.45 µm) or PVDF (0.22 µm or 0.1 µm) hydrophilic membrane and analyzed spectrophotometrically. The flow injection manifold was similar to that described previously (cf., Talanta, 1994 41, 1377). Partition coefficients were calculated by varying the phase flow rates. A simplified method involving only two measurements is described. The results agreed well with literature values obtained by the shake-flask method and the RSD were 15%. Phase separation efficiencies at various flow rates are tabulated. The assay time was 15 min.