2005 Volume 53 Issue 4 Pages 374-377
The chloroform/water distribution coefficients (KD) of sixteen diazine compounds were determined by a stepwise flow ratiometry. An aqueous solution of analyte was delivered and merged with chloroform. The flow rate ratio of both the phases was varied stepwise under a constant total (chloroform+aqueous) flow rate. The analyte was extracted to chloroform while both the phases, which were segmented by each other, were passing through an extraction coil. The segmented stream was then led to a UV/Vis detector directly without phase-separation. The absorbance of the chloroform and aqueous phases (Ao and Aa, respectively) was each measured at the maximum absorption wavelength of the analyte. The plots of A−1 against Rf, (ARf)−1 against Rf−1, and ARf against A gave straight lines, where A was Ao, Aa or the sum of them (AS). The KD of the analyte was calculated from the slopes and intercepts of the plots. The log KD values obtained for the analytes (−0.5—1.4) were agreed well with the values measured by a shake-flask method. The present method is simple, rapid (5 min/determination) and applicable to the volatile compounds with reasonable precision (standard deviation of log KD<0.07).
