A new system of flow ratiometry having UV detection without a phase separator was developed and applied to the determination of the chloroform/water distribution coefficients (
KD) of phenol and its derivatives. An aqueous solution of analyte and chloroform was delivered independently and merged at various flow ratios (
Rf). The ratio was changed stepwise. Both phases, segmented each other, passed through an extraction coil and were directly led to a flow cell, where the absorbance of each phase was monitored. A wide-bore tubing (2 mm, i.d., 20 cm long) was inserted between the extraction coil and the flow cell in order to coalesce the chloroform segments and/or aqueous segments. Thus formed bigger segments were easily measured. The
KD was calculated from the slopes and the intersections of linear plots of A
−1 vs. Rf, (
ARf)
−1 vs. Rf−1, and
ARf vs. A, where
A is
Ao (absorbance of chloroform phase),
Aa (absorbance of aqueous phase), Δ
A (=
Ao−
Aa) or Σ
A (=
Ao +
Aa). Among them, the plots using Σ
A as
A gave the best results, probably due to a cancellation of the intrinsic errors in the
Ao and
Aa measurements. The method was simple and efficient (< 5 min/determination) with satisfactory precision.
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