| Summary: | In the present paper, the liquid–liquid micro extraction of 4-tert-butylphenol from aqueous solution to trioctyl phosphate organic phase in carbon paste electrode was studied by potentiometry and semi-empirical quantum chemistry with MOPAC2009. The extraction dynamic process was monitored by open circuit potential method, which follows an exponential association function with the apparent first extraction kinetic rate constant of 0.01685 s−1. The Nernstian plot of potential difference of the open circuit potentials against logarithm of 4-tert-butylphenol concentration at 500 s extraction time gives a slope of 0.01382, and indicates that 3 or 4 of 4-tert-butylphenol molecules can be extracted by one cluster of trioctyl phosphate dimer. This equation can also serve as working curve for the determination of 4-tert-butylphenol in the concentration range of 1.0 × 10−4–5.0 × 10−7 M with detection limit of 5.0 × 10−7 M (n = 3, ratio of signal/noise = 3). The semi-empirical quantum chemical calculation offers a thermodynamic evidence for the molecular mechanism of the liquid–liquid micro extraction of 4-tert-butylphenol from aqueous solution to trioctyl phosphate cluster.
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