In the present work, a ‘‘mini-column’’ solid-phase extraction system using thallium(III) ion-imprinted polymer particles has been developed both to preconcentrate and determine thallium(III) ions using online flame atomic absorption spectrometry in aqueous solutions. The mini-column was fabricated using a Pyrex glass tube (7 cm length and 3 mm internal diameter) containing 500 mg of thallium(III) ionimprinted polymer particles. The effects of different parameters such as pH, sample flow rate and also the nature and flow rate of eluent, on the extraction process, were thoroughly studied. Under the optimized conditions, the detection limit was found to be 1.5 ng mL -
1. The relative standard deviation for five replicate analyses of 30 ng mL -
1 of thallium(III) was 2.1%. The method was applied in the determination of thallium in a certified reference material and spiked tap water to demonstrate the accuracy, relative recovery and applicability of the presented method. The proposed technique is simple, convenient, selective and efficient. The enrichment factor was calculated to be 125. Introduction

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