Determination of polar priority phenols at parts per trillion levels in water using on-line liquid-solid extraction followed by liquid chromatography with coulimetric detection.

A high-sensitivity method for the determination of polar phenolic compounds in water samples was developed. Water samples were preconcentrated using on-line solid-phase extraction with LiChrolut EN sorbent and afterwards were analyzed by liquid chromatography and dual coulimetric detection. The first electrode was set at low potential (250 mV) for sample clean up whereas the second one was used for analytical purposes. The system could not be used in its reductive form due to the lack of reversibility on the electrochemical behaviour of nitrophenols. Detection limits at part per trillion level were obtained using only 5 ml of water. Additionally, the large cell constant of the coulimetric detector lead to low values of coefficients of variation (+/- 6) when working with river water.