CONTINUOUS-FLOW METHOD FOR THE DETERMINATION OF PHENOLS AT LOW-LEVELSIN WATER AND SOIL LEACHATES USING SOLID-PHASE EXTRACTION FOR SIMULTANEOUS PRECONCENTRATION AND SEPARATION

Phenols in waters and soil leachates were selectively determined down to sub-ng ml(-1) levels by a continuous-flow spectrophotometric method . The analytes were preconcentrated and separated from the sample matr ix by on-line absorption onto a commercially available absorbent colum n (Amberlite XAD-4) at pH 2.0 in a flow system. Aromatic amines potent ially interfering with detection were not retained and thus posed no p roblem. Retained analytes were eluted by continuously pumping an aqueo us stream at pH 13.0, the eluent being directly introduced into the de termination flow system (4-aminoantipyrine method). The reaction produ ct was subsequently extracted into the organic phase (chloroform) for detection after continuous liquid-liquid extraction, which made the ov er-all assay very sensitive. The calibration graph was linear over the range 0.5-60 ng ml(-1) and the detection limit was 0.2 ng ml(-1). A t hroughput of 8 samples h(-1) was achieved for a preconcentration time of 5 min.