In-Loop Solid-Phase Microextraction Coupled with High Performance Liquid Chromatography

Abstract

A new in-loop solid-phase microextraction coupled with high performance liquid chromatography was developed for a fast and easy on line extraction, pre-concentration and LC analysis of moderately polar compounds from non-polar solvents. The inner surface of a long and small bore aluminum tube was electrochemically coated by Al₂O₃ and used as a new in-tube SPME device which can be also replaced to the injection loop in LC to achieve automated in-loop SPME-LC analysis. Large volume of n-hexane containing trace amounts of phenol and biphenyl was passed through the loop. The analytes were then desorbed by a small volume of methanol and introduced into chromatographic column. This technique was successfully used to analyses of different groups of moderately polar compounds. In this work, phenol and biphenyl were selected as the model compounds. Effect of various parameters affecting in-loop solid-phase microextraction and chromatographic procedure were investigated. Under the optimum conditions the calibration graph were linear in the range of 10–1000 ng mL⁻¹ and 50–1500 ng mL⁻¹ the detection limits were 2.5 and 8 ng mL⁻¹ for phenol and biphenyl, respectively. The relative standard deviations (RSDs) were < 2.4 and < 4.9% for phenol and biphenyl respectively. Concentration factor obtained for these compounds were more than 100 folds. The prepared SPME capillary tube (loop) is sturdy, inexpensive, and durable, and can be easily coupled with LC.