Direct solid phase microextraction of complex aqueous samples with hollow fibre membrane protection

Abstract

A new approach to solid phase microextraction is described which enables the analysis of high boiling-point and non-volatile analytes in complex aqueous or other liquid matrices. In this approach the fibre of a solid phase microextraction (SPME) device was placed inside a cellulose hollow membrane with a molecular weight cut-off (MWCO) of 18 000 Da. The membrane, forming a concentric sheath around the fibre, allows target analytes, which typically have a molecular weight of less than 1000 Da, to diffuse through while excluding high molecular weight interfering compounds, such as humic acids, which have molecular weights up to several million Da. With the membrane protection, direct SPME was used successfully for extraction of large PAHs, such as chrysene and perylene, from aqueous samples containing humic acids. The initial investigation shows that the membrane protection slows down mass transfer during direct SPME sampling, which can be improved by using higher temperatures or thinner membranes.