Equilibrium sampling through membrane based on a hollow fiber for determination of naproxen and diclofenac in sludge slurry using Taguchi orthogonal array experimental design

Abstract

A three-phase hollow fiber liquid phase microextraction (HF-LPME) method was evaluated for the extraction and preconcentration of naproxen and diclofenac using a polypropylene membrane followed by analysis using HPLC or LC/MS. In this technique, the drugs were extracted into di-n-hexyl ether immobilized in the wall pores of a porous hollow fiber from 50 mL of sludge slurry sample as a donor phase with pH 3, and then back-extracted into the acceptor phase located in the lumen of the hollow fiber. Experimental factors were studied in 16 trials using a Taguchi orthogonal array experimental design with an OA16 (45) matrix. The significance of these factors was investigated using analysis of variance. The extraction time was statistically demonstrated as the main factor for the extraction of naproxen and diclofenac, while ionic strength played the role of the second most important factor for HF-LPME extraction of diclofenac. The method permitted a detection limit of 0.2–0.7 ng g−1 with relative standard deviation values of 3–5%. Enrichment factors of 2,300 for naproxen and 1,400 for diclofenac were achieved. The method was applied to determine naproxen and diclofenac in sewage sludge from sewage treatment plant, Källby (Lund, Sweden).