Fabrication of three-dimensional printed flow cell for electromembrane extraction of paraquat and diquat

Abstract

In this study, electro-membrane extraction (EME) across a hollow polymer inclusion membrane (HPIM) was performed using a new three-dimensional printed flow-cell equipped with a bubbleless electrode. The sample solutions were introduced continuously into the flow cell during extraction, while the acceptor solution remained stagnant. The HPIM consisted of cellulose acetate (CTA) as the base polymer, tri-(2-ethylhexyl)-phosphate (TEHP) acting as the plasticiser and di-(2-ethylhexyl)-phosphoric acid (D2EHPA) as the carrier. The use of a proposed bubbleless electrode in the experimental setup allowed the use of ultra-high voltage in EME (up to 3000 V) without any interruption due to bubble formation; this cannot be performed with a conventional EME setup. Operation parameters, such as the sample flow rate and sample volume, were comprehensively investigated. Two cationic herbicides were selected as model analytes: paraquat and diquat. These analytes were extracted selectively from the flowing sample stream across the HPIM, and then enriched in 20 μL of the acceptor solution inside the lumen of the hollow membrane. The extracted solutions were then collected using a micro-syringe and subsequently injected into a capillary electrophoresis coupled with UV spectrophotometric detector (CE-UV) for separation and quantification. Under the optimised conditions, the recovery of both paraquat and diquat was in the range of 96.31–104.96% when spiked into the river water sample. The limits of detection of the method for both herbicides were in the range of 0.2–0.3 μg/L with relative standards deviation below 8.3%. The proposed approach was successfully applied to monitor the herbicide content present in the river water sample at sub-ppb level.