A glass capillary based microfluidic electromembrane extraction of basic degradation products of nitrogen mustard and VX from water

In this work, a glass capillary based microfluidic electromembrane extraction (μ-EME) was demonstrated for the first time. The device was made by connecting an auxillary borosilicate glass tubing (O.D. 3 mm, I.D. 2 mm) perpendicular to main borosilicate glass capillary just below one end of the capillary (O.D. 8 mm, I.D. 1.2 mm). It generated the distorted T-shaped device with inlet '1' and inlet '2' for the introduction of sample and acceptor solutions, respectively. At one end of this device (inlet '2'), a microsyringe containing acceptor solution along with hollow fiber (O.D. 1000 μm) was introduced. This configuration creates the micro-channel between inner wall of glass capillary and outer surface of hollow fiber. Sample solution was pumped into the system through another end of glass capillary (inlet '1'), with a micro-syringe pump. The sample was in direct contact with the supported liquid membrane (SLM), consisted of 20% (w/w) di-(2-ethylhexyl)phosphate in 2-nitrophenyl octyl ether immobilized in the pores of the hollow fiber. In the lumen of the hollow fiber, the acceptor phase was present. The driving force for extraction was direct current (DC) electrical potential sustained over the SLM. Highly polar (log P = −2.5 to 1.4) basic degradation products of nitrogen mustard and VX were selected as model analytes. The influence of chemical composition of SLM, extraction time, voltage and pH of donor and acceptor phase were investigated. The model analytes were extracted from 10 μL of pure water with recoveries ranging from 15.7 to 99.7% just after 3 min of operation time. Under optimized conditions, good limits of detection (2-50 ng mL−1), linearity (from 5-1000 to 100-1000 ng mL−1), and repeatability (RSDs below 11.9%, n = 3) were achieved. Applicability of the proposed μ-EME was proved by recovering triethanolamine (31.3%) from 10 μL of five times diluted original water sample provided by the Organization for the Prohibition of Chemical Weapons during 28th official proficiency test.