Miniaturised flow-through PLM coupled with spectrophotometric detection for copper(II) speciation in fungicides†

Abstract

Construction of a novel miniaturised Permeation Liquid Membrane (mPLM) set-up is described. A hydrophobic Celgard 2500 membrane with copper(II) carrier separates the source and receiving solutions flowing in the channels on two sides of the membrane. The set-up consists of two half-cells with channel width of 2 mm and depth variable between 100 and 500 µm made of poly(dimethylsiloxane) (PDMS) using a moulding technology. In contrast to most previous constructions, the new mPLM operates in full flow-through mode, in both source and receiving solutions. This allows for on-line and real-time coupling with the detection system, which significantly reduces the time of analysis. In the present set-up a UV/Vis spectrophotometric detection was applied for Cu(II) transport. For this purpose a composition of the receiving solution was optimised to allow for both free metal ion buffering, which is necessary for maintaining the driving force of the transport, and spectrophtometric detection. The applied UV/Vis detection method is linear in the range 2 × 10−6 M – 4 × 10−5 M (R 2 = 0.996) with a detection limit of 10−6 M in the volume of ca 350 µL (including the receiving channels, cuvette and tubing). The relative standard deviation does not exceed 5%. The transport capabilities of the mPLM set-up are demonstrated using four commercial copper-based fungicides: Nordox 75 WG, Miedzian 50 WP, Curzate 49.5 WP and Mag 50 WP.