Extraction and preconcentration of manganese(II) from biological fluids (water, milk and blood serum) using supported liquid membrane and membrane probe methods

A supported liquid membrane (SLM) technique was investigated to extract and preconcentrate Mn(II) from water, milk and blood serum. Di-2-ethylhexyl phosphoric acid (DEHPA) with kerosene as diluent was used as a carrier in the membrane to transport Mn(II) from the donor side to acceptor side. The membrane was modified with tri-n-octylphosphine oxide (TOPO) to increase its polarity. Various parameters were investigated to optimise the extraction efficiency: pH of the donor and acceptor phase, dilution factor, donor flow rate. Scanning electron microscope images of the membranes revealed that some matrix compounds were deposited on the surface, thus limiting the extraction process. The optimum conditions found were: pH 3 in the donor phase, 0.2 M nitric acid in the acceptor phase, donor flow rate between 1.0 and 0.3 ml min⁻¹, 15% (w/v) DEPHA and 10% TOPO in kerosene as a carrier in membrane, and dilution factors of 20 times for blood serum and 30 times for milk. The extraction efficiencies were found to be low but constant and highly reproducible showing, strong dependence on sample matrix. The new SLM extraction probe was developed and optimised for Mn(II) extraction. Compared to traditional SLM configurations, this is the simplest configuration. The use of stirring allows the same sample to be extracted many times giving higher extraction efficiency and to minimise the sample size. Adsorptive stripping voltammetry (AdSV) was applied to measure Mn(II) concentration. The optimised method was used to determine the concentration of Mn(II) in water, milk and blood serum samples.