Electrochemical sensor based on phospholipid modified glassy carbon electrode - determination of paraquat

Electrochemical sensor based on glassy carbon electrode modified with asolectin (mixture of soybean phospholipids) was developed. Properties of phospholipid layer, such as thickness and compactness, were investigated using atomic force microscopy and X-ray photoelectron spectroscopy. Phospholipids completely cover whole surface and the thickness of the layer 7.1 +/- 1.2 nm corresponds to the value of the phospholipid bilayer of cell membranes. Due to the accumulation of paraquat in the phospholipid layer, square wave voltammetry with asolectin modified electrode exhibits three times higher sensitivity, measured as a slope of calibration dependence, and better linearity in comparison to unmodified glassy carbon electrode. Limit of detection 2.2 nmol L-1 and recoveries higher than 88% were achieved in model samples of water. The method was used for determination of paraquat in real sample of river water and results were compared with high performance liquid chromatography and differential pulse voltammetry on hanging mercury drop electrode giving 0.071 +/- 0.010, 0.050 +/- 0.010 and 0.061 +/- 0.008 mu mol L-1, respectively.