Preparation of Liposome-Immunosensor and Its Application to the Determination of 2,4-D in Urine

To prepare the immunosensor, tiposome was prepared, by dissolveing 22 mg of the mixture of solutes of DPPC, cholesterol, DPPG and DPPE (mixed in the mass ratio of 10 to 10 to 1 to 1) in 4 mL of a mixed solvent of chloroform, isopropylether and methanol (6+6+1 by volume). Potassium ferrocyanide solution (0.15 mol·L-1, 1 mL) was added to the liposome and encapsulated by swirling ultrasonically for 5 min at 45 ℃. Then the liposome encapsulated K4Fe(CN)6 solution (1 mL) was crosslinked with 2,4-D-rabbit antibody (10.53 g·L-1, 200 μL) through the action of glutaric dialdehyde solution (0.7+99.3, 2 mL). A self-prepared MWNT′s modified graphite electrode was dipped into 0.05 mol·L-1 liposome-antibody-pyrrole solution, and polymerized by cyclic voltammetry for 10 times in the potential range of 0-0.75 V at the rate of 50 mV·s-1. This immunosensor was used for rapid determination of 2,4-D in urine. Linearity was obtained in the range of 0.05-2.5 mg·L-1, and the detection limits (3S/N) found was 15.4 μg·L-1.