Dual wetting-film multi-syringe flow injection analysis extraction - Application to the simultaneous determination of nitrophenols

A dual wetting-film extraction/back-extraction system based on a multi-syri nge flow injection analysis (MSFIA) set-up coupled to additional burettes a nd solenoid valves is proposed. The system performs on-line analyte extract ion from an aqueous medium to an organic solvent based on the differential flow velocities of the aqueous and organic phases into PTFE tubing, which i s due to the formation of a thin and pseudo-stationary organic film adhered to the inner walls of the extraction coil. The pre-concentrated analytes a re eluted into a small eluting solution segment and conducted to a diode-ar ray spectrophotometer for analysis. The peak maximum spectrum is used for t he simultaneous determination of different analytes by using multi-componen t analysis with multi-linear regression (MLR). This dual system is applied to the multi-component determination of 2, 3- a nd 4-nitrophenol. By using 8 mi of sample and 88 mul of 1-chloroburane in l -octanol (66/34, v/v) as organic phase, a sample throughput of 11 analyses per hour can be obtained. The detection limits for 2-, 3- and 4-nitrophenol are 0.11, 0.46 and 0.07 muM, respectively, and the relative standard devia tions are less than 4%. (C) 2001 Elsevier Science B.V. All rights reserved.