Electrokinetic Flow Analysis System for the Determination of Phenols in Water by On-line Liquid-Liquid-Liquid Microextraction
An electrokinetic flow analysis(EFA) system was developed for the determination of phenolic compounds in water samples.The analyte preconcentration and matrix clean-up was performed by an on-line liquid-liquid-liquid microextraction(LLLME) unit.The EFA system consisted of one homemade electroosmotic pump and four solenoid valves,which were controlled by a personal computer with a homemade interface card and Visual C program.The obtained conditions were as follows:dodecanol was used as the orginic solvent of liquid membrane supported by a 10 cm×450 μm i.d.polypropylene hollow fiber,10 μL 0.25 mol/L NaOH was the back-extracting solution,a sample flow rate of 2.0 mL/min and 7.5 times through the extraction channel back and forth were chosen in the analysis.When the total phenolic compounds in 1 mL wastewater was determined,the analytical time needed 9 min,the enrichment factor and limit of detection(LOD) were 53 and 3 μg/L respectively,which were much lower than the maximum allowed level in industrial wastewater.The linear concentration ranged from 9.4×10-3 to 5.7 mg/L phenol,which were adopted as a converted concentration for total phenols.When the total phenolic compounds in 6 mL surface water was determined,the analytical time was 49 min,the enrichment factor and LOD were 300 and 0.6 μg/L respectively,which were lower than the maximum allowed level in surface water.The linear concentration ranged from 1.7 ×10-3 to 1.0 mg/L phenol.