Determination of Sulfite in Water and Dried Fruit Samples by Dispersive Liquid-Liquid Microextraction Combined with UV-Vis Fiber Optic Linear Array Spectrophotometry

A simple and rapid dispersive liquid-liquid microextraction (DLLME) method was applied to preconcentrate sulfite ions from aqueous samples as a prior step to its determination by fiber optic-linear array detection spectrophotometry. The procedure is based on the color reaction of sulfite with o-phthaldialdehyde (OPA) in the presence of ammonia to form isoindole and extraction of the formed isoindole derivative using the DLLME technique. The conditions for the microextraction performance were investigated and optimized. The calibration graph was linear in the range of 2-100 mu g L(-1)with a detection limit of 0.2 mu g L-1. The relative standard deviation for five replicate measurements of 10 and 50 mu g L(-1)of sulfite were 2.8 and 2.0 %, respectively. Under the optimized conditions, the enrichment factor of similar to 133 was obtained from a sample volume of 10 mL. The proposed method was successfully applied to the sulfite determination in drinking water and in food samples.