Spectrophotometric Determination of Formaldehyde in Seawater Samples after In-situ Derivatization and Dispersive Liquid-Liquid Microextraction

In this paper, a simple dispersive liquid-liquid microextraction for the extraction and pre-concentration of formaldehyde in seawater samples followed with spectrophotometric is proposed. Formaldehyde was derivatized in situ with acetyl acetone in the presence of ammonium acetate in a single step. Then it was collected into a mixture of ethanol (disperser solvent) and chloroform (extracting solvent). Experimental parameters which have an influence on the extraction, including type and volume of extracting and disperser solvent, pH of sample solution, the concentration of acetyl acetone and ammonium acetate, reaction time and temperature were evaluated and optimized. Under optimal experimental conditions, good linearity was observed in the range of 1-500 μg/L for the analyte with a limit of detection of 0.29 μg/L. The proposed method was applied to the analysis of real seawater samples. For spiked samples, good recoveries in the range of 97.7-101.5% were obtained. The relative standard deviations were below 2.1%. Using this method, formaldehyde content in seawater from several locations in Chabahar Bay (southeast Iran) were determined in the range of 1.4 to 4.8 μg/L.