Using dispersive liquid liquid microextraction for extraction and per-concentration of formaldehyde of seawater samples after derivation with dimedone and their determination by spectrophotometery

In this study, a sensitive and economical method is suggested for the rapid determination of formaldehyde in seawater samples. This method is based on the reaction of formaldehyde with 5, 5-di methyl-1, 3-cyclohexane dion (dimedone) in the presence of ammonium acetate. After the reaction of derivative, a mixture of 900 µL of ethanol as a dispersive solvent and 100 µL of chloroform as an extraction solvent was rapidly injected into a water sample containing formaldehyde. Their concentrations were determined spectrophotometrically in micro-cuvettes at 395 nm. Under the optimum conditions, the calibration graph was linear in the range of (0.1-100) µg/L with the detection limit of 0.02 µg/L and limit of quantification of 0.07 µg/L for formaldehyde. Parameters affecting extraction efficiency including pH, type and volume of extraction and disperser solvents, and amount of dimedone, were investigated and optimized. Under the optimum conditions, the linearity of the technique was in the range of 0.1-100.0 µg. L-1 with a detection limit of 0.02 µg. L-1 for the same compound. The relative recoveries of formaldehyde from seawater samples at spiking levels of 10 µg. L-1 were between 97.0-99.4%. The proposed method was successfully applied for the determination of formaldehyde in seawater of Chabahar Bay.