Fiber optic-linear array detection spectrophotometry in combination with dispersive liquid–liquid microextraction for simultaneous preconcentration and determination of palladium and cobalt Original Research Article

A new combined method including fiber optic-linear array detection spectrophotometry (FO-LADS) and dispersive liquid–liquid microextraction (DLLME) was developed using a cylindrical micro-cell for simultaneous preconcentration and determination of different species. DLLME and FO-LADS methods have good matching conditions for being combined since FO-LADS is a suitable method for the determination of analytes in low volume of the remained phase obtained after DLLME. DLLME technique was successfully used as a sample preparation method. In this preconcentration method, an appropriate mixture of ethanol (the disperser solvent) and 1,2-dichlorobenzene (the extraction solvent) was injected rapidly into the water sample containing palladium and cobalt after complex formation using 1-(2-pyridylazo)-2-naphthol (PAN) reagent. After phase separation, 50 μL of the sedimented phase containing enriched analytes was determined by FO-LADS. The ordinary and first derivative absorption spectra were obtained for optimization and simultaneous determination of palladium and cobalt, respectively. Under the optimum conditions, the calibration graphs were linear in the range of 2–100 μg L−1 and 1–70 μg L−1 with detection limit of 0.25 μg L−1 and 0.2 μg L−1 for palladium and cobalt, respectively. The relative standard deviations (R.S.D.s, n = 5) were lower than 4%. The enhancement factors of 162 and 165 were obtained for palladium and cobalt, respectively. The proposed method was compared with other methods and applied to the analysis of several real and synthetic samples with satisfactory results.