Spectrophotometric determination of copperII in oil sample with 5′-nitro-salicylfluorone

By using the micro-emulsion(CTMAB+n-butyl alcohol+heptane+water) as medium,5′-nitro-salicylfluorone as chromogenic agent,a spectrophotometric determination of trace copper in oil sample has been achieved in KH2PO4-Na2HPO4 buffer system.The maximum absorption wavelength of the complex of copper and the chromogenic agent was 570 nm.Beer's low was obeyed for copper content in the range of 0-9 μg/mL in 25 solution with the apparent molar absorptivity of 1.4×105 L·mol-1·cm-1.The ascorbic acid was used to mask Ni2+,Fe3+,Al3+,etc in the determination.The method has been used to the determination of copper in Daqing crude oil and oil sand with the average recoveries of 99.6% and 97.8%,and the relative standard deviation(RSD) of 0.74% and 0.84%.