Abstract：The energy in microwave plasma torch atomic emission spectrometry (MPT-AES) is supplied by microwave, which is similar to the characteristic of inductively coupled plasma atomic emission spectrometry (ICP-AES). It has some advantages such as high atomization efficiency, rapid analysis speed and simple operation. However, the application researches of this technology is only limited in the optimization of instrumental working conditions at present, and lack of effective solving measures for the interference of some coexisting elements. Argon was selected as carrier gas and working gas. The working conditions for the determination of calcium in crude oil by MPT-AES were investigated. Meanwhile, the influence of coexisting elements on the determination of calcium was discussed. The results showed that the mass concentration of calcium in range of 0.010-6.00 μg/mL was linear to the corresponding emission intensity with correlation coefficient of r=0.999 8 under the following experimental conditions: the analytical line was Ca 393.366 nm, the microwave power was 85 W, the carrier gas flow rate was 1 350 mL/min, and the working gas flow rate was 650 mL/min. The detection limit of calcium was 5.6×10－3 μg/mL. The interference test results indicated that the determination of calcium was not influenced by 7 times (mass concentration) of sodium, 3 times of iron and cobalt, 1 time of magnesium, copper and aluminum. However, 1 time of vanadium and nickel had interference. The tolerant amount of aluminum, cobalt, nickel, magnesium, iron, copper and vanadium could be increased by 5 times using 0.5 mL of 5 g/L EDTA and 0.5 mL of 10 g/L phenanthroline solution. The experimental method was applied to the determination of calcium in crude oil, and the found results were basically consistent with those obtained by flame atomic absorption spectrometry (FAAS). The relative standard deviations (RSD,n=6) were between 1.6% and 2.2%.
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