Abstract：Microwave plasma torch atomic emission spectrometry (MPT-AES) is established using a microwave plasma torch (MPT) as the light source, and using argon as the carrier gas and working gas. It can work normally at low excitation power and low operating gas flow, and has many advantages, including fast analysis speed, low operation cost of equipment and simultaneous determination of multiple elements. However, the temperature of working gas in low-power MPT is low, which suffers from weak excitation ability and poor resistance to matrix interference. Aiming at the problem of matrix interference during the determination of calcium by MPT-AES, on the basis that lanthanum salts are employed as the releasing agent in flame atomic absorption spectrometry analysis, the method for the determination of calcium by MPT-AES in the presence of lanthanum salts was investigated. Experimental results showed that the lanthanum salt had significant sensitizing effect on the determination of calcium by MPT-AES. When the mass concentration of lanthanum in testing system was 0.600 mg/mL, the emission intensity of calcium could be increased by 78.6%. The limit of detection decreased from 2.2×10-3 μg/mL to 1.5×10-3 μg/mL, and the allowed amount of coexisting elements was significantly increased. The proposed method was applied for the determination of calcium in crude oil. The relative standard deviation (RSD, n=6) of determination results was less than 4.0%. The measurement results were consistent with those obtained by the flame atomic absorption spectrometry.
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