微波等离子体炬原子发射光谱法测定铁增敏效应

Sensitization for Determination of Iron by Microwave Plasma Torch Atomic Emission Spectrometry

针对在低功率下工作的微波等离子体炬原子发射光谱法(MPT-AES)存在对一些元素检测灵敏度较低和抗基体干扰能力弱的问题,以氩气为载气和工作气,研究了表面活性剂及镧盐对MPT-AES测定铁的增敏效应,考察了铁测定的工作条件和共存元素对铁测定的影响.实验结果表明,非离子表面活性剂对铁的测定有抑制作用,而阳离子表面活性剂和镧盐对铁的测定有增敏作用,其中镧盐增敏效果最好.以镧盐为增敏剂,不仅可提高MPT-AES测定铁的灵敏度,还可增加共存元素的允许量.当体系中镧浓度为0.500 mg/m L时,至少可使40倍的锌,30倍的钴,20倍的镍、锰,15倍的钙,10倍的镁、铜和钠不影响铁的测定.与不加镧时相比,铁的发射强度提高了2.4倍,检出限由原来的27.5×10^(-3)μg/m L下降为8.5×10^(-3)μg/m L.将本方法应用于原油样品中铁的测定,所得结果与火焰原子吸收光谱法测定结果一致.

The sensitizing effects of surfactant and lanthanum on the determination of iron by microwave plasma torch atomic emission spectrometry（ MPT-AES） were studied to solve the low detection sensitivity and weak resistance to matrix interference under low-power working condition using argon as carrier gas and working gas.The operating conditions and the influence of coexisting elements on the determination of iron were investigated in detail. The results show that the non-ionic surfactant has an inhibiting effect on the determination of iron,while cationic surfactant and lanthanum chloride have a sensitizing effect,and the lanthanum salt shows the best effect. Lanthanum salts used as sensitizer can not only increase the sensitivity of MPT-AES determination of iron,but also increase the allowable amount of coexisting elements. When the concentration of La3＋ in the test system is 0. 500 mg/m L,the determination of iron could not be interfered by at least 40 times of zinc,30 times of cobalt,20 times of nickel and manganese,15 times of calcium,10 times of magnesium,copper and sodium. The emission intensity of iron increased up to 2. 4 times,and the detection limit decreased from27. 5×10-3μg/m L to 8. 5×10-3μg/m L when using lanthanum salts as sensitizer. The method was applied to the determination of iron in crude oil samples,and the measured results agree with that obtained by flame atomic absorption spectrometry.