电感耦合等离子体质谱法测定水中低浓度铁受钙干扰的消除

采用电感耦合等离子体质谱法测定水中小于0.06 mg·L-1铁量时受到共存的钙(40mg·L-1)的严重干扰。经验证,钙的干扰可借以下途径消除:①采用碰撞池和56Fe、57Fe两同位素中的任一种,钙的干扰均可忽略不计。②如采用非碰撞池,则钙的干扰将因铁与其共存钙的质量浓度的不同而变化:(a)当cFe<0.10mg·L-1,cCa<1mg·L-1,并采用57Fe同位素时,钙的干扰可以忽略;(b)当cFe<0.10mg·L-1,cCa>1mg·L-1时,采用两同位素中的任一种都无法克服钙的严重干扰;(c)当cFe>0.10mg·L-1,cCa<5mg·L-1,无论采用同位素56Fe或57Fe,钙的干扰都不明显,而如cCa>5mg·L-1时,则只能用同位素56Fe才可避免钙的干扰。

On the Elimination of Interference of Calcium in the ICP-MS Determination of Iron with Low Concentration in Water

It was found that the ICP-MS determination of cFe<0.06 mg·L-1 in water was interfered seriously by the presence of 40 mg·L-1 Ca2+.It was proved that the interference of Ca2+ could be eliminated by either of the following ways: ① by using the collision cell,no interference by Ca2+ is observed,and either of the isotopes 56Fe or 57Fe can be used;② in case of without using collision cell,the interfernce of Ca2+ is varied according to the mass concentrations of Fe(Ⅲ) and the co-existing Ca2+,i.e.,(a) in case of cFe<0.10 mg·L-1 and cCa<1 mg·L-1,the interference can be neglected by using the isotope 57Fe;(b) when cFe<0.10 mg·L-1 and cCa>1 mg·L-1,the interference is significant by using either of the 2 istopes;(c) when cFe>0.10 mg·L-1 and cCa<5 mg·L-1,the interference can be neglected and either of the 2 isotopes can be used,and when cCa>5 mg·L-1,the interference can be eliminated only by using the isotope 56Fe.