ICP-MS干扰及其去除

ICP-MS是一种用于痕量金属分析的多功能技术，用于从LI（原子质量7）到PPB，子PPB甚至PPT水平的铀（原子质量7）（原子质量250）。但是，像其他任何痕量金属分析一样，ICP-MS也没有干扰。

Types of Interferences

Isobaric Interferences

同位素在样品溶液中与分析物元件相同的质量质量的存在引起的同位素干扰。除了样品溶液中的元素外，还作为消化酸或血浆气体中的杂质存在，并且可以导致同质干扰。最简单的方法是通过从分析物同位素的强度测量干扰元件的强度来进行校正。

多原子或分子干扰

Molecular interferences are due to a combination of sample or matrix ions with Ar and other matrix elements such as O, N, H,C,Cl,etc. Light elements such as Li, B or Be are not affected due to their small mass.

Starting with \(^3^9K\) this type of interference becomes significant for molecular species such as \(^3^9ArH\) and \(^2^3Na^1^6O\). The isotopes \(^5^6Fe, ^3^9K \) and \(^4^0Ca\) can all be interfered with Ar,O and N isotopes. For higher elements, lanthanides in particular, polyatomic interferences result from elements that are 16 atomic mass units lower due to metal-oxide formation. Polyatomic interferences generally cause problems in determination of first row of the periodic table due to large possibility of combination of Ar with matrix components. Collision cells offered by different manufacturers have reduced or even completely removed such interferences.A collision cell is located between ion optics and the mass analyzer. A quadrupole inside the reaction chamber is used to remove polyatomic interferences. Controlled reaction inside the collision cell such as ammonia converts the analyte of interest to another species resulting in removal of interference.

Doubly charged ion interference

Such interferences result from presence of doubly charged isotopes with twice the mass of analyte of interest. An example is interference from \(^2^0^6Pb^+^+\) upon \(^1^0^3Rh\) is likely at high Pb concentrations. Alkaline and rare earth elements form doubly charged ions to a greater extent than others. However, fortunately such interference is not common in Ar plasmas.

空间充电效果

A beam of positively charged ions is subject to mutual repulsion. Lighter elements with lower momentum are lost during lateral movement more than heavier elements. As a result the sensitivity of lower mass elements falls in presence of heavier mass elements. An example is loss of sensitivity of lithium in presence of high concentration of Uranium. On the other hand a high concentration of lithium will not depress Uranium concentration. Such space charge effects can be minimized by measuring the lighter element under reduced concentrations of heavier elements.

在ICP-MS分析中的一般干扰中，可以通过以下方式克服：

• Sample purification for removal of species capable of producing polyatomic interferences.
• 使用空白校正来用于由酸，水和血浆气体产生的多原子。
• Making use of collision cells with appropriate reaction gases