Mass Discrimination and Analysis in Mass Spectroscopy

质谱基本上涉及中性分子的电离，然后基于它们对质量（m / z）比率进行检测和定量的批量来分组离子化物质。本文讨论了用于区分电离质量片段及其分析的常见可选择。

四极孔分析仪

A quadrupole mass analyzer comprises of four parallel rods assembled in a square shaped arrangement. The ionized molecules are directed through the centre of the square formed by the rods. A combination of DC and RF potentials is applied to the diagonally opposite rods thereby permitting only selected m/z ratio ions to pass and reach the detector. The other ions strike the rods get destroyed and are unable to reach the detector.

Quadrupole systems offer a cost-effective mass discrimination option. The reproducibility is good but other mass analyzers would be required for applications requiring higher resolutions and pulsed ionization sources. Due to their lower cost and simplicity quadrupole systems are found in majority of bench top GC/ MS and LC/MS systems.

磁性扇区分析仪

磁性扇区分析仪利用永磁体或电磁铁的磁场来解析电离的质量片段。磁场以垂直的方向施加到分子离子的流动路径。该字段在圆弧中偏转离子，从而解决不同的质量。通过另外地对磁场进行电离分子来实现更高的分辨率。在“反向几何”布置磁部位之前。电场通常以固定值保持，并且可以改变磁场以扫描不同的质量以对电离的物种充电。较大或更小的M / Z值的离子撞击管并摧毁。

磁性扇区系统提供高度重现性和分辨率以及高动态质量范围。然而，这种系统的尺寸较大，成本较高。理想情况下，这种分析仪可用于精确质量测量和分析物的同位素比例的测定。

飞行时间分析仪

A uniform field is applied to all ions at the same time permitting them to accelerate down the length of the flight tube. Lighter ions travel faster so as to reach the detector before the heavier ones. The mass to charge ratios are discriminated by the time taken to reach the detector. Such arrangements also help detect mass accurately and are well suited for pulsed ionization sources such as MALDI. The systems provide high mass range among different available mass analyzers.

四极离子疏水阀

除了两个端盖之外，离子阱包括圆环电极，除了两个端盖，它们一起形成一个受限的空间，其中离子在电磁场的帮助下被捕获。然后扫描RF和直流电位以依次呈现不同的质量以对准比率碎片以序列到达探测器。

离子陷阱系统用作紧凑型台面批量分析仪。然而，动态范围是有限的，离子物种的定量很差。

质量分析仪提供了自身的特征，可用于不同的质谱分析应用。随后将占用一些典型的应用程序。