Huntley Adam P, Reilly Peter T A
Department of Chemistry, Washington State University, Pullman, Washington, 99164, USA.
J Mass Spectrom. 2021 Feb;56(2):e4703. doi: 10.1002/jms.4703.
Even though sinusoidal quadrupole mass filters have been around for more than 50 years, the relationships defining resolution, resolving power, and transmission from the applied voltages have not been rigorously quantified or discussed. Traditional quadrupole mass filter theory implies that voltages are scanned at constant direct current (DC) to alternating current (AC) voltage ratios with the scanline passing through the origin of the voltage stability diagram. A prominent feature of constant voltage ratio scans is constant baseline theoretical resolving power (m/Δm) that is the same for all masses. Commercial quadrupole instruments rarely scan at constant resolving power because ion transmission increases with mass. Instead, they scan at constant resolution, meaning that the mass window width is fixed. Constant resolution mass scans are preferred because ion transmission does not change with mass. Commercial mass filter systems create constant resolution scans by linearly changing the DC and AC voltages at a fixed ratio in the presence of an additional negative DC voltage offset. This manuscript systematically quantifies the effects of the DC and AC voltages on resolution, resolving power, pseudopotential well depth, and transmission. To quantify these properties, recently developed spreadsheet tools that calculate the laboratory frame stability of ions from the matrix solutions of Hill's equation were used. Voltage scanning methods and their effects on theoretically determined transmission and sensitivity will be discussed.
尽管正弦四极质量过滤器已经存在了50多年，但定义分辨率、分辨能力以及与施加电压之间的传输关系尚未得到严格量化或讨论。传统的四极质量过滤器理论表明，电压是以恒定的直流（DC）与交流（AC）电压比进行扫描的，扫描线穿过电压稳定性图的原点。恒定电压比扫描的一个显著特征是基线理论分辨能力（m/Δm）恒定，对所有质量都是相同的。商业四极仪器很少以恒定分辨能力进行扫描，因为离子传输随质量增加。相反，它们以恒定分辨率进行扫描，这意味着质量窗口宽度是固定的。恒定分辨率质量扫描更受青睐，因为离子传输不随质量变化。商业质量过滤器系统通过在存在额外负直流电压偏移的情况下以固定比例线性改变直流和交流电压来创建恒定分辨率扫描。本文系统地量化了直流和交流电压对分辨率、分辨能力、伪势阱深度和传输的影响。为了量化这些特性，使用了最近开发的电子表格工具，该工具根据希尔方程的矩阵解来计算离子在实验室坐标系中的稳定性。将讨论电压扫描方法及其对理论确定的传输和灵敏度的影响。
