Konenkov N V, Korolkov A N, Machmudov Marat
Ryazan State Pedagogical University, 390000 Ryazan, Russia.
J Am Soc Mass Spectrom. 2005 Mar;16(3):379-87. doi: 10.1016/j.jasms.2004.11.023. Epub 2005 Jan 21.
Modulation of the voltages applied to a quadrupole mass filter (QMF), either RF or RF and DC, leads to splitting of the stability region into islands of stability. The ion optical properties, such as transmission, resolving power and peak tails of the first upper stability islands have been investigated by numerical simulation of ion trajectories. The dependence of the location of this island on the amplitude of the modulation and the parameter nu = omega/Omega = Q/P where omega is modulation frequency, Omega is main angular radio frequency, and Q and P are integers, is calculated in detail. Different methods of adjusting the QMF resolution are examined. It is found that operation at the upper and lower tips of the stability islands created by amplitude modulation of the RF voltage is preferred, because of the technical simplicity of this method and a reduction of the required separation time. Amplitude modulation improves the performance of a QMF constructed with round rods, in comparison to perfect quadrupole fields. For example, with amplitude modulation of the RF, to reach a resolution of R(0.1) = 1200 requires only about 75 RF cycles of ion motion in a quadrupole field created by round rods.
对施加到四极质量分析器（QMF）的电压进行调制，无论是射频（RF）还是射频与直流（DC）联合调制，都会导致稳定区域分裂成稳定岛。通过对离子轨迹的数值模拟，研究了首个上稳定岛的离子光学特性，如传输率、分辨率和峰尾。详细计算了该岛的位置对调制幅度以及参数ν = ω/Ω = Q/P（其中ω是调制频率，Ω是主角射频，Q和P为整数）的依赖性。研究了调整QMF分辨率的不同方法。结果发现，由于该方法技术简单且所需分离时间减少，因此在由射频电压幅度调制产生的稳定岛的上下尖端处进行操作更为可取。与理想四极场相比，幅度调制提高了由圆形杆构成的QMF的性能。例如，通过射频幅度调制，在由圆形杆产生的四极场中，要达到R(0.1) = 1200的分辨率仅需要约75个射频周期的离子运动。
