OPERATION OF A QUADRUPOLE ION TRAP MASS-SPECTROMETER TO ACHIEVE HIGH MASS CHARGE RATIOS
OPERATION OF A QUADRUPOLE ION TRAP MASS-SPECTROMETER TO ACHIEVE HIGH MASS CHARGE RATIOS
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DOI：
10.1016/0168-1176(91)85013-c
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发表时间：
1991-05-15
期刊：
影响因子：
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通讯作者：
HEMBERGER, PH
中科院分区：
文献类型：
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作者：
KAISER, RE;COOKS, RG;HEMBERGER, PH
商用四极离子阱质谱仪的主要限制之一是质荷比限值相对较低（每电荷 650 Da）。这一限制限制了解吸电离技术的应用，该技术可以产生每电荷数千Da的离子。提出了几种扩展四极离子阱的质量/电荷范围的技术。这些包括（i）使用较小的电极，（ii）在较低射频下操作，以及（iii）使用适当频率的电压进行共振离子喷射，在质量扫描期间对称地施加在端盖电极上。使用碱金属卤化物盐的外部电离与 Cs+ 轰击来比较每种方法的性能。特别关注扫描速率对分辨率的影响，并描述了一种在不丢失数据的情况下降低扫描速率的方法。对质量测量精度进行了一些详细研究，对使用共振喷射发生的质量偏移进行了表征，并将该信息用于校正质量分配。评估了三种质量范围扩展方法的相对优点。这里使用的特定较小电极中的场不均匀性显然会导致这些设备的一些性能损失，使它们成为最不成功的方法。频率降低可在有限的 m/z 值范围内提供出色的结果。然而，共振喷射可以单独使用来实现更大的 m/z 扩展，并且是选择的（单一）方法。适度的尺寸和频率降低与轴向调制的结合可能是高质量生物质谱的理想解决方案。通过记录 CsI 簇和肽上的数据来说明高质量下的性能。这些实验表明，无需外部校准，质量/电荷测量的精度优于 0.1%，质量分辨率达到 3000 FWHM（单位分辨率为 50% 谷值至 3000），每次充电的质量/电荷范围超过 70 000 Da。
One of the principal limitations of the commercial quadrupole ion trap mass spectrometer is the relatively low limiting value of mass/charge ratio (650 Da per charge). This constraint limits applications of desorption ionization techniques which can produce ions of many thousand Da per charge. Several techniques for extending the mass/charge range of the quadrupole ion trap are presented. These include (i) the use of smaller electrodes, (ii) operation at lower radio frequencies, and (iii) resonance ion ejection using a voltage of appropriate frequency, applied symmetrically across the end-cap electrodes during the mass scan. The performance of each of these methods is compared using external ionization of alkali halide salts with Cs+ bombardment. Special attention is given to the effects of scan rate on resolution and a method of reducing the scan rate without loss of data is described. Mass measurement accuracy is studied in some detail, the mass shifts which occur using resonance ejection are characterized and this information is used to correct mass assignments.The relative merits of the three methods of mass range extension are assessed. Field inhomogeneities in the particular smaller electrodes used here apparently cause some loss of performance in these devices making them the least successful of the methods. Frequency reduction gives excellent results over a limited range of m/z values. However, resonance ejection can be used alone to achieve an even greater m/z extension and is the (single) method of choice. A combination of modest size and frequency reduction with axial modulation is probably an ideal solution for high mass biological mass spectrometry. Performance at high mass is illustrated by recording data on CsI clusters and on peptides. These experiments show that mass/charge measurements are accurate to better than 0.1% without external calibration, that a mass resolution of 3000 FWHM is achieved (unit resolution at 50% valley to 3000), and that a mass/charge range in excess of 70 000 Da per charge is accessible.