Bruce J E, Anderson G A, Smith R D
Chemical Sciences Department, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
Anal Chem. 1996 Feb 1;68(3):534-41. doi: 10.1021/ac950823k.
Fourier transform ion cyclotron resonance (FTICR) mass spectrometry offers unparalleled analytical performance in most regards but has a dynamic range of typically no better than 10(2)-10(3). This limitation reportedly arises from two opposing constraints, involving the maximum number of ions that can be effectively trapped (10(6)-10(7)) and the minimum number of ions required to produce a detectable signal (10(2)-10(3)). A potential solution to this dynamic range limitation is presented, based on the application of selected-ion accumulation using quadrupole excitation. We show that lower concentration species can be effectively accumulated in the FTICR trapped ion cell, while the more abundant species are continually removed by the application of quadrupolar excitation in the form of band-limited or "colored" noise waveforms. The result is that "room" is made in the cell for lower abundance species, even during extended accumulation periods. This approach was demonstrated with mixtures of the bovine proteins, insulin, ubiquitin, and cytochrome c. For normal accumulation, the dynamic range was approximately 100. The application of selected-ion accumulation in the form of colored noise allowed the extension by 2 orders of magnitude and the detection of species of 1 x 10(-8) M concentration from a solution also containing another component at 9 x 10(-5) M. With this method, a putative new low abundance variant of bovine insulin was observed, and selected-ion accumulation and subsequent collisionally activated dissociation were used for its identification. Dipolar magnetron excitation was also explored to enhance selected-ion accumulation and was found to reduce the amount of buffer gas required for complete removal of the undesired species by a factor of 5. Further possible improvements are discussed, as are the complications due to the required balance between magnetron and cyclotron damping rates.
傅里叶变换离子回旋共振（FTICR）质谱在大多数方面都具有无与伦比的分析性能，但动态范围通常不超过10² - 10³。据报道，这种限制源于两个相互矛盾的约束条件，涉及可有效捕获的最大离子数（10⁶ - 10⁷）以及产生可检测信号所需的最小离子数（10² - 10³）。基于使用四极杆激发的选择离子积累的应用，提出了一种解决此动态范围限制的潜在方案。我们表明，较低浓度的物种可以在FTICR捕获离子池中有效积累，而更丰富的物种则通过以带限或“有色”噪声波形形式施加四极激发而不断被去除。结果是，即使在延长的积累期内，池中也为较低丰度的物种留出了“空间”。用牛蛋白质胰岛素、泛素和细胞色素c的混合物证明了这种方法。对于正常积累，动态范围约为100。以有色噪声形式应用选择离子积累可将动态范围扩展2个数量级，并能从还含有浓度为9×10⁻⁵ M的另一种成分的溶液中检测到浓度为1×10⁻⁸ M的物种。用这种方法，观察到了一种推测的牛胰岛素新的低丰度变体，并使用选择离子积累和随后的碰撞诱导解离对其进行了鉴定。还探索了偶极磁控管激发以增强选择离子积累，发现可将完全去除不需要的物种所需的缓冲气体量减少5倍。讨论了进一步可能的改进以及由于磁控管和回旋加速器阻尼率之间所需平衡而产生的复杂性。
