Spectroswiss, EPFL Innovation Park, 1015 Lausanne, Switzerland.
Laboratoire de Chimie Moléculaire, CNRS UMR 9168, Ecole Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau, France.
J Am Soc Mass Spectrom. 2020 Nov 4;31(11):2258-2269. doi: 10.1021/jasms.0c00221. Epub 2020 Oct 5.
Ion signal detection at the true (unperturbed) cyclotron frequency instead of the conventional reduced cyclotron frequency has remained a formidable challenge since the inception of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Recently, routine FT-ICR MS at the true cyclotron frequency has become a reality with the implementation of ICR cells with narrow aperture detection electrodes (NADEL). Here, we describe the development and implementation of the next generation of these cells, namely, a 2xNADEL ICR cell, which comprises four flat detect and four ∼45° cylindrical excite electrodes, enabling independent ion excitation and quadrupolar ion detection. The performance of the 2xNADEL ICR cell was evaluated on two commercial FT-ICR MS platforms, 10 T LTQ FT from Thermo Scientific and 9.4 T SolariX XR from Bruker Daltonics. The cells provided accurate mass measurements in the analyses of singly and multiply charged peptides (root-mean-square, RMS, mass error / of 90 ppb), proteins (/ = 200 ppb), and petroleum fractions (/ < 200 ppb). Due to the reduced influence of measured frequency on the space charge and external (trapping) electric fields, the 2xNADEL ICR cells exhibited stable performance in a wide range of trapping potentials (1-20 V). Similarly, in a 13 h rat brain MALDI imaging experiment, the RMS mass error did not exceed 600 ppb even for low signal-to-noise ratio analyte peaks. Notably, the same set of calibration constants was applicable to Fourier spectra in all pixels, reducing the need for recalibration at the individual pixel level. Overall, these results support further experimental development and fundamentals investigation of this promising technology.
自傅里叶变换离子回旋共振质谱（FT-ICR MS）问世以来，一直存在一个艰巨的挑战，即在真实（未受干扰的）回旋频率下而非传统的降低回旋频率下进行离子信号检测。最近，随着采用窄孔径检测电极（NADEL）的 ICR 池的实施，常规 FT-ICR MS 在真实回旋频率下得以实现。在这里，我们描述了这些细胞的下一代，即 2xNADEL ICR 细胞的开发和实施，它由四个平面检测和四个∼45°圆柱激励电极组成，能够实现独立的离子激励和四极离子检测。在两个商业 FT-ICR MS 平台上，即 Thermo Scientific 的 10 T LTQ FT 和 Bruker Daltonics 的 9.4 T SolariX XR，对 2xNADEL ICR 细胞的性能进行了评估。该细胞在对单电荷和多电荷肽（均方根 RMS 质量误差 / 为 90 ppm）、蛋白质（/ = 200 ppm）和石油馏分（/ < 200 ppm）的分析中提供了准确的质量测量结果。由于测量频率对空间电荷和外部（捕获）电场的影响降低，2xNADEL ICR 细胞在宽捕获电位范围（1-20 V）下表现出稳定的性能。同样，在 13 小时的大鼠脑 MALDI 成像实验中，即使对于低信噪比分析物峰，RMS 质量误差也不超过 600 ppm。值得注意的是，同一组校准常数适用于所有像素的傅里叶谱，减少了在单个像素级别重新校准的需要。总的来说，这些结果支持进一步实验开发和对这项有前途的技术的基础研究。
