Liang Z M, Marshall A G
Department of Chemistry, Ohio State University, Columbus 43210.
Anal Chem. 1990 Jan 1;62(1):70-5. doi: 10.1021/ac00200a013.
The area under a correctly phased absorption-mode spectral peak is a direct measure of the number of oscillators (ions, spins, molecules) in Fourier transform spectrometry (ion cyclotron resonance, magnetic resonance, interferometry absorbance). However, phase correction can prove difficult when (as in broad-band Fourier transform ion cyclotron resonance (FT/ICR] detection is considerably time-delayed after excitation. In the absence of noise, Huang, Rempel, and Gross showed that a "complex area" method yields the correct absorption-mode peak area, for an unphased noiseless spectrum. In this paper, we show that the number of oscillators may also be obtained from a least-squares fit to a magnitude-mode (i.e., phase-independent) spectrum. In the presence of noise and in the absence of peak overlap, the magnitude-mode method offers precision superior to that based on magnitude-mode peak height, "complex area", or even direct digital integration of a correctly phased absorption-mode peak, as demonstrated by both theoretical derivation and experimental FT/ICR results. The present method thus appears to offer the best available determination of the relative abundances of ions of different mass-to-charge ratio in FT/ICR mass spectrometry.
在傅里叶变换光谱法（离子回旋共振、磁共振、干涉吸收法）中，相位正确的吸收模式光谱峰下的面积是振荡器（离子、自旋、分子）数量的直接度量。然而，当（如在宽带傅里叶变换离子回旋共振（FT/ICR）中）激发后检测有相当大的时间延迟时，相位校正可能会很困难。在无噪声的情况下，黄、伦佩尔和格罗斯表明，对于未相位校正的无噪声光谱，“复面积”法可得出正确的吸收模式峰面积。在本文中，我们表明振荡器的数量也可通过对幅度模式（即与相位无关）光谱进行最小二乘拟合来获得。如理论推导和FT/ICR实验结果所示，在存在噪声且不存在峰重叠的情况下，幅度模式法的精度优于基于幅度模式峰高、“复面积”甚至对相位正确的吸收模式峰进行直接数字积分的方法。因此，本方法似乎能为FT/ICR质谱法中不同质荷比离子的相对丰度提供最佳测定。
