基于FAIMS谱图峰位置的离子迁移率非线性函数解析

摘要

离子迁移率的非线性函数反映了物质本身的微观碰撞特性,是FAIMS技术实现离子分离检测的基础.现有的离子迁移率非线性函数求解方法多是近似求解,存在较大误差.该工作提出了一种基于半正弦分离电压和FAIMS谱图峰位置下的严格求解方法,推导出严格的二阶、四阶系数求解方程.利用自制的高场不对称波形离子迁移谱仪分别对乙醇、间二甲苯和正丁醇三种典型的醇和苯类物质进行检测,获取了三种物质的FAIMS谱图,通过谱图峰位置获得了不同分离电压值下的补偿电压,利用最小二乘法求出三种离子非线性函数二阶、四阶系数.拟合后的均方误差表明FAIMS非线性函数严格求解的方法,明显优于现有的求解方法.有助于提高FAIMS检测分辨率,进而有助于建立更加准确的FAIMS图谱,实现FAIMS对检测物质的精准识别.%FAIMS's ion separation mechanism is based on analyte's characteristic nonlinear relationship between its ion mobility and applied electric field strength. Present characterization methods for this nonlinear relationship are based on precarious assumptions which incur substantial errors under many circumstances. A rigorous method for solving the second and fourth taylor series coefficient of this relationship based on dispersion voltage value (assuming half-sinusoidal waveform) and associated compensation voltage value of spectrum peak is presented, alongside with rigorous analytical functions. FAIMS spectrums were obtained for ethanol, metaxylene and n-butanol using custom-built FAIMS spectrometer, and corresponding second and fourth taylor series coefficients were obtained with the proposed method. Evaluation shows that this method substantially reduces the RMS error between interpolated and measured peak compensation voltage values under different dispersion voltages, confirming its superiority over present methods. This rigorous method would help improve spectral resolutions of FAIMS spectrometer, facilitating high precision FAIMS spectrum database construction and accurate analyte discrimination.