Hannis J C, Muddiman D C
Department of Chemistry, Virginia Commonwealth University, Richmond 23284, USA.
J Am Soc Mass Spectrom. 2000 Oct;11(10):876-83. doi: 10.1016/S1044-0305(00)00160-4.
A dual electrospray ionization (ESI) source employed with hexapole accumulation and gated trapping provides a novel method of using an internal standard to achieve high mass accuracies in Fourier transform ion cyclotron resonance mass spectrometry. Two ESI emitters are sequentially positioned in front of the heated metal capillary inlet by a solenoid fitted to an XYZ micromanipulator; one emitter contains the analyte(s) of interest and the other an internal standard. A 5 V transistor-transistor logic pulse from the data station controls the solenoid by means of a solid-state relay so that matching of spectral peak intensities (i.e., analyte and internal standard intensities) can be accomplished by adjusting the hexapole accumulation time for each species. Polythymidine, d(pT)18, was used as the internal standard for all studies reported here. The absolute average error for an internally calibrated 15-mer oligonucleotide (theoretical monoisotopic mass = 4548.769 Da) was -1.1 ppm (external calibration: 41 ppm) with a standard deviation of +/-3.0 ppm (external calibration: +/-24 ppm) for a total of 25 spectra obtained at various hexapole accumulation time ratios. Linear least squares regression analysis was carried out and revealed a linear dependence of the magnitudes of the peak height ratios (analyte/internal standard) vs. hexapole accumulation time ratios (analyte/internal standard) which is described by the following equation: y = 0.45 x - 0.02. The fitted line had a %RSD of the slope of 28% with an R2 of 0.93. The applicability of this methodology was extended to a polymerase chain reaction product with a theoretical average molecular mass of 50,849.20 Da. With the internal standard, d(pT)18, an absolute average error of -8.9 ppm (external calibration: 44 ppm) based on five measurements was achieved with a standard deviation of 11 ppm (external calibration: +/-36 ppm), thus illustrating this method's use for characterizing large biomolecules such as those encountered in genomics and proteomics related research.
采用六极杆积累和门控捕获的双电喷雾电离（ESI）源提供了一种在傅里叶变换离子回旋共振质谱中使用内标实现高质量准确度的新方法。两个ESI发射器通过安装在XYZ微操纵器上的螺线管依次放置在加热的金属毛细管入口前；一个发射器含有感兴趣的分析物，另一个含有内标。来自数据站的5V晶体管-晶体管逻辑脉冲通过固态继电器控制螺线管，以便通过调整每种物质的六极杆积累时间来实现光谱峰强度（即分析物和内标强度）的匹配。聚胸腺嘧啶，d(pT)18，用作本文报道的所有研究的内标。对于一个内部校准的15聚体寡核苷酸（理论单同位素质量 = 4548.769 Da），在不同六极杆积累时间比下获得的总共25个光谱的绝对平均误差为-1.1 ppm（外部校准：41 ppm），标准偏差为±3.0 ppm（外部校准：±24 ppm）。进行了线性最小二乘回归分析，结果表明峰高比（分析物/内标）的大小与六极杆积累时间比（分析物/内标）呈线性相关，由以下方程描述：y = 0.45 x - 0.02。拟合线的斜率%RSD为28%，R2为0.93。该方法的适用性扩展到了理论平均分子量为50,849.20 Da的聚合酶链反应产物。使用内标d(pT)18，基于五次测量获得的绝对平均误差为-8.9 ppm（外部校准：44 ppm），标准偏差为11 ppm（外部校准：±36 ppm），从而说明了该方法在表征大型生物分子（如基因组学和蛋白质组学相关研究中遇到的那些）方面的用途。
