Sensitive analysis of metal cations in positive ion mode electrospray ionization mass spectrometry using commercial chelating agents and cationic ion-pairing reagents.
Sensitive analysis of metal cations in positive ion mode electrospray ionization mass spectrometry using commercial chelating agents and cationic ion-pairing reagents.
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DOI：
10.1002/rcm.6185
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发表时间：
2012-05
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通讯作者：
Edra Dodbiba;Chengdong Xu;Eranda Wanigasekara;D. Armstrong
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文献类型：
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作者：
Edra Dodbiba;Chengdong Xu;Eranda Wanigasekara;D. Armstrong
金属在许多科学和环境领域中发挥着非常重要的作用，因此对其进行检测和分析是非常必要的。本文建立了一种简单、灵敏的正离子模式电喷雾质谱检测金属的方法。金属离子是带正电荷的，因此它们有可能在正离子模式ESI-MS中被检测到；然而，它们的小质量/电荷(m/z)比使它们落在质谱图的低质量区域，这是具有最大背景噪声的区域。因此，它们的检测可能变得极其困难。用电喷雾质谱(ESI-MS)检测金属的一种更好、更广为人知的方法是用络合剂将它们络合。在这项研究中，11种不同的金属，Fe(II)，Fe(III)，Mg(II)，Cu(II)，Ru(III)，Co(II)，Ca(II)，Ni(II)，Mn(II)，Sn(II)和Ag(I)与两种商用的螯合剂：乙二胺四乙酸(EDTA)和乙二胺二丁二酸(EDDS)配对。由于负离子模式ESI-MS与正离子模式ESI-MS相比有许多缺点，因此如果能在正离子模式下检测到这些带负电荷的复杂离子将是非常有利的。本文描述了这种方法，并证明它的灵敏度要低得多。每个带负电荷的金属络合物都与六种阳离子配对试剂配对。在正单离子监测(SIM)和单反应监测(SRM)模式下，用电喷雾质谱(ESI-MS)分析了新的带正电的三元络合物。结果清楚地表明，阳离子试剂的存在显著提高了这些分析物的灵敏度，通常提高了几个数量级。与负离子模式ESI-MS相比，本文开发的用于金属检测的新方法显著提高了检测限(LODS)，并在未来对这些物种和许多其他物种的痕量研究中显示出巨大的潜力。
Metals play a very important role in many scientific and environmental fields, and thus their detection and analysis is of great necessity. A simple and very sensitive method has been developed herein for the detection of metals in positive ion mode ESI-MS. Metal ions are positively charged, and as such they can potentially be detected in positive ion mode ESI-MS; however, their small mass-to-charge (m/z) ratio makes them fall in the low-mass region of the mass spectrum, which has the largest background noise. Therefore, their detection can become extremely difficult. A better and well-known way to detect metals by ESI-MS is by chelating them with complexation agents. In this study eleven different metals, Fe(II), Fe(III), Mg(II), Cu(II), Ru(III), Co(II), Ca(II), Ni(II), Mn(II), Sn(II), and Ag(I), were paired with two commercially available chelating agents: ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS). Since negative ion mode ESI-MS has many disadvantages compared to positive ion mode ESI-MS, it would be very beneficial if these negatively charged complex ions could be detected in the positive mode. Such a method is described in this paper and it is shown to achieve much lower sensitivities. Each of the negatively charged metal complexes is paired with six cationic ion-pairing reagents. The new positively charged ternary complexes are then analyzed by ESI-MS in the positive single ion monitoring (SIM) and single reaction monitoring (SRM) modes. The results clearly revealed that the presence of the cationic reagents significantly improved the sensitivity for these analytes, often by several orders of magnitude. This novel method developed herein for the detection of metals improved the limits of detection (LODs) significantly when compared to negative ion mode ESI-MS and shows great potential in future trace studies of these and many other species.