Wirth Marisa A, Rüger Christopher P, Sklorz Martin, Zimmermann Ralf
1 Joint Mass Spectrometry Centre / Chair of Analytical Chemistry, University of Rostock, Rostock, Germany.
2 Cooperation Group Comprehensive Molecular Analytics, Helmholtz Zentrum München, Neuherberg, Germany.
Eur J Mass Spectrom (Chichester). 2017 Apr;23(2):49-54. doi: 10.1177/1469066717697985. Epub 2017 Mar 20.
Proton sponges are polyamines with high proton affinity that enable gentle deprotonation of even mildly acidic compounds. In this study, the concept of proton sponges as signal enhancing dopants for electrospray ionisation is presented for the first time. 1,8-Bis(dimethylamino)naphthalene (DMAN) and 1,8-bis(tetramethylguanidino)naphthalene (TMGN) were chosen as dopants, using methanol and acetonitrile/methanol as solvents. Individual standard compounds, compound mixtures and a diesel fuel as a complex sample matrix were investigated. Both proton sponges enhanced signal intensities in electrospray ionisation negative mode, but TMGN decomposed rapidly in methanolic solution. Significantly higher signals were only achieved using the acetonitrile/methanol mixture. On average a more than 10-fold higher signal intensity was measured with 10mol l DMAN concentration. A stronger signal increase of alcohol functionalities was observed compared to acid functionalities. All compound classes which were detected in the diesel fuel (CH- and CHO-class) received roughly 100-fold higher signal intensities when using DMAN as a dopant. Furthermore, the number of detected compounds as well as the double bond equivalent of the detected compounds increased. The compound class distribution shifted when adding DMAN and the formerly dominant CHO-, CHO-, and CHO- classes received similar relative intensities as formerly less accessible classes. The findings depict DMAN as a promising additive for electrospray ionisation negative analysis of at least mildly acidic compounds, even within complex sample material.
质子海绵是一类具有高质子亲和力的多胺，能够使即使是轻度酸性化合物也能温和地去质子化。在本研究中，首次提出了将质子海绵作为电喷雾电离信号增强掺杂剂的概念。选用1,8 - 双（二甲氨基）萘（DMAN）和1,8 - 双（四甲基胍基）萘（TMGN）作为掺杂剂，以甲醇和乙腈/甲醇作为溶剂。研究了单一标准化合物、化合物混合物以及作为复杂样品基质的柴油燃料。两种质子海绵在电喷雾电离负离子模式下均增强了信号强度，但TMGN在甲醇溶液中迅速分解。仅使用乙腈/甲醇混合物时才获得了显著更高的信号。在10mol·L DMAN浓度下，平均测量到的信号强度提高了10倍以上。与酸性官能团相比，观察到醇类官能团的信号增强更强。当使用DMAN作为掺杂剂时，柴油燃料中检测到的所有化合物类别（CH类和CHO类）的信号强度提高了约100倍。此外，检测到的化合物数量以及检测到的化合物的双键当量增加。添加DMAN时，化合物类别分布发生了变化，以前占主导地位的CHO - 、CHO - 和CHO - 类别的相对强度与以前较难检测到的类别相似。这些发现表明，DMAN是至少对轻度酸性化合物进行电喷雾电离负离子分析的一种有前途的添加剂，即使在复杂样品材料中也是如此。
