Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA.
Rapid Commun Mass Spectrom. 2012 Sep 15;26(17):1985-92. doi: 10.1002/rcm.6309.
Polycyclic aromatic hydrocarbons (PAHs) are nonpolar and difficult to detect by desorption electrospray ionization. We present a new detection method based on cationization with silver ions, which has the added advantage of being able to differentiate PAHs with the same mass but different structure.
9,10-Diphenylanthracene and triptycene, in addition to four different groups of PAH isomers: (1) anthracene and phenanthrene, (2) pyrene and fluoranthene, (3) benz[a]anthracene, benz[b]anthracene (tetracene), and chrysene (4) benzo[a]pyrene and benzo[k]fluoranthene, were deposited on a paper surface and bombarded with methanol droplets containing silver nitrate. The resulting microdroplets entered a quadruple mass spectrometer for mass analysis.
The mass spectrum shows PAH, Ag + OH + PAH, and Ag(PAH)(n) (n = 1, 2) (and PAH + O(2) in the case of benz[b]anthracene) ions. PAHs having a bay structure, such as phenanthrene, showed a different tendency to interact with silver ions from those PAHs having a linear arrangement of the fused benzene rings, such as anthracene. The ratios of the PAH peak intensity to that of Ag-PAH, Ag + OH + PAH, Ag(PAH)(2), and PAH + O(2) were used to differentiate the PAH isomers sharing the same molecular formula with different structures. For isomeric mixtures the PAH to Ag + OH + PAH ratio was found to be the most useful parameter. The uncertainty in the mole fraction of an isomeric mixture was ±0.09, ±0.13, ±0.25, and ±0.1 for phenanthrene-anthracene, fluoranthene-pyrene, benz[a]anthracene-chrysene, and benzo[a]pyrene-benzo[k]fluoranthene, respectively.
A simple method has been developed for the detection of PAHs in desorption electrospray ionization mass spectrometry based on Ag(I) cationization. The method showed a capability to differentiate PAHs isomers (having the same molecular mass) in isomeric mixture with an uncertainty in the mole fraction of about ±0.1. At high inlet temperature and voltage, this method showed better sensitivity but less ability to differentiate between isomeric species.
多环芳烃（PAHs）是非极性的，难以通过解吸电喷雾电离检测。我们提出了一种新的检测方法，基于与银离子的阳离子化，其优点是能够区分具有相同质量但不同结构的 PAHs。
9,10-二苯基蒽和苝，以及四组不同的 PAH 异构体：（1）蒽和菲，（2）芘和荧蒽，（3）苯并[a]蒽、苯并[b]蒽（并四苯）和䓛，（4）苯并[a]芘和苯并[k]荧蒽，沉积在纸表面上，并与含有硝酸银的甲醇液滴撞击。所得微滴进入四极杆质谱仪进行质量分析。
质谱显示PAH、Ag + OH + PAH和Ag(PAH)(n)（n=1，2）（以及苯并[b]蒽情况下的PAH + O(2)）离子。具有海湾结构的 PAHs，如菲，与具有线性排列的稠合苯环的 PAHs（如蒽）相比，与银离子相互作用的趋势不同。具有相同分子式但结构不同的 PAH 异构体，使用PAH峰强度与Ag-PAH、Ag + OH + PAH、Ag(PAH)(2)和PAH + O(2)的比值进行区分。对于异构体混合物，发现PAH与Ag + OH + PAH的比值是最有用的参数。对于具有相同分子式的异构体混合物，其摩尔分数的不确定度分别为±0.09、±0.13、±0.25 和±0.1，用于菲-蒽、荧蒽-芘、苯并[a]蒽-䓛和苯并[a]芘-苯并[k]荧蒽。
基于 Ag(I)阳离子化，开发了一种用于解吸电喷雾电离质谱中 PAHs 检测的简单方法。该方法具有区分异构体混合物中（具有相同分子量）的 PAHs 异构体的能力，其摩尔分数的不确定度约为±0.1。在高入口温度和电压下，该方法显示出更好的灵敏度，但区分异构体的能力较弱。
