Analysis of Base Oil Fractions by ClMn(H2O)+ Chemical Ionization Combined with Laser-Induced Acoustic Desorption/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

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• 作者：Penggao Duan ; Kuangnan Qian ; Steven C. Habicht ; David S. Pinkston ; Mingkun Fu ; Hilkka I. Kenttä ; maa
• 刊名：Analytical Chemistry
• 出版年：2008
• 出版时间：March 15, 2008
• 年：2008
• 卷：80
• 期：6
• 页码：1847 - 1853
• 全文大小：176K
• 年卷期：v.80,no.6(March 15, 2008)
• ISSN：1520-6882

文摘

Laser-induced acoustic desorption (LIAD), combined withchemical ionization with the ClMn(H₂O)⁺ ion, is demonstrated to facilitate the analysis of base oils by Fouriertransform ion cyclotron resonance mass spectrometry.The LIAD/ClMn(H₂O)⁺ method produces only one product ion, [ClMn + M]⁺, for each component (M) in baseoils, thus providing molecular weight (MW) informationfor the analytes. With the exception of one sample, nofragmentation was observed. The mass spectra indicatethe presence of homologous series of ions differing inmass by multiples of 14 Da (i.e., CH₂). All peaks in thespectra correspond to ions with even m/z values andhence are formed from hydrocarbons with no nitrogenatoms, in agreement with the compositional nature of baseoils. The MW distributions measured for two groups ofbase oil samples cover the range 350-600 Da, which isin excellent agreement with the values determined by gaschromatography. Moreover, the hydrocarbon types (i.e.,paraffin and cycloparaffins with different numbers ofrings) present in each base oil sample can be determinedbased on the m/z values of the product ions. Finally, theresults obtained by using LIAD/ClMn(H₂O)⁺ indicate thatthe efficiency of the technique (combined desorption andionization efficiency) is similar for different hydrocarbontypes and fairly uniform over a wide molecular weightrange, thus allowing quantitative analysis of the base oils.Hence, the product ions' relative abundances were usedto determine the percentage of each type of hydrocarbonin the base oil. In summary, three important parameters(MW distributions, hydrocarbon types, and their relativeconcentrations) can be obtained in a single experiment.This mass spectrometric technique therefore providesdetailed molecular-level information for base oils, whichcannot be obtained by other analytical methods.