C_(1)~C_(3)正构醛、醇在质子转移反应飞行时间质谱中的产物离子特征分析

Characteristic Analysis of C_(1)~C_(3) n-Aldehydes and n-Alcohols in Proton Transfer Reaction Time-of-flight Mass Spectrometry

为分析C1~C3正构醛、醇化合物在质子转移反应飞行时间质谱(PTR-TOF MS)中的产物离子特征,考察了不同E/N值(E:电场强度,N:气体分子数密度)下C1~C3正构醛、醇的产物离子种类和强度的变化.结果表明,低分子量正构醇类(甲醇、乙醇和丙醇)倾向于形成质子化聚合物[nMH]+及其失水离子[nMH−H2O]+,且随着E/N值升高,醇类会产生较多裂解碎片和多聚体离子.低分子量正构醛(甲醛、乙醛和丙醛)主要产生质子化产物[MH]+和一水合质子化产物[M·H_(3)O]+,高E/N值(>125 Td)会抑制甲醛质子化,也会抑制其加合产物的生成.乙醛倾向于形成水加合物,且随着E/N值增高,质子化乙醛与一水合质子化乙醛的变化趋势相反.另外,丙醛在较高的E/N值下会产生一系列聚合物,如[MH·C_(2)H_(5)]+和[2MH]+.通过分析C1~C3正构醛、醇的质子转移反应特征及产物离子形成过程,获得了C1~C3正构醛、醇的特征离子和对应的最佳E/N设置值,为低分子量醛、醇的定性分析提供了重要依据.

Proton transfer reaction time-of-flight mass spectrometer(PTR-TOF-MS)is a kind of soft chemical ionization mass spectrometry instrument,which can realize real-time online detection of trace volatile organic compounds.The E/N value(E:electric field intensity,N:gas molecule number density)is an important parameter in the proton transfer reaction,which will affect the type and content of product ions.Herein,the effects of different E/N values on the types and relative strengths of C1-C3 n-aldehydes and n-alcohol product ions were systematically investigated,and the proton transfer reaction characteristics of C1-C3 n-aldehydes and n-alcohols as well as the formation pathways of fragment ions were studied.The results show that low mo⁃lecular weight n-alcohols(methanol,ethanol and propanol)tend to form protonated polymers[nMH]+and their dehydrated ions[nMH−H2O]+,and as the E/N value increases,n-alcohols will produce more fragments and polymer ions.Low molecular weight n-aldehydes(formaldehyde,acetaldehyde and propanal)mainly pro⁃duce protonated products[MH]+and monohydrate protonated products[M·H_(3)O]+.High E/N value(>125 Td)will inhibit the protonation of formaldehyde and the formation of its adducts.Acetaldehyde is more inclined to form water adducts,and the change trend of[CH3CHOH]+and[CH3CHOH·H_(2)O]+is opposite with the in⁃crease of E/N value.In addition,propanal will produce a series of polymers([C_(2)H_(5)CHOH·C_(2)H_(5)]+,[C_(2)H_(5)CHOH·C_(2)H_(5)CHO]+)at higher E/N values.In this paper,the best analytical E/N values and characteris⁃tic fragment ions of C1-C3 n-aldehydes and n-alcohols were obtained,which is expected to provide an impor⁃tant basis for the qualitative and quantitative analysis of low molecular weight aldehydes and alcohols.