针对目前商用质谱仪的离子源都为封闭式且工作在真空或者低气压环境中,应用范围十分受限这一问题,提出了一种新型的可在大气环境下工作的离子源。该离子源通过电晕放电产生离子,呈线-筒结构,由内电极和外筒电极组成,电极直径分别为0.16 mm和4 mm。外筒电极上开有对称的4个槽,用于通入样品和牵引离子。实验结果表明,在大气环境下,当载气为N2,内电极电压达到-3 800 V时,内电极和外筒电极之间发生电晕放电,可以很好地电离乙酸等负电性的化学物质。质谱图显示,大气中的N2和O2可能也参与电离,生成了NO－2 (m/z:46)、 NO－3 (m/z:62)和[M+NO-H]－ (m/z:89)。结合COMSOL仿真软件,对该离子源的放电起始电压进行了理论分析,分析结果与实验结果相符。此外,该离子源接口简单,可广泛应用于敞开式质谱仪、离子迁移质谱仪(IMS)和高场非对称波形离子迁移质谱仪(FAIMS)中。

The mature ion source in a commercial mass spectrometer is sealed and works under vacuum or low atmospheric pressure environment,which limits the application of the mass spectrometer.In order to solve this problem,an ambient negative corona discharge ion source with line-cylinder electrodes is put forward in this paper.The gas discharge part in the ion source is composed of inner and outer electrodes with the diameters of 0.16 mm and 4 mm respectively.There are four slots in the outer electrode for injection of samples and traction of ions.The experiment results show that when samples are carried by N2 and the voltage on the inner electrode reaches -3 800 V,the corona discharge occurs between the inner and outer electrodes and negative substances,such as acetic acid,can be ionized under ambient conditions.The mass spectrogram suggests that N2 and O2 in the air maybe go into a reaction to generate NO－2 (m/z:46), NO－3(m/z:62) and [M+NO-H]－ (m/z:89).The corona onset voltage of the line-cylinder electrodes is analyzed with COMSOL and the theoretical result consists well with the experiment result.The simplicity of the interface of the ion source makes it available in the ambient mass spectrometer,Ion Mobility Spectrometer(IMS) and high-field Asymmetric Waveform Ion Mobility Spectrometer(FAIMS).