Research And Applications Of A High Sensitive Olfactory Ion Source

Since the discovery of the desorption electrospray ionization(DESI)used under ambient conditions in 2004,more and more scientists have focused their attention on the development of ion sources used under ambient conditions.For example,the Direct analysis in real-time(Dart)developed by Professor Cody[1]in 2005,the dielectric barrier discharge ion source(DBDI)developed by Professor Zhang Xinrong’s[2]research group,and the Extraction electrospray ion source(EESI)developed by Professor Chen Huanwen’s[3]research group.All these ion sources can be directly detected without sample preparation and under the ambient conditions.However,structurally speaking,these ion sources all require a carrier gas system to improve the ionization efficiency of the sample.Ion sources play a key role as a part of mass spectrometry,and mass spectrometry tends to be miniaturized,so the miniaturization of ion sources is also essential.In this paper,the structure of the olfactory ion source(OIS),which is not required for any additional gas,is very simple and sensitive.It can simultaneously detect multiple gases or volatile substances.The specific study includes three parts as the follows.(1)A highly sensitive olfactory ion source(OIS)was designed and developed.The best experimental conditions is that input voltage is 50 V and the pre-vacuum is 0.9 torr.The linear range was 1 μg/mL～10 μg/mL,and the correlation coefficient R2=0.99241,and successfully applied to the direct analysis of various volatile substances used in laboratories.By summarizing the test results,there are three ionization types:[M+H]+,[M+2H]+,and[2M+H]+.And three kinds of ionization mechanisms were discussed,it was thought that[M+H]+is a series of proton transfer after N2 impact by high throughput electrons to formed N2+,finally ionize the sample.[2M+H]+is likely to form a molecular cluster of the sample,[M+2H]+is the result of a double hydrogenation reaction.(2)Using the developed olfactory ion source,a fingerprint identification map of several volatile components of toilet water was established,which provided a new method for the identification of different brands of toilet water.In the positive ion mode,fingerprint signals of m/z in the range of 50-500 were detected,and the structures of the main characteristic substances were identified by MS/MS.The results showed that the olfactory ion source can achieve ionization of samples:methyl anthranilate,mosquito repellent,triacetin,DEET and diethyl phthalate as successful identification of different types and brands of toilet water markers and fingerprints of different toilet water at room temperature.(3)The olfactory ion source was connected with the ESI ion source to establish several different liquor fingerprints.Using this ion source,the unique components of liquor such as ethanol,ethyl lactate,benzothiazole,ethyl caproate,and β-phenylethanol were detected,and fingerprints of different liquors were obtained.Compared with a single olfactory ion source,the ion source has a wider application fileds,can be used to detect liquid substances.because of its simple structure,it has more application value for the miniaturization of mass spectrometry.