An ionic liquid ion source(ILIS)is a kind of high brightness ion source capable of providing high-speed positive or negative ion beams.This paper presents a miniaturized ILIS based on an array of porous metal strips.T...An ionic liquid ion source(ILIS)is a kind of high brightness ion source capable of providing high-speed positive or negative ion beams.This paper presents a miniaturized ILIS based on an array of porous metal strips.The porous emitter array,integrated with seven 10 mm long strips,is fabricated using wire electrical discharge machining(WEDM)combined with electrochemical etching.The assembled ILIS is 30 mm×30 mm×17.5 mm in size and weighs less than 25 g.A series of experiments,including anⅠ-Ⅴcharacteristic test,a retarding potential analyzer(RPA)test,and a spatial plume distribution test,have been conducted in vacuo to characterize the performance of the ILIS.Results show that the emitted current is up to about 800μA and ion transparency is as high as 94%.Besides,RPA curves reveal that the total fragmentation rate of the emitted particles accounts for 48.8%in positive mode and 59.8%in negative mode.Further,with the increase in applied acceleration voltage,the voltage loss rises while the energy efficiency decreases.It is also found that the plume perpendicular to the strips has a higher divergence than the one parallel to the strips.A numerical simulation by COMSOL reveals that the electric field distribution between the two electrodes results in such a spatial plume profile.展开更多
The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry（Nano-ESI-FT-ICR-MSn） and several peptides were chosen as examples. W...The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry（Nano-ESI-FT-ICR-MSn） and several peptides were chosen as examples. With the aid of the collision induced dissociation（CID）, FT-ICR provides not only precise mass/charge ratio, but also structure information of the selected peptides. The fragment ions were identified according to the observed molecular weights and peptide sequence was determined successfully. So Nano-ESI-FT-ICR-MSn is a useful tool for identification of the amino acid sequence of peptides with high confidence. Besides, a pathway for the dehydration of y ions without amino acids containing carboxylic acid under sustained off-resonance irradiation collision-induced dissociation（SORI-CID） condition was proposed.展开更多
The nitrogen-containing compounds in Changqing crude oil, its atmospheric residue(AR), and vacuum reside(VR) were characterized by negative and positive ion electrospray ionization(ESI) Fourier transform ion cyclotron...The nitrogen-containing compounds in Changqing crude oil, its atmospheric residue(AR), and vacuum reside(VR) were characterized by negative and positive ion electrospray ionization(ESI) Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS). The heteroatom compounds(N_1, N_2, N_1O_1, O_1, and O_2 class species) could be identified by the negative ESI analysis, while the positive mode could only detect the N_1, N_2, and N_1O_1 class species. Among them, the N_1 class species were found to be predominant in crude oil, as confirmed by either negative or positive ESI analyses,which were similar in composition to AR and VR. These compounds with higher abundance were characterized by double bond equivalent(DBE) values and carbon numbers. The composition of these compounds in crude oil and its AR as well as VR was correlated with their different boiling range, DBE values and carbon numbers. The negative ESI analysis showed that the abundant N_1 class species in crude oil and AR were centered at a DBE value of 12, and these species were likely benzocarbazoles, while the N_1 class species with the DBE value ranging from 13 to 16 having more complicated molecular structures were dominant in VR. And the positive ESI analysis gave the information of the abundant N_1 class species in crude oil, AR, and VR having the DBE values in the range of 10, 9―11, and 10―16, respectively, which were likely the compounds with the core of quinoline and benzoquinoline. The analysis confirmed that the distillation process in refinery preferentially removed the low DBE value and low molecular N-class species and brought them into the light and medium distillates, while those N-class species having a high molecular condensation in the molecules with large carbon number remained in the residual oil and could continually affect the downstream oil refining process.展开更多
The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that there are conflicts of interests between the authors and their organization. The scie...The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that there are conflicts of interests between the authors and their organization. The scientific community takes a very strong view on this matter, and the American Journal of Analytical Chemistry treats all unethical behavior seriously. This paper published in Vol. 6 No. 3 239-254, 2015 has been removed from this site. Title: Determination of Antibiotic Drug Cefdinir in Human Plasma Using Liquid Chromatography Tandem Mass Spectroscopy Author: Mohammad A. Al Bayyari, Raed S. Abu展开更多
The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that there are conflicts of interests between the authors and their organization. The scie...The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that there are conflicts of interests between the authors and their organization. The scientific community takes a very strong view on this matter, and the American Journal of Analytical Chemistry treats all unethical behavior seriously. This paper published in Vol. 5 No. 9 589-597, 2014 has been removed from this site. Title: Determination of Sibutramine and Its N-Desmethyl Metabolites in Human Plasma Using HPLC Coupled with Tandem Mass Author: Mohammad展开更多
基金supported by National Natural Science Foundation of China(No.52075334)。
文摘An ionic liquid ion source(ILIS)is a kind of high brightness ion source capable of providing high-speed positive or negative ion beams.This paper presents a miniaturized ILIS based on an array of porous metal strips.The porous emitter array,integrated with seven 10 mm long strips,is fabricated using wire electrical discharge machining(WEDM)combined with electrochemical etching.The assembled ILIS is 30 mm×30 mm×17.5 mm in size and weighs less than 25 g.A series of experiments,including anⅠ-Ⅴcharacteristic test,a retarding potential analyzer(RPA)test,and a spatial plume distribution test,have been conducted in vacuo to characterize the performance of the ILIS.Results show that the emitted current is up to about 800μA and ion transparency is as high as 94%.Besides,RPA curves reveal that the total fragmentation rate of the emitted particles accounts for 48.8%in positive mode and 59.8%in negative mode.Further,with the increase in applied acceleration voltage,the voltage loss rises while the energy efficiency decreases.It is also found that the plume perpendicular to the strips has a higher divergence than the one parallel to the strips.A numerical simulation by COMSOL reveals that the electric field distribution between the two electrodes results in such a spatial plume profile.
基金Supported by the National Natural Science Foundation of China(No.20675079)
文摘The sequence analysis of peptides was performed by nano-electrospray ionization Fourier transform ion cyclotron resonance tandem mass spectrometry（Nano-ESI-FT-ICR-MSn） and several peptides were chosen as examples. With the aid of the collision induced dissociation（CID）, FT-ICR provides not only precise mass/charge ratio, but also structure information of the selected peptides. The fragment ions were identified according to the observed molecular weights and peptide sequence was determined successfully. So Nano-ESI-FT-ICR-MSn is a useful tool for identification of the amino acid sequence of peptides with high confidence. Besides, a pathway for the dehydration of y ions without amino acids containing carboxylic acid under sustained off-resonance irradiation collision-induced dissociation（SORI-CID） condition was proposed.
基金supported by the Young Talent Fund of University Association for Science and Technoloqy in Shaanxi, China (No. 20160222)The PetroChina Innovation Foundation (No. 2016D-5007-0404)the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2017JQ2034)
文摘The nitrogen-containing compounds in Changqing crude oil, its atmospheric residue(AR), and vacuum reside(VR) were characterized by negative and positive ion electrospray ionization(ESI) Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS). The heteroatom compounds(N_1, N_2, N_1O_1, O_1, and O_2 class species) could be identified by the negative ESI analysis, while the positive mode could only detect the N_1, N_2, and N_1O_1 class species. Among them, the N_1 class species were found to be predominant in crude oil, as confirmed by either negative or positive ESI analyses,which were similar in composition to AR and VR. These compounds with higher abundance were characterized by double bond equivalent(DBE) values and carbon numbers. The composition of these compounds in crude oil and its AR as well as VR was correlated with their different boiling range, DBE values and carbon numbers. The negative ESI analysis showed that the abundant N_1 class species in crude oil and AR were centered at a DBE value of 12, and these species were likely benzocarbazoles, while the N_1 class species with the DBE value ranging from 13 to 16 having more complicated molecular structures were dominant in VR. And the positive ESI analysis gave the information of the abundant N_1 class species in crude oil, AR, and VR having the DBE values in the range of 10, 9―11, and 10―16, respectively, which were likely the compounds with the core of quinoline and benzoquinoline. The analysis confirmed that the distillation process in refinery preferentially removed the low DBE value and low molecular N-class species and brought them into the light and medium distillates, while those N-class species having a high molecular condensation in the molecules with large carbon number remained in the residual oil and could continually affect the downstream oil refining process.
文摘The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that there are conflicts of interests between the authors and their organization. The scientific community takes a very strong view on this matter, and the American Journal of Analytical Chemistry treats all unethical behavior seriously. This paper published in Vol. 6 No. 3 239-254, 2015 has been removed from this site. Title: Determination of Antibiotic Drug Cefdinir in Human Plasma Using Liquid Chromatography Tandem Mass Spectroscopy Author: Mohammad A. Al Bayyari, Raed S. Abu
文摘The following article has been retracted due to the investigation of complaints received against it. The Editorial Board found that there are conflicts of interests between the authors and their organization. The scientific community takes a very strong view on this matter, and the American Journal of Analytical Chemistry treats all unethical behavior seriously. This paper published in Vol. 5 No. 9 589-597, 2014 has been removed from this site. Title: Determination of Sibutramine and Its N-Desmethyl Metabolites in Human Plasma Using HPLC Coupled with Tandem Mass Author: Mohammad
