The absolute partial and total cross sections for electron impact ionization of carbon monoxide are reported for electron energies from 350 eV to 8000 eV.The product ions(CO^(+),C^(+),O^(+),CO^(2+),C^(2+),and O^(2+))a...The absolute partial and total cross sections for electron impact ionization of carbon monoxide are reported for electron energies from 350 eV to 8000 eV.The product ions(CO^(+),C^(+),O^(+),CO^(2+),C^(2+),and O^(2+))are measured by employing an ion imaging mass spectrometer and two ion-pair dissociation channels(C^(+)+O^(+)and C^(2+)+O^(+))are identified.The absolute cross sections for producing individual ions and their total,as well as for the ion-pair dissociation channels are obtained by normalizing the data of CO^(+)to that of Ar^(+)from CO-Ar mixture target with a fixed 1:1 ratio.The overall errors are evaluated by considering various kinds of uncertainties.A comprehensive comparison is made with the available data,which shows a good agreement with each other over the energy ranges that are overlapped.This work presents new cross-section data with electron energies above 1000 eV.展开更多
The nomenclature for compounds that are modified with isotopes is growing every day. Compounds can be modified with isotopes either individually, in a functional group or groups, or completely with all atomic centers ...The nomenclature for compounds that are modified with isotopes is growing every day. Compounds can be modified with isotopes either individually, in a functional group or groups, or completely with all atomic centers of the element. This diversity of isotope-modified compounds increases the range of researches that can be studied using them. Compounds modified with isotopes of carbon-13 or nitrogen-15 can be converted into carbon monoxide, carbon dioxide and molecular nitrogen. Currently, only the average value of carbon-13 or nitrogen-15 isotopes can be determined. However, by directly determining the atomic share of these isotopes in organic compounds modified with isotopes, information about the isotopic centers of the element can be obtained. The atomic fraction of an element is defined as a single carbon or nitrogen isotope-modified center or centers, or all centers that are isotope-modified with that element at the same time. Carbon-13 or nitrogen-15 isotopes’ atomic fraction can be determined molecularly or with fragment ions of different elemental content, or both. This makes the method self-verifying, increasing the accuracy and reliability of the results obtained. Amino acids, such as asparagine, aspartic acid, methionine, and threonine, are essential for the human body. This proposed method of isotopic analysis will increase the possibilities for scientific research using these compounds.展开更多
The skin is the largest organ of the human body,and its aging is visible to the naked eye.The aging rate of men and women is slightly different.This study compared the protein expression of skin samples on the curved ...The skin is the largest organ of the human body,and its aging is visible to the naked eye.The aging rate of men and women is slightly different.This study compared the protein expression of skin samples on the curved forearms of 11 healthy women and 9 healthy men.Quantitative proteomics analysis found that the expression of epidermal proteins in men and women of the same age group was different.Compared with female skin,in male skin,20 proteins were upregulated,and 7 proteins were downregulated.These data suggest that men and women have differences in the speed of skin aging.For the first time in this experiment,a non-invasive mass spectrometer was used to detect 27 different-related epidermal proteins between men and women.Compared with women,among the 20 epidermal proteins upregulated in men,their functions can be classified into antioxidants,epidermal lipid metabolism,signal transduction,membrane transport,and cell biological processes;the 7 downregulated proteins are involved in a variety of biological processes and inflammatory reactions.Our experiments have discovered epidermal proteins related to the differences between men and women,enriching the library of epidermal differential proteins between men and women and enriching the mechanism of skin aging between men and women from the perspective of epidermal differential proteins.展开更多
Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availabil...Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.展开更多
Most heavy crude oils underwent biodegradation and generated a significant amount of naphthenic acids. Naphthenic acids are polar compounds with the carboxylic group and are considered as a major factor affecting the ...Most heavy crude oils underwent biodegradation and generated a significant amount of naphthenic acids. Naphthenic acids are polar compounds with the carboxylic group and are considered as a major factor affecting the oil viscosity. However, the relationship between the molecular composition of naphthenic acids and oil viscosity is not well understood. This study examined a “clean” heavy oil with low contents of heteroatoms but had a high content of naphthenic acids. Naphthenic acids were fractionated by distillation and caustic extraction. The molecular composition was characterized by high-resolution Orbitrap mass spectrometry. It was found that the 2- and 3-ring naphthenic monoacids with 15–35 carbon atoms are dominant components of the acid fractions;the caustic extraction is capable of isolating naphthenic acids with less than 35 carbons, which is equivalent to the upper limit of the distillable components, but not those in the residue fraction;the total acid number of the heavy distillates is higher than that of the residue fraction;the viscosity of the distillation fraction increases exponentially with an increased boiling point of the distillates. Blending experiments indicates that there is a strong correlation between the oil viscosity and acids content, although the acid content is only a few percent of the total oil.展开更多
Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can b...Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can be synthesized either naturally or artificially. To examine the metabolism and regulate the synthesis process, compounds labeled with nitrogen or carbon isotopes need to be used. These isotopic compounds allow for more extensive research and enable studies that would otherwise be impossible. However, their use is dependent on the availability of simple, efficient methods for isotopic analysis. Currently, the determination of the atomic fraction of carbon and nitrogen isotopes is only possible through their conversion into molecular nitrogen or carbon monoxide or carbon dioxide. This leads to the loss of information about isotopic enrichment in specific centers of the molecule. This article explores a new direct approach to determining the atomic fraction of carbon and nitrogen isotopes in the isotope-modified or identical centers of these compounds. This method eliminates the transfer process and dilution due to nitrogen and carbon impurities. It is now possible to simultaneously determine the atomic fraction of nitrogen and carbon isotopes in the research substance. This method can be applied to amino acids, making it an effective tool for proposing new research methods. Several articles [1] [2] [3] have proposed similar methods for organic compounds and amino acids.展开更多
Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the cas...Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the case of the availability of reliable, express, and cheap methods, the area of their use will gradually expand. A determination of the atomic fraction of the isotopes carbon-13 and nitrogen-15 directly in glycine, leucine, isoleucine, and alanine is proposed;the modification concerns all centers or one or more identical carbon and nitrogen centers separately, as well as both isotopes at the same time. There are defined mass lines of the mass spectrum of each amino acid, through which the isotopic content of carbon and nitrogen is calculated. The processes that must be taken into account for the determination of the isotopic content are also established. Isotopic analysis of these compounds until now was carried out by transforming them into carbon oxide, dioxide, and molecular nitrogen, and determination of their content in individual centers was impossible.展开更多
市场上橄榄油掺假现象屡禁不止,传统鉴定方法存在局限性。本研究利用元素分析仪-稳定同位素比质谱仪(elemental analyzer-isotope ratio mass spectrometer,EA-IRMS)对市场上常见的7种植物油进行氢、碳稳定同位素比值检验,并对测量结果...市场上橄榄油掺假现象屡禁不止,传统鉴定方法存在局限性。本研究利用元素分析仪-稳定同位素比质谱仪(elemental analyzer-isotope ratio mass spectrometer,EA-IRMS)对市场上常见的7种植物油进行氢、碳稳定同位素比值检验,并对测量结果进行显著性差异分析,同时分析橄榄油中氢、碳稳定同位素比值的相关性。结果表明:橄榄油中δD范围为-146.78‰~-125.30‰,δ^(13)C范围为-29.72‰~-28.59‰,与其他品类植物油中氢稳定同位素比值差异显著(P<0.05),与除葵花籽油、野山茶油外的植物油中碳稳定同位素比值差异显著(P<0.05);且橄榄油中氢、碳稳定同位素比值具有较强的相关性(Pearson’s r=0.904)。计算模拟豆油、玉米油对橄榄油掺假的情况,结果表明,氢、碳稳定同位素比结合分析最低能检测出玉米油掺假10%、豆油掺假30%以上的情况。该研究可为橄榄油的掺假鉴定提供方法参考。展开更多
Using quadrupole mass spectrometer,calibration gas PFTBA was turned on in constant flow to get the signal intensity,and off to get the noise value.Different scan time and dwell time was used separately for full scan m...Using quadrupole mass spectrometer,calibration gas PFTBA was turned on in constant flow to get the signal intensity,and off to get the noise value.Different scan time and dwell time was used separately for full scan mode and SIM to find out the effect of scan rate on signal intensity and noise.展开更多
To find out the effect of scan rate on sensitivity in quadrupole mass spectrometer,DDV and 11 common hypnotic drugs were chosen for GC-MS analysis.Different scan time and dwell time was used separately for full scan m...To find out the effect of scan rate on sensitivity in quadrupole mass spectrometer,DDV and 11 common hypnotic drugs were chosen for GC-MS analysis.Different scan time and dwell time was used separately for full scan mode and SIM.Then charasteristic ions were extracted to calculate signal to noise values.展开更多
The objective of current study was to develop a validated specific stability indicating reversed-phase liquid chromatographic method for the quantitative determination of desvenlafaxine in bulk sample and pharmaceutic...The objective of current study was to develop a validated specific stability indicating reversed-phase liquid chromatographic method for the quantitative determination of desvenlafaxine in bulk sample and pharmaceutical dosage form in the presence of degradation products. Forced degradation studies were performed on bulk sample of desvenlafaxine as per ICH prescribed stress conditions using acid, base, oxidative and photolytic degradation to show the stability indicating power of the method. Significant degradation was observed under acidic stress condition and the degradation product formed was identified by LC-MS and a degradation pathway for drug has been proposed. Successful separation of drug from degradation products formed under stress conditions was achieved on a SymmetryShield column C 18 (5 mm, 250 mm 4.6 mm, i.d.) using the mobile phase consisting of a mixture of 0.2% (v/v) triethylamine in ammonium acetate (0.05 M; pH 6.5) and methanol using isocratic gradient.展开更多
The reliable operation of flexible display devices poses a significant engineering challenge regarding the metrology of high barriers against water vapor.No reliable results have been reported in the range of 10–6 g∙...The reliable operation of flexible display devices poses a significant engineering challenge regarding the metrology of high barriers against water vapor.No reliable results have been reported in the range of 10–6 g∙(m^(2)∙d)1,and there is no standard ultra-barrier for calibration.To detect trace amount of water vapor permeation through an ultra-barrier with extremely high sensitivity and a greatly reduced test period,a predictive instrument was developed by integrating permeation models into high-sensitivity mass spectrometry measurement based on dynamic accumulation,detection,and evacuation of the permeant.Detection reliability was ensured by means of calibration using a standard polymer sample.After calibration,the lower detection limit for water vapor permeation is in the range of 10–7 g∙(m^(2)∙d)1,which satisfies the ultra-barrier requirement.Predictive permeation models were developed and evaluated using experimental data so that the steady-state permeation rate can be forecasted from non-steady-state results,thus enabling effective measurement of ultra-barrier permeation within a significantly shorter test period.展开更多
Volatile components in the extracts of basil leaves (Ocimum basilicum L.) were identified by gas chromatography/mass spectrometry (GC/MS) with electron ionization (EI) mode. The major volatile components of basil unde...Volatile components in the extracts of basil leaves (Ocimum basilicum L.) were identified by gas chromatography/mass spectrometry (GC/MS) with electron ionization (EI) mode. The major volatile components of basil under investigation are α-pinene, sabinene, β-pinene, d-limonene, eucalyptol, l-linalool and estragole. Electron ionization mass spectra of these compounds have been obtained and investigated. Furthermore, the semi-empirical MNDO [Modified Neglect of Diatomic Overlap] method was used to calculate the thermochemical data for the structural properties of these compounds.展开更多
The possibility of determining atomic fractions of the isotopes of carbon directly in urea, nitrobenzene, benzophenone, benzoic acid and 2-Hydroxybenzoic acid in compounds isotopically modified by all carbon centers, ...The possibility of determining atomic fractions of the isotopes of carbon directly in urea, nitrobenzene, benzophenone, benzoic acid and 2-Hydroxybenzoic acid in compounds isotopically modified by all carbon centers, as well as by one or several identical carbon centers is considered. The mass peaks of the mass spectrum that allows determining the atomic fraction of carbon isotopes are selected. The respective formulas are proposed. Until now, isotope analysis of these compounds has been carried out by converting them to carbon monoxide or dioxide, and it has been impossible to determine the atomic fraction of carbon at individual centers.展开更多
Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reag...Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer(CIMS)in the analysis of atmospheric ammonia.In this work,a vacuum ultraviolet(VUV)Kr lamp was used to replace the radioactive source,and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia.The ionization source is designed as a separated three-zone structure,and even 90 vol.%high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv.A signal normalization processing method was designed,and with this new method,the quantitative relative standard deviation(RSD)of the instrument was decreased from 17.5%to9.1%,and the coefficient of determination was increased from 0.8340 to 0.9856.The humidity correction parameters of the instrument were calculated from different humidity,and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters.The analytical time for a single sample is only 60 sec,and the limit of detection(LOD)was 8.59 pptv(signalto-noise ratio S/N=3).The ambient measurement made in Qingdao,China,in January 2021 with this newly designed CIMS,showed that the concentration of ammonia ranged from 1 to 130 ppbv.展开更多
An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed la...An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed laser vaporization supersonic ion source are skimmed and mass separated by a Wiley-McLaren time-of-flight mass spectrometer.The ion of interest is mass selected,decelerated and dissociated by a tunable IR laser.The fragment and parent ions are reaccelerated and mass analyzed by the second time-of-flight mass spectrometer.A simple new assembly integrated with mass gate,deceleration and reacceleration ion optics was designed,which allows us to measure the infrared spectra of mass selected ions with high sensitivity and easy timing synchronization.展开更多
Objective:The study objective was to determine phenolic components for the quality control(QC)of cultivated Sarcandra glabra(Thunb.)Makino(S.glabra).Materials and Methods:A sensitive,ultra-high-performance liquid chro...Objective:The study objective was to determine phenolic components for the quality control(QC)of cultivated Sarcandra glabra(Thunb.)Makino(S.glabra).Materials and Methods:A sensitive,ultra-high-performance liquid chromatography-tandem mass spectrometric method for the simultaneous determination of 12 phenolic components has been developed.Six caffeoylquinic acids,two caffeoylshikimic acids,and four flavanonol glucosides were selected for the comprehensive analysis of distribution in different parts(root,stem,and leaf).Results:Twelve phenolic components were linear in the concentration range of 0.005–5.0μg/mL(R^(2)>0.995).The relative standard deviation of intra-day and inter-day precision across three validation runs over the entire concentration range was<5%.The recovery determined was within 5%in terms of relative error.Our results showed that the 12 phenolic compounds were mainly distributed in leaves and stems far more than those in roots.Conclusions:This study provided an ultra-high-performance liquid chromatograph with triple-quadrupole mass spectrometer quantitative method of 12 phenolic components for the QC of cultivated S.glabra.It was found that the phenolic components were significantly accumulated in the aerial parts(stems and leaves)of cultivated S.glabra.展开更多
New particle formation(NPF)is the primary source of nanoparticles and contributes a large number of concentrations of cloud condensation nuclei.In recent years,field campaigns and laboratory experiments have been cond...New particle formation(NPF)is the primary source of nanoparticles and contributes a large number of concentrations of cloud condensation nuclei.In recent years,field campaigns and laboratory experiments have been conducted to promote cognition of the mechanism for NPF and its following growth processes.The chemical composition measurement of nanoparticles could help deepen understanding of the initial step of particulate matter formation.In this work,we developed a nanoparticle chemical ionization mass spectrometer to measure nanoparticles’chemical compositions during their initial growth stage.Meanwhile,a non-radioactive ion source was designed for aerosol charging and chemical ionization.Time of flight mass spectrometer coupled with integrated aerosol size selection and collection module would guarantee the picogram level detection limit and high-resolution ability to measure the matrix of ambient samples.The performance of this equipment was overall evaluated,including the transmission efficiency and collection efficiency of custombuilt nano differential mobility analyzer,chemical ionization efficiency,and mass resolution of the mass spectrometer.The high sensitivity measurement of ammonium sulfate and methylammonium sulfate aerosols with diameters ranging from 10 to 25 nm could guarantee the application of this instrument in the ambient measurement.展开更多
Purpose We are building an MRTOF-MS(multi-reflection time-of-flight mass spectrometer)for isobaric separation for the Lanzhou Penning Trap.The potentials applied on the electrodes of our MRTOF mass analyzer operating ...Purpose We are building an MRTOF-MS(multi-reflection time-of-flight mass spectrometer)for isobaric separation for the Lanzhou Penning Trap.The potentials applied on the electrodes of our MRTOF mass analyzer operating in in-trap-lift mode have to be optimized to achieve a very high mass resolving power.Methods Our method to design and optimize an MRTOF mass analyzer has been updated to introduce constraints on the potentials,and this method now can be used to optimize the parameters of MRTOF-MS both operating in mirror-switching mode and in in-trap-lift mode.By using this method,the optimal potential parameters of the electrodes have been obtained for our MRTOF mass analyzer operating in the in-trap-lift mode.Results and conclusion With a beam size of 2.8 mm diameter and an initial average ion kinetic energy of 1500 eV,the maximal mass resolving power has been achieved to be 3.2×10^(4) with a total TOF of 7.0 ms for an ion species of ^(40)Ar^(1+).It can reach up to 5.6×10^(4) for a beam size of 0.3 mm diameter.The simulation shows that the inaccuracy of the potentials applied on the outermost mirror electrodes M1–M2 must be less than 50 ppm or preferably 20 ppm.展开更多
Phospholipids are the major building blocks of the biological membranes. Additionally, phospholipids modulate membrane trafficking and metabolites derived from their
基金Project supported by the National Key Research and Development Program of China (Grant No.2022YFA1602502)the National Natural Science Foundation of China (Grant No.12127804)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos.XDB34000000)。
文摘The absolute partial and total cross sections for electron impact ionization of carbon monoxide are reported for electron energies from 350 eV to 8000 eV.The product ions(CO^(+),C^(+),O^(+),CO^(2+),C^(2+),and O^(2+))are measured by employing an ion imaging mass spectrometer and two ion-pair dissociation channels(C^(+)+O^(+)and C^(2+)+O^(+))are identified.The absolute cross sections for producing individual ions and their total,as well as for the ion-pair dissociation channels are obtained by normalizing the data of CO^(+)to that of Ar^(+)from CO-Ar mixture target with a fixed 1:1 ratio.The overall errors are evaluated by considering various kinds of uncertainties.A comprehensive comparison is made with the available data,which shows a good agreement with each other over the energy ranges that are overlapped.This work presents new cross-section data with electron energies above 1000 eV.
文摘The nomenclature for compounds that are modified with isotopes is growing every day. Compounds can be modified with isotopes either individually, in a functional group or groups, or completely with all atomic centers of the element. This diversity of isotope-modified compounds increases the range of researches that can be studied using them. Compounds modified with isotopes of carbon-13 or nitrogen-15 can be converted into carbon monoxide, carbon dioxide and molecular nitrogen. Currently, only the average value of carbon-13 or nitrogen-15 isotopes can be determined. However, by directly determining the atomic share of these isotopes in organic compounds modified with isotopes, information about the isotopic centers of the element can be obtained. The atomic fraction of an element is defined as a single carbon or nitrogen isotope-modified center or centers, or all centers that are isotope-modified with that element at the same time. Carbon-13 or nitrogen-15 isotopes’ atomic fraction can be determined molecularly or with fragment ions of different elemental content, or both. This makes the method self-verifying, increasing the accuracy and reliability of the results obtained. Amino acids, such as asparagine, aspartic acid, methionine, and threonine, are essential for the human body. This proposed method of isotopic analysis will increase the possibilities for scientific research using these compounds.
基金the Science and Technology Action Plan for Prevention and Treatment of Major Diseases sponsored by the National Health and Family Planning Commission of the People’s Republic of China(Grant No.2017ZX-01E-002)Anhui Institute of Translational Medicine(ZHYX2020A005).
文摘The skin is the largest organ of the human body,and its aging is visible to the naked eye.The aging rate of men and women is slightly different.This study compared the protein expression of skin samples on the curved forearms of 11 healthy women and 9 healthy men.Quantitative proteomics analysis found that the expression of epidermal proteins in men and women of the same age group was different.Compared with female skin,in male skin,20 proteins were upregulated,and 7 proteins were downregulated.These data suggest that men and women have differences in the speed of skin aging.For the first time in this experiment,a non-invasive mass spectrometer was used to detect 27 different-related epidermal proteins between men and women.Compared with women,among the 20 epidermal proteins upregulated in men,their functions can be classified into antioxidants,epidermal lipid metabolism,signal transduction,membrane transport,and cell biological processes;the 7 downregulated proteins are involved in a variety of biological processes and inflammatory reactions.Our experiments have discovered epidermal proteins related to the differences between men and women,enriching the library of epidermal differential proteins between men and women and enriching the mechanism of skin aging between men and women from the perspective of epidermal differential proteins.
文摘Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.
基金supported by the National Key R&D Program of China(2018YFA0702400)Science Foundation of China University of Petroleum,Beijing(ZX20210029).
文摘Most heavy crude oils underwent biodegradation and generated a significant amount of naphthenic acids. Naphthenic acids are polar compounds with the carboxylic group and are considered as a major factor affecting the oil viscosity. However, the relationship between the molecular composition of naphthenic acids and oil viscosity is not well understood. This study examined a “clean” heavy oil with low contents of heteroatoms but had a high content of naphthenic acids. Naphthenic acids were fractionated by distillation and caustic extraction. The molecular composition was characterized by high-resolution Orbitrap mass spectrometry. It was found that the 2- and 3-ring naphthenic monoacids with 15–35 carbon atoms are dominant components of the acid fractions;the caustic extraction is capable of isolating naphthenic acids with less than 35 carbons, which is equivalent to the upper limit of the distillable components, but not those in the residue fraction;the total acid number of the heavy distillates is higher than that of the residue fraction;the viscosity of the distillation fraction increases exponentially with an increased boiling point of the distillates. Blending experiments indicates that there is a strong correlation between the oil viscosity and acids content, although the acid content is only a few percent of the total oil.
文摘Amino acids are very important compounds for the body and are involved in important functions that keep us healthy. Amino acids are essential components such as valine, proline, glutamine and glutamic acid. They can be synthesized either naturally or artificially. To examine the metabolism and regulate the synthesis process, compounds labeled with nitrogen or carbon isotopes need to be used. These isotopic compounds allow for more extensive research and enable studies that would otherwise be impossible. However, their use is dependent on the availability of simple, efficient methods for isotopic analysis. Currently, the determination of the atomic fraction of carbon and nitrogen isotopes is only possible through their conversion into molecular nitrogen or carbon monoxide or carbon dioxide. This leads to the loss of information about isotopic enrichment in specific centers of the molecule. This article explores a new direct approach to determining the atomic fraction of carbon and nitrogen isotopes in the isotope-modified or identical centers of these compounds. This method eliminates the transfer process and dilution due to nitrogen and carbon impurities. It is now possible to simultaneously determine the atomic fraction of nitrogen and carbon isotopes in the research substance. This method can be applied to amino acids, making it an effective tool for proposing new research methods. Several articles [1] [2] [3] have proposed similar methods for organic compounds and amino acids.
文摘Using compounds modified by the isotopes carbon-13 and nitrogen-15 helps conduct research in various fields of science, such as medicine, pharmacology, pharmacokinetics, metabolism, agriculture, and others. In the case of the availability of reliable, express, and cheap methods, the area of their use will gradually expand. A determination of the atomic fraction of the isotopes carbon-13 and nitrogen-15 directly in glycine, leucine, isoleucine, and alanine is proposed;the modification concerns all centers or one or more identical carbon and nitrogen centers separately, as well as both isotopes at the same time. There are defined mass lines of the mass spectrum of each amino acid, through which the isotopic content of carbon and nitrogen is calculated. The processes that must be taken into account for the determination of the isotopic content are also established. Isotopic analysis of these compounds until now was carried out by transforming them into carbon oxide, dioxide, and molecular nitrogen, and determination of their content in individual centers was impossible.
文摘市场上橄榄油掺假现象屡禁不止,传统鉴定方法存在局限性。本研究利用元素分析仪-稳定同位素比质谱仪(elemental analyzer-isotope ratio mass spectrometer,EA-IRMS)对市场上常见的7种植物油进行氢、碳稳定同位素比值检验,并对测量结果进行显著性差异分析,同时分析橄榄油中氢、碳稳定同位素比值的相关性。结果表明:橄榄油中δD范围为-146.78‰~-125.30‰,δ^(13)C范围为-29.72‰~-28.59‰,与其他品类植物油中氢稳定同位素比值差异显著(P<0.05),与除葵花籽油、野山茶油外的植物油中碳稳定同位素比值差异显著(P<0.05);且橄榄油中氢、碳稳定同位素比值具有较强的相关性(Pearson’s r=0.904)。计算模拟豆油、玉米油对橄榄油掺假的情况,结果表明,氢、碳稳定同位素比结合分析最低能检测出玉米油掺假10%、豆油掺假30%以上的情况。该研究可为橄榄油的掺假鉴定提供方法参考。
文摘Using quadrupole mass spectrometer,calibration gas PFTBA was turned on in constant flow to get the signal intensity,and off to get the noise value.Different scan time and dwell time was used separately for full scan mode and SIM to find out the effect of scan rate on signal intensity and noise.
文摘To find out the effect of scan rate on sensitivity in quadrupole mass spectrometer,DDV and 11 common hypnotic drugs were chosen for GC-MS analysis.Different scan time and dwell time was used separately for full scan mode and SIM.Then charasteristic ions were extracted to calculate signal to noise values.
文摘The objective of current study was to develop a validated specific stability indicating reversed-phase liquid chromatographic method for the quantitative determination of desvenlafaxine in bulk sample and pharmaceutical dosage form in the presence of degradation products. Forced degradation studies were performed on bulk sample of desvenlafaxine as per ICH prescribed stress conditions using acid, base, oxidative and photolytic degradation to show the stability indicating power of the method. Significant degradation was observed under acidic stress condition and the degradation product formed was identified by LC-MS and a degradation pathway for drug has been proposed. Successful separation of drug from degradation products formed under stress conditions was achieved on a SymmetryShield column C 18 (5 mm, 250 mm 4.6 mm, i.d.) using the mobile phase consisting of a mixture of 0.2% (v/v) triethylamine in ammonium acetate (0.05 M; pH 6.5) and methanol using isocratic gradient.
基金This work was supported by the National Natural Science Foundation of China(51835005 and 51911540476)the Hubei Provincial Natural Science Foundation of China(2019CFB527)+2 种基金the Hubei Provincial Natural Science Foundation of China for innovative research groups(2020CFA030)the Independent Research and Development Fund of Huazhong University of Science and Technology(HUST)(2019kfyXMBZ025)the State Key Lab of Digital Manufacturing Equipment&Technology(0225100102).
文摘The reliable operation of flexible display devices poses a significant engineering challenge regarding the metrology of high barriers against water vapor.No reliable results have been reported in the range of 10–6 g∙(m^(2)∙d)1,and there is no standard ultra-barrier for calibration.To detect trace amount of water vapor permeation through an ultra-barrier with extremely high sensitivity and a greatly reduced test period,a predictive instrument was developed by integrating permeation models into high-sensitivity mass spectrometry measurement based on dynamic accumulation,detection,and evacuation of the permeant.Detection reliability was ensured by means of calibration using a standard polymer sample.After calibration,the lower detection limit for water vapor permeation is in the range of 10–7 g∙(m^(2)∙d)1,which satisfies the ultra-barrier requirement.Predictive permeation models were developed and evaluated using experimental data so that the steady-state permeation rate can be forecasted from non-steady-state results,thus enabling effective measurement of ultra-barrier permeation within a significantly shorter test period.
文摘Volatile components in the extracts of basil leaves (Ocimum basilicum L.) were identified by gas chromatography/mass spectrometry (GC/MS) with electron ionization (EI) mode. The major volatile components of basil under investigation are α-pinene, sabinene, β-pinene, d-limonene, eucalyptol, l-linalool and estragole. Electron ionization mass spectra of these compounds have been obtained and investigated. Furthermore, the semi-empirical MNDO [Modified Neglect of Diatomic Overlap] method was used to calculate the thermochemical data for the structural properties of these compounds.
文摘The possibility of determining atomic fractions of the isotopes of carbon directly in urea, nitrobenzene, benzophenone, benzoic acid and 2-Hydroxybenzoic acid in compounds isotopically modified by all carbon centers, as well as by one or several identical carbon centers is considered. The mass peaks of the mass spectrum that allows determining the atomic fraction of carbon isotopes are selected. The respective formulas are proposed. Until now, isotope analysis of these compounds has been carried out by converting them to carbon monoxide or dioxide, and it has been impossible to determine the atomic fraction of carbon at individual centers.
基金partially supported by the National Special Fund for the Development of Major Research Equipment and Instrument(No.2020YFF01014503)NSF of China(No.21874134)Young Taishan Scholars(No.tsqn201909039)
文摘Ammonia(NH_(3))is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Currently,the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer(CIMS)in the analysis of atmospheric ammonia.In this work,a vacuum ultraviolet(VUV)Kr lamp was used to replace the radioactive source,and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia.The ionization source is designed as a separated three-zone structure,and even 90 vol.%high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv.A signal normalization processing method was designed,and with this new method,the quantitative relative standard deviation(RSD)of the instrument was decreased from 17.5%to9.1%,and the coefficient of determination was increased from 0.8340 to 0.9856.The humidity correction parameters of the instrument were calculated from different humidity,and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters.The analytical time for a single sample is only 60 sec,and the limit of detection(LOD)was 8.59 pptv(signalto-noise ratio S/N=3).The ambient measurement made in Qingdao,China,in January 2021 with this newly designed CIMS,showed that the concentration of ammonia ranged from 1 to 130 ppbv.
基金supported by the Ministry of Science and Technology of China(2013CB834603,2012YQ220113-3,and 2011YQ06010003)the National Natural Science Foundation of China(21273045 and 20933030)the Committee of Science and Technology of Shanghai(13XD1400800)
文摘An apparatus based on collinear tandem time-of-flight mass spectrometer has been designed for the measurement of infrared photodissociation spectroscopy of mass-selected ions in the gas phase.The ions from a pulsed laser vaporization supersonic ion source are skimmed and mass separated by a Wiley-McLaren time-of-flight mass spectrometer.The ion of interest is mass selected,decelerated and dissociated by a tunable IR laser.The fragment and parent ions are reaccelerated and mass analyzed by the second time-of-flight mass spectrometer.A simple new assembly integrated with mass gate,deceleration and reacceleration ion optics was designed,which allows us to measure the infrared spectra of mass selected ions with high sensitivity and easy timing synchronization.
基金funded by the Science and Technology Development Fund,Macao SAR(File no.0023/2019/AKP)Guangxi Science and Technology Department Fund(File no.AD17195002)。
文摘Objective:The study objective was to determine phenolic components for the quality control(QC)of cultivated Sarcandra glabra(Thunb.)Makino(S.glabra).Materials and Methods:A sensitive,ultra-high-performance liquid chromatography-tandem mass spectrometric method for the simultaneous determination of 12 phenolic components has been developed.Six caffeoylquinic acids,two caffeoylshikimic acids,and four flavanonol glucosides were selected for the comprehensive analysis of distribution in different parts(root,stem,and leaf).Results:Twelve phenolic components were linear in the concentration range of 0.005–5.0μg/mL(R^(2)>0.995).The relative standard deviation of intra-day and inter-day precision across three validation runs over the entire concentration range was<5%.The recovery determined was within 5%in terms of relative error.Our results showed that the 12 phenolic compounds were mainly distributed in leaves and stems far more than those in roots.Conclusions:This study provided an ultra-high-performance liquid chromatograph with triple-quadrupole mass spectrometer quantitative method of 12 phenolic components for the QC of cultivated S.glabra.It was found that the phenolic components were significantly accumulated in the aerial parts(stems and leaves)of cultivated S.glabra.
基金supported by the National Key Research and Development Program of China(No.2017YFC0209500)the National Natural Science Foundation of China(No.41822703)the Beijing National Laboratory for Molecular Sciences(No.BNLMS-CXXM-202011)
文摘New particle formation(NPF)is the primary source of nanoparticles and contributes a large number of concentrations of cloud condensation nuclei.In recent years,field campaigns and laboratory experiments have been conducted to promote cognition of the mechanism for NPF and its following growth processes.The chemical composition measurement of nanoparticles could help deepen understanding of the initial step of particulate matter formation.In this work,we developed a nanoparticle chemical ionization mass spectrometer to measure nanoparticles’chemical compositions during their initial growth stage.Meanwhile,a non-radioactive ion source was designed for aerosol charging and chemical ionization.Time of flight mass spectrometer coupled with integrated aerosol size selection and collection module would guarantee the picogram level detection limit and high-resolution ability to measure the matrix of ambient samples.The performance of this equipment was overall evaluated,including the transmission efficiency and collection efficiency of custombuilt nano differential mobility analyzer,chemical ionization efficiency,and mass resolution of the mass spectrometer.The high sensitivity measurement of ammonium sulfate and methylammonium sulfate aerosols with diameters ranging from 10 to 25 nm could guarantee the application of this instrument in the ambient measurement.
基金Supported by the National Natural Science Foundation of China(Grant Nos:11675224,11405243,11605268,11735017)the Chinese Academy of Sciences(No.113462KYSB20150026,QYZDJ-SSW-SLH041)the National Basic Research Program of China(973 Program)(No.2013CB834400).
文摘Purpose We are building an MRTOF-MS(multi-reflection time-of-flight mass spectrometer)for isobaric separation for the Lanzhou Penning Trap.The potentials applied on the electrodes of our MRTOF mass analyzer operating in in-trap-lift mode have to be optimized to achieve a very high mass resolving power.Methods Our method to design and optimize an MRTOF mass analyzer has been updated to introduce constraints on the potentials,and this method now can be used to optimize the parameters of MRTOF-MS both operating in mirror-switching mode and in in-trap-lift mode.By using this method,the optimal potential parameters of the electrodes have been obtained for our MRTOF mass analyzer operating in the in-trap-lift mode.Results and conclusion With a beam size of 2.8 mm diameter and an initial average ion kinetic energy of 1500 eV,the maximal mass resolving power has been achieved to be 3.2×10^(4) with a total TOF of 7.0 ms for an ion species of ^(40)Ar^(1+).It can reach up to 5.6×10^(4) for a beam size of 0.3 mm diameter.The simulation shows that the inaccuracy of the potentials applied on the outermost mirror electrodes M1–M2 must be less than 50 ppm or preferably 20 ppm.
文摘Phospholipids are the major building blocks of the biological membranes. Additionally, phospholipids modulate membrane trafficking and metabolites derived from their