LOCATION OF DOUBLE BOND POSITION OF INSECT SEX PHEROMONE BY GC/MS ANALYSIS WITH CHEMICAL IONIZATION

Ozonolysis products of four lepidopteral pheromone were identified by methane CI-MS.The spectra obtained were notably simpler than those of EI-MS,the peak of molecular ion was normally close to the base peak,and the characteristic fragment ions were high in m/z,thereby the interpretation was facilitated.

Chemical Ionization Mass Spectrometry of Pertrimethylsilylated Desulphoglucosinolates

The chemical ionization mass spectra of ten different glucosinolates isolated from rape seed have been studied. More intense diagnostic ions were identified than in the electron impact mass spectra. The method is suitable for the structure analysis of mixture of glucosinolates.

Protonated acetone ion chemical ionization time-of-flight mass spectrometry for real-time measurement of atmospheric ammonia

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.

Radiofrequency field enhanced chemical ionization with vacuum ultraviolet lamp for miniature time-of-flight mass spectrometer

It is difficult to rapidly and on-line detect trace volatile organic compounds for miniature massspectrometry due to its limited sampling volume at slow pumping speed. In this paper, we developed anew radiofrequency field enhanced chemical ionization source （RF-ECI） with vacuum ultraviolet （VUV）lamp by coupling radiofrequency electric field and direct-current field together. The experiment resultsshowed that the sensitivity of benzene, toluene, hydrogen sulfide and other compounds increased by 2-3orders of magnitude under the introduction of RF-ECI comparing to traditional single photon ionization（SPI）. At the same time, the reagent ion of O2＋ realized the charge transfer reaction chemical ionization,and the RF-ECI effectively expanded the detection range of the VUV lamp based SPI. The VUV lamp hasinherent advantages in the on-site analytical instrument for its small size and low power consumption,and the VUV lamp based RF-ECI miniature time-of-flight mass spectrometer （TOFMS） has a limit-of-detection for H2S as low as 0.0571 mg/m3, and it is expected to be used widely in the field of on-site rapidanalvsis.

Chemical composition of different size ultrafine particulate matter measured by nanoparticle chemical ionization mass spectrometer

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.

Exact Mass Measurements for α-Allenic Alcohol by Atmospheric Pressure Chemical Ionization/Time-of-flight Mass Spectrometry

The atmospheric pressure chemical ionization/time of flight mass spectrometry (APCI/TOF MS) was applied to determine the mass of five α allenic alcohols via their protonated molecular ions using positive ion mode. Polyethylene glycol (PEG) was used as the internal reference. All results were obtained under the resolution of about 5000 FWHM (full width at the half maximum). Solvent effects were studied and the satisfied results were obtained in acetonitrile. Compared with the theoretical values, all absolute errors were less than 1.0 mmu. The effects of nozzle potential, push pulse potential, pull pulse potential, pull bias potential and acquisition rate on exact mass determination were also discussed. APCI/TOF MS is proven to be a very sensitive analytical technique and an alternative ionization mode in analyzing thermally labile compounds with relatively weak polarity, such as α allenic alcohol.