Ion trap performances were investigated based on digital ion trap technology with different collision gases and their pressures. Collision gases of helium ( M = 4 amu), nitrogen ( M = 28 amu) and argon ( M = 40 amu) with various pressures were adopted in ion excitation and dissociation stages for comparing the ion trap performances, including mass resolution, signal intensity, analysis ability of tandem mass spectrometric and low-mass cut off (LMCO) effect. The results indicated that when argon was used, the kinetic energy could be efficiently transferred and the LMCO effect was improved with higher ion capture and dissociation efficiencies except lower mass resolution. Higher mass resolution was realized with helium as collision gas. Furthermore, at the same gas pressure, heavier gas was beneficial to abundant fragment ions and structural information of precursor ion.
Ao Li,Man-Tong Zhao,Fa-Wen Yin,Min Zhang,Hui-Lin Liu,Da-Yong Zhou,Fereidoon Shahidi
Summary The antioxidant effects of gallic acid (GA) and its alkyl esters including methyl gallate, ethyl gallate, propyl gallate, butyl gallate (GA-C4), octyl gallate, lauryl gallate, hexadecyl gallate and octadecyl gallate in frying oil (soybean oil) and oyster during frying were investigated. Rancimat induction period (RIP) assay indicated GA and its alkyl esters effectively improved the oxidative stability of soybean oil according to the ‘polar paradox’; that is, the antioxidant effects of the polyphenols decreased in lipid system with the increasing of hydrophobicity. Results also indicated that GA and its alkyl esters all effectively retarded lipid oxidation in oyster tissue according to parameters including RIP, peroxide value and electron spin resonance assays. Moreover, the antioxidant efficiency in oyster increased with the alkyl chain length until GA-C4, and thereafter, the antioxidant effects decreased, similar to the ‘cut-off effect’. This study provides basic data for improving the oxidative stability of seafood during frying.
危险品化学品经营许可证（带存储）