Study On Protein Content Analysis Based On Mass Spectrometry

The content of protein in food is an important indicator of food detection.At present,the detection methods of food protein content mainly include Kjeldahl method and Dumas combustion method.The Kjeldahl method requires a lot of reagents,which pollutes the environment and takes a long time to detect.The Dumas combustion nitrogen determination method uses expensive platinum,tungsten and other catalysts in the reduction reaction,which is costly.In response to this situation,this article designs a fast,environmentally friendly,and accurate food protein content detection method based on mass spectrometry technology,which is of great significance for the innovation of protein content detection methods in China.Firstly,this article designs a quadrupole mass spectrometry platform for protein content detection using an electron impact ionization source(EI)and a direct current glow discharge ionization source(DC-GD).The mass spectrometry platform includes a gas extraction device,a capillary injection system,an ion source,a quadrupole mass analyzer,a detector section,and a vacuum system of the mass spectrometry platform.The characteristic of this mass spectrometry platform is that it can be combined with two ion sources,EI source and GD source.Secondly,based on the quadrupole mass spectrometry platform established for food protein content detection,this article innovatively studies a protein content mass spectrometry detection method using EI sources.(1)In order to verify the detection performance of protein content based on EI quadrupole mass spectrometry platform,through detecting nitric oxide standard gas samples with different concentrations,the measured nitric oxide ionic strength was linearly fitted with the concentration of standard gas samples,and the results obtained were in line with the linear relationship,the fitting degree was 0.94,which verified the potential of EI quadrupole mass spectrometry platform to analyze food protein content;(2)Place 1g,2g,3g,and 4g of flour into a tube furnace for full combustion,collect gas samples after combustion,and use the aforementioned EI source quadrupole mass spectrometry platform for detection.The results obtained also conform to a linear relationship,with a fitting degree of 0.99,verifying the feasibility of using the EI source for protein content mass spectrometry detection;(3)Using the above correction curve of protein content mass spectrometry intensity,we burned 4g corn meal sample and detected its gas products after combustion.The detection result of protein content was 8.34%,which was in line with expectations,and verified the accuracy of the new method of protein content mass spectrometry detection using EI source.Thirdly,based on the research of the EI source quadrupole mass spectrometry platform,the EI source was replaced with a self-designed GD source to explore the feasibility of using GD source for protein content mass spectrometry detection.Following the above detection process,experiments have shown that:(1)The linear fit of different quality flour samples is 0.96,indicating good linearity;The protein content of corn meal samples was 9.04%,basically in line with expectations.(2)Under the same conditions,the ionic strength obtained based on the GD quadrupole mass spectrometry platform is more than 10 times that of the EI source,reflecting that the GD source has higher sensitivity.In summary,this paper designs a quadrupole mass spectrometry platform with EI and GD sources for protein content detection.Its innovation lies in:(1)Developing a protein content detection method based on mass spectrometry,which has the advantages of fast,environmental protection,and accuracy;(2)We have developed a highly sensitive DC glow discharge ion source and applied it for mass spectrometry analysis of food combustion products for the first time.