Research On Rapid Mass Spectrometry Method And Its Application In Food Safety Analysis

The frequent occurrence of food safety problems seriously endangers the quality and safety of people’s lives.How to quickly and accurately analyze the harmful components in a large number of food samples has become an urgent problem to be solved.Rapid mass spectrometry has attracted much attention in recent years due to its high throughput and good selectivity.The advantages of rapid mass spectrometry are tailored to the needs of food safety analysis.It is very meaningful to develop new rapid mass spectrometry techniques.In this paper,a systematic study of rapid mass spectrometry was conducted on the problems of illegal health food addition and the abuse of cationic dyes in aquiculture.Based on solid phase extraction,gel filtration and other sample pretreatment techniques,a fully automated on-line purification and enrichment pretreatment system was developed.A soft ionization mass spectrometry library for rapid non-targeted screening of banned additives in health food using ESI,APCI and DCBI as ionization methods was constructed.The purifying ability of induced phase separation technology for oily and high-pigmented samples was studied.Combining with isotope internal standard method and high-resolution mass spectrometry,the high-throughput and high-sensitivity quantitative analysis of prohibited additives of DART in complex food system was studied.The main contents include the following 6 sections.1.Effective removal of complex matrices from samples before direct perfusion can greatly enhance the analytical capability of mass spectrometry.The construction of a fully automatic sample pretreatment system with high-efficiency impurity removal can reduce the labor intensity and reduce the human error.On the basis of microcolumn separation and enrichment,a continuous flow pre-treatment device was developed,which had the functions of gel permeation chromatography,solid-phase extraction,purification and enrichment.The solvent conversion and compatibility between gel separation and solid phase extraction modules are achieved through valve switching.The communication between computer and programmable logic controller(PLC)can be achieved through serial interface.The PLC is used for intelligent control of the components in the processing device,and the pre-treatment device control system can be exchanged with the chromatographic workstation.By exchanging trigger signals,the developed fully automatic system greatly improves the analysis efficiency of rapid mass spectrometry analysis.Compared with literature and existing commercial online systems,it can effectively convert solvents,solve solvent incompatibility between SPE and GPE,and effectively solve the problem of multi-functional integration and collaboration.2.Cationic dyes such as thodamine B,malachite green,methylene blue and crystal violet are commonly used in the treatment of mycosis in aquatic products.However,due to their genotoxicity and carcinogenicity,cationic dyes have been clearly prohibited to be used in edible aquaculture,and illegal addition will cause serious food safety problems.In this section,we developed a rapid method for the determination of four dyes based on the direct perfusion-ESI and direct perfusion-APCI rapid mass spectrometry.The ion inhibition was obvious when Rhodamine B was mixed with the other three dyes under ESI condition,while it can be eliminated by a chemical vapor-phase assisted electrospray technology.Under the condition of APCI,the effect of Leidenfrost Phenomenon on dye molecule ionization was enhanced by an order of magnitude in the ionization efficiency and in the sensitivity of the dye molecules at the Leidenfrost point.Compared with direct perfusion mass spectrometry,the on-line sample pretreatment device effectively eliminated the matrix interference on the target compounds,and the signal response is increased by 1-2 orders of magnitude in actual sample analysis.3.Compared with on-line sample pretreatment,liquid-liquid extraction has the advantages of low cost and high efficiency.In this part,we developed a sample pretreatment technique for liquid-liquid extraction based on induced phase separation and applied it to the pretreatment of four cationic dyes.It was found that acetonitrile/water/NaCl was the best phase separation system.The extraction efficiency of the dyes increased with the increase of the volume fraction of acetonitrile and the amount of inducer.When the volume fraction of acetonitrile increased to 50%,the extraction efficiency did not increase significantly.The optimum amount of inducer was 0.2 g.The analytical method was validated in real samples of red wine and chili oil.The recoveries of the four dyes ranged from 86.8%to 98.4%with RSDs less than 6%.4.The use of internal standard is the key to the quantitative mass spectrometry analysis.In this part,we have developed an isotope internal standard quantitative DART-MS method for the quantitative analysis of four cationic dyes.The effects of carrier gas,carrier gas temperature,the distance between sample and cone hole,sample-nozzle distance,sample loading mode and mass analyzer on the ionization of four cationic dyes have been optimized.The triangular filter paper can obtain stable mass spectrometry signal,but the sensitivity is low.Both triangular filter paper and DART metal mesh sample device can load samples in large volume to improve the sensitivity of DART analysis.The combination of quadrupole mass analyzer and high resolution Orbitrap in series can further improve the detection sensitivity of the four dye molecules by one order of magnitude.Isotope internal standard method was used to quantitatively analyze the contents of four dye compounds in real samples.The recoveries were 87.2-118.5%and RSDs were less than 19%.The proposed two-step temperature desorption combined with Leighton Frost effect assisted enhanced ionization improves the detection ability of DART for strong polar compounds.The sensitivity of synthetic pigments is much higher than that of open mass spectrometry.5.Rapid and direct in-situ analysis of complex samples can be achieved by ambient mass spectrometry(AMS).The analyte is ionized into mass spectrometry under the action of external energy(laser,etc.),avoiding the entry of complex matrix and sample pretreatment.In this part,we established a DCBI-MS-based method for the rapid qualitative analysis of common illegal food additives,such as lidocaine,ropivacaine hydrochloride,benzocaine,bupivacaine hydrochloride.A rapid qualitativescreening of four prohibited additives in samples was achieved by MS1 and MS2 scanning modes.The results of in-situ analysis of the actual samples show that DCBI-MS analysis technology has a wide prospect in high-throughput rapid screening of the banned additives for health foods.6.Rapid mass spectrometry has unique advantages in rapid screening of banned additives.However,in practical work,a wide variety of prohibited additives should be dealt with.If all the rapid mass spectrometry information of prohibited additives can be aggregated into a database,the practical value will be greater.In this part,we systematically analyzed 490 analytes including 20 kinds of anti-microbial,anti-tumor,cardiovascular and respiratory drugs which are banned in health food.A mass spectrometry database for screening banned additives in health food was successfully constructed by using soft ionizations of direct perfusion-ESI,direct perfusion-APCI and DCBI-MS.The library contains information on ionization modes,behaviors and mass spectra of 490 banned additives.This library can be used to confirm the rapid screening of prohibited additives in actual sample analysis.Compared with the reported mass spectrometry libraries,it has many advantages,such as wide target,flexible analysis method and various signal acquisition methods.