Study On Rapid Analysis Of Artificial Sweeteners By Paper Spray Ionization Mass Spectrometry

Artificial sweeteners have become the preferred sweet substitute for diabetics and dieters due to their advantages of high sweetness,low calorie,and low dosage.However,according to the current research,artificial sweeteners are still dangerous.For example,long-term excessive intake of sodium saccharin can cause bladder cancer in rats,and the metabolite of cyclamate is cyclohexylamine,which has certain toxicity.The metabolism of phenylalanine produced by aspartame in the human body can cause brain damage in patients with phenylketonuria?PKU?.Owing to the limited use time of artificial sweeteners,their characteristics need further investigation and exploration.Therefore,detecting and monitoring artificial sweeteners are of great significance when artificial sweeteners cannot be avoided in food.Paper spray ionization mass spectrometry?PS-MS?and direct infusion electrospray ionization mass spectrometry?DI-ESI-MS?belong to atmospheric pressure soft ionization mass spectrometry,and they have similar ionization mechanisms,i.e.ion evaporation and charged ions residue mechanism.PS-MS,has the advantages,such as fast analysis speed,solvent-saving,simple operation etc.because its ionization process is completed in an open atmospheric environment.Despite this its poor ionization reproducibility directly affects the accuracy of the analysis method.In DI-ESI-MS mode,the sample solution is directly injected into the electrospray ion source via a chromatographic pump,then the components are ionized and analyzed by mass spectrometry.Its ionization repeatability and stability are relatively good,because its ionization process is carried out in a relatively closed environment.Based on this,the mass spectrometric responses of artificial sweeteners in DI-ESI-MS and PS-MS was compared.Deuterated saccharin sodium?SAC-d₃?was synthesized by H/D exchange method.The analysis accuracies of PS-MS by using SAC-d₃ and warfarin sodium as internal standards to saccharin sodium?SAC?,sodium cyclamate?CYC?and acesulfame-k?ACS-K?were compared.Then SAC-d₃ was used as the internal standard,and PS-MS and DI-ESI-MS method were used to detect SAC,ACS-k and CYC in the beverage,respectively.The results achieved practical significance for the detection of artificial sweeteners in food by high-throughput mass spectrometry?less than 1 minute?.The main works are as follows:1.Artificial sweeteners are frequently used in combination in food and beverage in order to eliminate the bad taste of single sweeteners.Therefore,the study on mutual inhibition of sweetener's ionization has its methodological significance for rapid mass spectrometry detection of sweeteners in food.The ionization efficiency of five artificial sweeteners(ACS-K,SAC,CYC,sucralose?SCL?,Aspartame?ASP?under different solvents?including methanol,acetonitrile,methanol-water,acetonitrile-water and methanol-acetonitrile?and under two different ionization methods were compared and studied.The results showed that the MS responses of SCL and ASP were higher when methanol-water and acetonitrile-water were used as the infusion solvents in DI-ESI-MS method.ACS-K,SAC and CYC had strong mass spectrometric response in methanol solution.In the PS-MS method,when the spray solvent was methanol,the mass spectrometry response strength of SCL,ASP,ACS-K,SAC and CYC and the detection sensitivity were both high at the same time.In view of the influence of pH on the ionization efficiency,the mass spectrometric response strength of five artificial sweeteners in DI-ESI-MS and PS-MS was investigated when methanol solutions with pH=5,6.8 and 8 were used as solvents.The results indicated that the response strength of ASP and SCL was higher in DI-ESI-MS when pH value was8.The mass spectrometric response strength of SAC,ACS-K and CYC was the highest at pH 6.8.In PS-MS,when pH value were=6.8 and 5,the mass spectrometry response strength of ASP was obviously stronger.At pH=8,SCL had the strongest mass spectral response.When pH=6.8,the mass spectrometric response strength of SAC,ACS-K and CYC was relatively strong.The results of ion efficiency comparison between blank paper?hydrophilic surface?and hydrophobic paper showed that in PS-MS,and the mass spectral response strength of five artificial sweeteners on hydrophobic paper was significantly increased?negative ionization mode?.2.The H/D exchange synthesis of SAC was studied.The catalyst,reaction temperature,reaction time etc.were optimized.The NMR and MS characterization proved that SAC-d₃ was successfully synthesized.In the PS-MS test,SAC-d₃ and warfarin sodium were used as the internal standard to investigate quantitative results on three artificial sweeteners:SAC,CYC and ACS-K.The linear correlation coefficients were as follows:SAC:0.9996,0.9992,ACS-K:0.9997,0.9991;CYC:0.9996,0.9993.The results demonstrated that the linear correlation coefficient was better with SAC-d₃ as the internal standard,which proved that the isotopic internal standard was more accurate than other internal standards in the quantitative analysis of PS-MS.3.A PS-MS rapid analysis method was developed for practical dairy and carbonated beverages with methanol and water as diluent,acetonitrile as protein precipitator and SAC-d₃ as quantitative internal standard,and was compared with DI-ESI-MS and LC-MS methods.The results showed that the LOD and LOQ of PS-MS and DI-ESI-MS were the same,0.1?g/mL and 1?g/mL,respectively.The recovery rates of DI-ESI-MS,PS-MS and LC-MS were 94%-105%,91%-105%and 95%-106%,respectively.Based on the results of LC-MS,the differences of SAC,ACS-K and CYC detection between PS-MS and DI-ESI-MS were compared.The results showed that the detection results of PS-MS and DI-ESI-MS were basically consistent with those of LC-MS.It was proved that PS-MS and DI-ESI-MS could be used as rapid screening methods for synthetic sweeteners in beverages.In comparison,PS-MS had more advantages,such as less solvent consumption and simpler equipment.