Rapid Determination And Identification In Biological Samples And Food By Direct Analysis In Real-time(DART) Mass Spectrometry

Direct analysis in real-time(DART)is a new ambient ionization method and has been widely applied in the analysis of various samples including solids,liquids or gases.The DART technology needs minimal or no sample pretreatment and no chromatographic separation.Direct analysis can be carried out in seconds to finish the qualitative and quantitative analysis.It has shown a wide range of applications in many fields such as pharmacy,environmental pollution,food safety,criminal investigation,biomolecules and metabolite characterization.This research aims to use DART to establish analysis methods for food and biological samples.First,a method for rapid determination of?-hydroxybutyric acid(GHB)in beverages(water,sodas,beer)and urine was established by direct analysis real-time mass spectrometry(DART-MS).Samples were analyzed directly after the dilution with methanol:water(V:V=1:1).Instrument parameter settings were optimized to obtain the sensitive and accurate determination of GHB.At the sample introduction speed of 0.5 mm/s,high intensity of[M-H]~-ions for GHB were observed in the negative ion and SIR mode by utilization of high purity helium gas at 350?C.For different samples of water,sodas,beer and urine,the LODs(S/N=3)were in the range of 1~2?g/mL,while the LOQs(S/N=10)in the range of 3~5?g/mL.The linear correlation coefficients of the standard curves with different sample matrix were between 0.9899 and 0.9980.The recoveries were in the range of 80.8~115.2%with the relative standard deviations in the range of 1.9~12.8%.With its rapid analysis and simple pretreatment steps,the method is expected to have a strong advantage in the rapid screening analysis of large quantities of beverage and urine in criminal cases.Second,19 samples of lung cancer patients and 27 samples of benign lung disease were analyzed by DART-MS under the optimum conditions(positive ion mode,gas temperature at 350?C,helium as the ionized gas and nitrogen as the standby gas).15 malignant samples and 23 benign samples were selected as the sample group.PCA was applied with the aid of the software of SPSS 22.0 for classifying lung cancer and benign disease pleural effusion samples.The remaining4 samples of benign and malignant pleural effusion were selected as the validated group.The results showed that the classification of the validated group was consistent with that of the sample group.In addition,three signals(m/z 238,301 and322),which make the greatest contribution to the classification of benign and malignant samples were found by the loading plot of PCA in SPSS,indicating that they may be cancer markers for lung cancer.Third,six biogenic amines(histamine,spermine,octopamine,tyramine,putrescine,and cadaverine)in fish meat were analyzed by DART-MS.At the sample introduction speed of 0.5 mm/s,high intensities of[M+H]~+ions for biogenic amines were observed in the positive ion and SIR mode by utilization of high purity helium gas at 400?C.The results showed that the six biogenic amines were not found in fresh fish but were found in the blank spiked samples.Putrescine,cadaverine,histamine,and tyramine were found in the rotting fish.Due to the failure to find a suitable internal standard,quantitative analyzation of biogenic amines in fish using DART-MS has not been completed.In the future,the experiment will be improved.Finding a suitable internal standard,optimization of pretreatment methods,and improvement of instrument conditions such as using triple quadrupole mass spectrometry will be considered.