Effects of the Discharge Parameters on the Efficiency and Stability of Ambient Metastable-Induced Desorption Ionization

Ionization efficiency is an important factor for ion sources in mass spectrometry and ion mobility spectrometry.Using helium as the discharge gas,acetone as the sample,and high-field asymmetric ion mobility spectrometry（FAIMS） as the ion detection method,this work investigates in detail the effects of discharge parameters on the efficiency of ambient metastableinduced desorption ionization（AMDI） at atmospheric pressure.The results indicate that the discharge power and gas flow rate are both significantly correlated with the ionization efficiency.Specifically,an increase in the applied discharge power leads to a rapid increase in the ionization efficiency,which gradually reaches equilibrium due to ion saturation.Moreover,when the discharge voltage is fixed at 2.1 kV,a maximum efficiency can be achieved at the flow rate of 9.0 m/s.This study provides a foundation for the design and application of AMDI for on-line detection with mass spectrometry and ion mobility spectrometry.

Analyzing Brazilian Driver’s License Authenticity by Easy Ambient Sonic-Spray Ionization Mass Spectrometry

Fast and unequivocal methods of questioned document analysis are essential in forensic science. Here, a desorption/ionization technique, EASI-MS, was assessed for its ability to investigate questioned driver’s licenses (DL). Two suspects DL, displaying the same personal data in the proper fields (name and ID numbers), but with different individual photos, showing similar impressions on microscopic analysis, and authentic standards documents specimens were used as test cases. Profiles from authentic DL surface were dominated by a set of few minor ions, mainly from the plasticizers bis(2-ethylhexyl)phthalate and dibutylphthalate. The seized suspect counterfeit DL on points from personal data and photo were, however, dominated by abundant diagnostic ions of m/z 463, 507, 551, 595, 639, 683, which confirmed counterfeiting. Surfynol® and Nonoxynol-9®, which are common constituents of inkjet printing, were detected in the counterfeiting areas by high-accuracy EASI(+)-FT-ICR MS. The EASI-MS technique is shown therefore to offer an attractive tool for forensic investigation of questioned documents.

Fast Screening of Chicken Egg Lysozyme in White Wine Products by Extractive Electrospray Ionization Mass Spectrometry

Fast detection of trace lysozyme,one of the most important food allergens in white wine samples,was achieved by extractive electrospray ionization mass spectrometry without sample pretreatment in this study.The multiply-charged ions of m/z1587 were chosen for the quantitative detection of lysozyme in white wine,showing linear dynamic signal responses in a range of 5―75μg/mL with a linearity coefficient of 0.999 and an acceptable relative standard deviation（RSD） of 8.0%―15.0% for directly measuring lysozyme in the complex food samples.The limit of detection for lysozyme in white wine sample was calculated to be 5 μg/mL,which was lower than the amounts that can provoke allergic reactions（oral test with 3 mg or labial test with 1 mg/mL）.A single sample analysis was completed within 1 min.The data demonstrate that extractive electrospray ionization mass spectrometry is a useful tool for fast screening lysozyme in the complex matrix,showing promising application in the rapid detection of food allergen.

Facile detection of pesticides using atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry with multi-walled carbon nanotubes-based matrix

A novel atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry(AP-MALDIMS)method was established for the facile detection of pesticides in ambient environment.Four kinds of multi-walled carbon nanotubes(MWCNTs)-based matrix were synthesized and utilized to enhance the ionization efficiency of pesticides.Organophosphorus,anilinopyrimidine,carbamate,triazine,triazole and benzimidazole pesticides were directly desorbed and ionized from MWCNTs-based matrix in ambient environment,showing clear background and good sensitivity.In a comparison,Fe3O4-doped MWCNTs improved the intensity of pesticide ions more than the other three matrices.Moreover,MWCNTs-based matrix exhibited better performance than organic matrix.Quantitative analysis of pesticides using APMALDI-MS was validated to be adequate linearity,repeatability and sensitivity.Overall,AP-MALDI-MS combined with MWCNTs-based matrix enables the directly qualitative and quantitative analysis of pesticides in ambient environment.

Applications of ambient electric arc ionization mass spectrometry in saline samples

Salinity tolerance of ambient electric arc ionization(AEAI)was evaluated by comparing electrospray ionization for various samples at NaCl concentrations from 0 to 1000 mmol/L.AEAI-mass spectrometry(AEAI-MS)exhibited an excellent signal intensity even at NaCl concentrations of 1000 mmol/L,while the ESI-MS had no signal because high salinity has a strong inhibitory effect on analytes.The sodium adduct was verified using LiCl instead of NaCl.AEAI-MS successfully quantified saline samples with an excellent quantitative ability(R^(2)≥0.998).We also achieved some analytical samples in the buffer solution at a very high concentration and even in a saturated salt solution.Overall,AEAI-MS has protonated ions for most target analytes.In addition,the relationship between auxiliary temperature and the distance from the sample to the arc was investigated,and the results indicated that thermal desorption plays an important role in AEAI source.

Tip-assisted ambient electric arc ionization mass spectrometry for rapid detection of trace organophosphorus pesticides in strawberry

In this study,an ambient mass spectrometry(AMS)based method was developed for rapid detection of organophosphorus pesticides in strawberry.This method combines an electric arc and a microsyringe tip to realize tip-assisted ambient electric arc ionization(TAAEAI).A high-voltage electric arc can be applied to the microsyringe tip to generate an electric field,which results in corona discharge at the microsyringe tip.The juiced strawberry sample loaded on the tip could be directly ionized with TAAEAI and then analyzed by a mass spectrometer.TAAEAI-MS was successfully applied to analyze 6 organophosphorus pesticides in three strawberry samples.Malathion and profenofos were detected from the investigated strawberry samples.This method could quantitatively determine the contents of organophosphorus pesticides in strawberry with high reproducibility,high precision,and high sensitivity.Sample matrices did not interfere with the pesticide analysis.The recoveries of organophosphorus pesticides spiked in strawberry samples varied between 82.6%and 116%with relative standard deviations(RSDs)less than 9.2%.The limits of detection(LODs)varied between 0.0124µg/g and 0.0245µg/g,while the limits of quantification(LOQs)varied between 0.0413µg/g and 0.0817µg/g.The coefficients of determination(R2)of the method were determined to be>0.995.The method established here may have potential application in the detection of organophosphorus pesticides in vegetables and fruits.

Rapid detection of pesticide residues in Chinese herbal medicines by molecularly imprinted membrane electrospray ionization mass spectrometry

Chinese herbal medicines(CHMs)play an increasingly important role in the field of medicine and affects public health in the world.Although more and more strict has been employed to ensure the quality and safety of CHMs,pesticide residues in CHMs remain a serious issue and are the bottleneck for the global development of CHMs.In this work,we applied molecularly imprinted membrane electrospray mass spectrometry(MIM-ESI MS)for rapid detecting 4 classes of pesticide residues in CHMs,including organophosphorus(OPP),carbamates,pyrethroids and neonicotinoids in CHMs.Compared with our previous ambient ionization method MESI,MIM-ESI is capable of achieving a~50-fold increase in the detection limit of conventional analytical methods owing to the specificity recognition and unique enrichment of MIM.The optimal experimental conditions were determined,and the method was further validated for its sensitivity and specificity.Our data showed that MIM-ESI MS is applicable for the direct quantitation of pesticide residues in CHMs.This detection technology may help to ensure the quality of CHMs in the future.

Quantitative Analysis of Bisphenol A in Recycled Paper with a Novel Direct Inlet Probe-Atmospheric Pressure Photoionization–IonTrap-MS

A new ambient ion source was developed and its application to real samples has been demonstrated.This ion source is based on a previously build ion source using chemical ionization under atmospheric pressure and extractive electrospray ionization(DIP-APCI/EESI).To enhance the range of analytes,we added to this ion source a photoionization lamp to enable also photoionization,which allows the possibility to analyze polar(EESI),middle(APCI)and non-polar(APPI)analytes with the same source and with no or only a small change of the setup.In comparison with DIP-APCI,this ion source reaches similar analytical limits but shows better sensitivity for some aromatic and non-polar analytes.The analysis of bisphenol A from extracts of recycled paper demonstrates the use of this ion source for real samples.Quantification was possible by the use of a deuterated internal standard that was added to the papers before extraction.Here atmospheric pressure chemical ionization leads to bad results due to ion suppression,whereas atmospheric pressure photoionization shows results that fit to literature values.