Study On Performance Improvement And Application Of Paper Spray Mass Spectrometry

Paper spray mass spectrometry?PS-MS?is a popular research direction for ambient mass spectrometry?AMS?.Using AMS,mass spectrometry analysis of analytes can be performed under open conditions after direct sampling and ionization,simplifying the experimental process and providing a convenient and rapid mass spectrometry method for scientists.The PS-MS method combines the characteristics of the AMS source and electron spray ionization?ESI?.This method uses low-cost paper as the carrier,and the solid or liquid sample is added to a triangular paper substrate.Through the application of high pressure,the target molecules in the high voltage electric field are driven to reach the tip and then generate a charged spray for PS-MS.To date,PS-MS technology has been successfully applied in various fields.This paper focuses on the improvement and application of PS-MS.The main contents include the following seven parts.1.Overview of theoretical basis and application of paper spray mass spectrometry.2.The development of a new urea-modified paper used in PS-MS.Electrospray ionization mass spectrometry?ESI-MS?analysis in the negative ion mode is adversely affected by ionization suppression,which is caused by electrical discharge and the presence of salts.Paper spray mass spectrometry?PS-MS?also suffers from the above phenomenon,as it is built on principles similar to those of ESI.Here,we report the use of a paper substrate modified by 1-[3-?trimethoxysilyl?propyl]urea to improve the sensitivity of quantitative PS-MS analysis in the negative ion mode.The results of IR,EDS and SEM showed that the surface of chromatographic paper was successfully modified with urea groups.The obtained urea-modified paper substrate can effectively bind anions and highly polar compounds in the sample solution,decreasing competitive ionization in the negative ion mode of PS-MS and significantly reducing the signal intensity of Cl^–adducts.In addition,analyte responses were significantly improved owing to the decreased electrical discharge observed for the less polar surface.The urea-modified paper effectively improved the selectivity and analytical performance of the PS-MS technology.3.The surface of the chromatographic paper was modified with trichloro?3,3,3-trifluoropropyl?silaneor1H,1H,2H,2H-perfluorooctyl trichlorosilane reagent to givepaper with a fluorous group,and a specific adsorption function.The results of infrared spectrophotometry and optical contact angle showed that the surface of the paper was successfully modified.Fluorine-fluorine interaction forces have selective specificity.Hence,when the fluorous paper is applied as a carrier for PS-MS,it can adsorb fluorine-containing substances?such as trifluoroacetic acid and perfluorooctanoic acid?and reduce their competitive inhibition for other analytes in the negative ion mode.In addition,the selective adsorption function of fluorous paper for fluorine-containingpollutants?i.e.,perfluorooctanoicacid?was preliminarily investigated.4.The rapid semi-quantitative PS-MS method for the determination of salicylic acid in urine was investigated.Salicylic acid is a metabolite of aspirin,and thus detection of salicylic acid content in urine can reflect the use of aspirin.However,the urine matrix is complex,so the use of non-modified paper substrates is difficult for directly determining salicylic acid in urine.PS-MS analysis of salicylic acid using non-modified and urea-modified paper as the carrier were contrasted,and their results showed that PS-MS analysis using urea-modified paper could effectively reduce the salt effect in urine;reduce the detection limit of the target analyte and improve the sensitivity of the PS-MS method.5.The PS-MS method was constructed using urea-modified paper and ion trap mass spectrometry for semi-quantitative analysis of ginkgolides.The main functional components of Ginkgo biloba extract are ginkgolides and ginkgo flavonoids.Due to the structural characteristics,PS-MS response of ginkgolides is vulnerable to strongly polar compounds,salt effects and electrical discharge of negative ion mode,and hence direct analysis is not easy.Experiments show that the PS-MS method established using urea-modified paper is effective compared to non-modified paper,which can reduce the matrix effect of the sample,improve the detection limit of ginkgolide and extend the application range of PS-MS.6.A PS-MS method for rapid and reliable analysis of benzalkonium chloride in compound eye drops and body surface disinfectant was developed.The sample was dropped onto a triangular filter paper,and high voltage?3.5 k V?was applied to form an electrospray.This method can give the composition of benzalkonium chloride in samples?i.e.,compound eye drops,skin disinfection sprays?,without pretreatment,solvent or chromatographic separation,and analysis time is only 10 s.The primary homologues C₁₂-BAC,C₁₄-BAC and C₁₆-BAC of benzalkonium chloride were quantitatively analyzed by PS-MS.After simple dilution,samples were quantified using the internal standard method.Ion trap mass spectrometry was scanned in SIM mode.The linear ranges of C₁₂-BAC,C₁₄-BAC and C₁₆-BAC were 1-100?g mL^-1;the linear regression coefficients were 0.998⁰.999;the detection limits?LODs?were 0.1?g mL^-1;the limit of quantification?LOQ?was<1?g mL^-1 and the method validation indicated that the method precision and accuracy were good.Compared with the HPLC-UV method,there was no significant difference between the two methods in the quantitative determination of the actual samples,but the analysis time for PS-MS was shorter?1 minute?than the HPLC-UV method.In addition,the reagent consumption of PS-MS is small,and no chromatographic separation is needed,so PS-MS is especially suitable for high-throughput analysis.7.To distinguish species,leaf spray MS was employed to directly analyze the leaves of Callicarpa L.plants.The ionization principle of leaf spray and paper spray technology is based on ESI,and leaf spray is a derivative of paper spray.A small triangular leaf sample was wetted with15?L of spray solvent,and a high DC voltage was applied to the wet leaf sample,which was positioned in front of the inlet of a mass spectrometer?⁵-10 mm?to produce electrospray ionization.The MS signals of phenylpropanoid glycosides in leaves could be sensitively detected.The content characteristics of the phenylpropanoid glycosides in five species including Callicarpae kwangtungensis Folium,Callicarpae macrophyllae Folium,Callicarpa nudiflora Folium,Callicarpae formosanae Folium,Callicarpa longissima Folium could be used to distinguish them.The mass spectra data of Callicarpa L.samples were analyzed using principal component analysis?PCA?or partial least squares-discriminant analysis?PLS-DA?.In addition,the semi-quantitative method of PS-MS was established.The rapid analysis of the active ingredients in plants can be applied to monitor the quality of these plants.