Study Of New Ambient Ionization Source

Paper spray ionization is a novel ambient source which used paper as substrate and carrier which technique not only possesses the general characteristics of ambient ionization source,but also has the features of convenience,low-cost and high efficiency.However,the surface of paper substrate contains a plenty of free hydroxyl groups.When the compounds are analyzed with paper spray,these targets are difficult to be eluted off in a short time,due to the strong hydrogen bond and van de Waals interactions between paper substrates and analytes which lead to the deterioration in the analysis of paper spray.In order to weaken the interactions and improve the analysis sensitivity of paper spray ionization,some efforts have made as below:(1)Silica which is generally employed as stationary phase for chromatography was used as the coating material to modify the filter paper through a facile vacuum ?ltration method by using starch as the adhesive agent.Meanwhile,the impacts of different types of binder and the concentration of coating solution have been systematically studied.Then the obtained silica coated paper acted as the substrate for paper spray to analysis different pesticides in milk.Compared to the uncoated ?lter paper and grade SG81 paper,paper spray analysis sensitivity using the as-prepared paper improved the estimated lower limit of quantitation of seven pesticides in milk by a factor of 2 to 19-fold.(2)Metal oxide materials have been used in many fields for tis unique acid-base property and thermal stability.To combine the different materials with paper spray,a series of metal oxide coated paper substrates,including Al2O3,TiO2,ZrO2,and MgO coated paper,were prepared though the facile vacuum filtration approach by using starch as the adhesive agent and applied to the analysis of therapeutic drugs in DBS.It has demonstrated that: with the unique surface properties of Zr O2 particles,the prepared paper as a substrate for paper spray has demonstrated excellent performance in high sensitivity analysis of therapeutic drugs.In contrast to the uncoated paper substrate,an improvement of 14-164-fold in lower limit of quantitation(LLOQ)was obtained for the tested drugs using ZrO2 coated paper,which revealed that ZrO2 coated paper is a good candidate for paper spray in high sensitivity analysis.(3)In order to study the stability and analytical sensitivity of therapeutic drugs in dried blood spot,the effects of paper substrates and storage conditions were systematicallyinvestigated.The results demonstrated that using silica coated paper SG81 favored to get an abundant signal due to the unique elution behavior of target compounds in dried blood spots relative to that with grade ET31 and grade 1 paper substrates.By examining the effects of light illumination and air on the stability of therapeutic drug,it reveals that both have a similar impact on the degradation of the tested drugs,whereas storing the samples in a zip-foiled bag could effectively suppress the degradation of the analytes in dried blood spots.The analysis sensitivity of different drugs in blood samples was also compared under different storage conditions.An improvement of 2-15-fold analysis sensitivity was obtained for these drugs when the DBS were stored in a zip-foiled bag relative to that exposure to air.(4)A new ionization source named analyte migration electrospray ionization(AM-ESI)has been developed based on paper spray ionization,and its factors including capillary ori?ce size,the position of the loaded samples were systematically studied.The results demonstrated that this technique offers a platform for discrimination of different vegetable oil,rapid analysis of therapeutic drugs in blood,different hairs and other complex biological samples,laying a strong platform for the study of food safety and disease pathology.In summary,the present study has proposed two kinds of paper: SiO2 coated paper and ZrO2 coated paper to improve the analysis sensitivity of paper spray ionization.Also,a new ionization source named AM-ESI has also been developed.To our knowledge,this paper not only provides a new insight into the detection of poisonous pollutants in foodstuffs,therapeutic drugs in blood and other compounds in complex sample matrices,but also offers an experimental and theoretical basis for novel ambient ionization source.