title: Interlayer spray ionization mass spectrometry for the simple direct analysis of low amounts of sample.
abstract: Interlayer spray is proposed as a convenient ionization source for direct analysis by mass spectrometry. Two slices of non-absorbent substrate hold the liquid sample to form a sandwich structure. By applying a high voltage to the sample, spray is generated at the tip of the substrate. The sampling procedure can be operated easily in an open condition and the spray is processed in a semi-enclosed condition, which leads to a relatively stable process. An ultralow amount (<2 μL) of the liquid sample can be analyzed without dilution, which ensures that the natural concentration and properties of the target are maintained. Less influence from the substrate is achieved compared with the spray methods based on porous absorbent materials, which results in a sensitivity enhancement of large molecule samples. It is demonstrated that the interlayer spray is applicable for the analysis of various compounds, including therapeutic drugs, peptides, and proteins. Good linearity can be obtained at a concentration as low as 50 ng/mL in the quantitative analysis for imatinib. We also show the ability to identify the chemical residuals on surfaces with high sensitivity by the "wipe-spray" method, which is useful for the fast screening of illicit substances. Interlayer spray working with mass spectrometry provides a promising method for direct analysis in an ambient environment. Graphical Abstract The schematic of the interlayer spray ionization source.
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing, 100084, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing, 100084, China. tangf@mail.tsinghua.edu.cn.
authors.forename: Fei
authors.initials: F
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing, 100084, China.
authors.forename: Cheng'an
authors.initials: C
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing, 100084, China.
authors.forename: Xinming
authors.initials: X
authors.lastname: Huo
authors.affiliation: Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, Tsinghua University, Beijing, 100084, China.
authors.forename: Sichun
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing, 100084, China.
authors.forename: Xiaohao
authors.initials: X
authors.lastname: Wang
mesh_terms: D008832:Microchemistry / Q000379:methods*; D004364:Pharmaceutical Preparations / Q000032:analysis*; D011506:Proteins / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D004364:Pharmaceutical Preparations; D011506:Proteins
keywords: Interlayer spray; Ionization source; Mass spectrometry; Sandwich structure; Trace analysis