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Browsing by Subject "transmissiogeometria"

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  • Hannula, Juha (2015)
    Ambient mass spectrometry includes methods where ions are produced outside of the mass spectrometry in atmospheric pressure direct from the surface of the sample without sample preparation. The first and most popular ambient ionization methods are DESI, desorption electrospray ionization and DART, direct analysis in real time. DAPPI, desorption atmospheric pressure photoionization is an ionization method where samples are desorbed with hot vapor from surface and then ionized by photoionization. The aim of this study was to develop desorption atmospheric pressure photoionization method in transmission geometry. In transmission geometry hot vapor for microchip is directed through metal or polymer meshes to mass spectrometer inlet. Liquid samples can be analyzed either by soaking the mesh to liquid sample or apply a sample droplet to the mesh. Hot vapor desorbs analytes from the mesh and analytes are ionized in a gas phase by photoionization using VUV lamp. In this method optimal positioning of the mesh and the microchip was determined. Additionally optimal microchip heating power, dopant flow rate, nebulizer gas flow rate, capillary voltage and drying gas parameters were determined. Optimized method was applied for analyzing standard samples, vitamin juice samples and milk samples. According the analysis with authentic samples, transmission mode DAPPI can be applied for analyzing liquid samples without sample preparation. According the analysis with standard samples, transmission mode DAPPI can be applied for extraction of hydrophobic analytes from water samples. Comparing to conventional DAPPI, in transmission mode DAPPI spectra, intensities of the background ions are lower resulting higher signal-to-noise ratios with transmission mode DAPPI.