Novel Atmospheric Biomolecule Ionization Technologies

Mass spectrometry has been regarded as one of the most valuable analytical instruments since any compound has its intrinsic mass value. However, mass spectrometry can only be used to measure the mass-tocharge ratio (m/z) of a charged particle. Therefore, ionization process is usually needed unless the particle to be measured has an intrinsic charge. Nevertheless, the ionization efficiency is usually significantly lower than 1%. For some molecules, ionization efficiency is practically zero such as ultra-large polysaccharide (MW>1,000,000 Da). Therefore, the development of efficient ionization has always been playing a key role in mass spectrometry. In the early time, most ionization processes were pursued inside of the vacuum chamber which contains the mass spectrometer. Nevertheless, it is inconvenient if a mass spectrometer is to be used to monitor samples at in situ or real-time basis. Thus, atmospheric ionization is preferred with the advantage of little or no complex sample preparations required. Major barriers encountered for atmospheric ionization are (1) ions can be quenched due to the collision if ionization is pursued at one atmosphere (2) low transmission efficiency for ions in interest to “safely” reach to the mass analyzer which usually is under vacuum and (3) high pumping requirement to keep the pressure inside of mass spectrometer vacuum chamber stay low enough for normal operation. During the past three decades, many of the above barriers have been overcome.