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Aerosol mass spectrometry is the application of mass spectrometry to aerosol particles. Aerosol particles are defined as suspended solid and liquid particles with size range of 0.1 nm to 1000 μm in diameter.〔 Aerosol particles are produce from natural and anthropogenic sources, through a variety of different process that include; wind-blown suspension, and combustion of fossil fuels and biomass. Analysis of aerosol particles is important because of their major impacts on the global climate change, visibility, regional air pollution and human health.〔 Aerosol particles are very complex in structure and can contain thousand of different chemical compounds within a single particle. Due to this complexity the instrumentation used to analysis these particles must have the ability to separate based on size and in real-time provide information on their chemical composition. To meet these requirements for analysis, mass spectrometry instrumentation is used and they provide high sensitivity and the ability to detect a wide molecular mass range. Aerosol mass spectrometry can be divided into two categorizes; off-line and on-line.〔〔 Off-line mass spectrometry is performed on collected particles. On-line mass spectrometry is performed on particles introduced in real time. ==History== The analysis of particles in atmosphere is a topic that can be traced back to early literature, in ancient Rome there are records of complaints of foul air. Another example of early discussion of aerosols was in London (1273) and the prohibition of coal burning, because of the particulate air pollution that it was producing. Throughout history it can be seen that there was a clear need for the ability to collect and analyzing aerosol particles. Unfortunately aerosol science and measurement wasn't really established until the second half of the 19th century. The first concept of particles in the air was hypothesized by H. Becquerel in 1847, in his condensation nuclei experiment. This hypothesis was confirmed in later experiments by Coulier in 1875. 〔 John Aitken (meteorologist) (1839-1919) took Coulier and Becquerel concept even further with experiments between 1880- 1890 that demonstrated the fundamental role of dust particles in the formation of clouds and fogs. John Aitken is considered the founder of atmospheric aerosol science and aerosol measurements techniques.〔 Aitken method for aerosol analysis consisted of particle counting and sizing, which was performed using microscopic methods. This consisted of particles being collected on plates and then being counted and sized with a microscope. Using refractive index of transparent particles, the particle could be identified. Beginning in the 1920s aerosol measurements became more common place because the negative health effects of industrial aerosols and dust were starting to be recognized by health organization. 〔 The major concern at this time was the increase in incidents of silicosis in industry and mine workers. The main methods for these measurements where based off Aitken’s simple microscopic method. It wasn't until the 1960s that aerosol measurement methods started to get more complex and involve the technological and instrumentation advancements of the time. 〔 Along with the advancement in instrumentation after the 1960s came the improvement of filters and there use for sampling aerosols. This came along with the invention and application of polycarbonate filters, also called Nuclepore filters or NPFs.〔 This development was important to the field especially to off-line methods, because to obtain a representative measurement and analysis of a sample, you must have the ability to collect, store, and transport sample without disturbing the physical and chemical state of the particles. On-line aerosol measurements methods took a little longer than off-line to be developed and perfected. It wasn't till 1973 with Davis who developed and patented of the real-time single particle mass spectrometry (RTSPMS) instrument. The setup is quite similar to today’s AMS system, with the sample being introduced through a small steel capillary into the ion source region. The sample would ionize after striking a hot rhenium filament. The resulting ions were separated in a magnetic sector and detected by an electron multiplier. The method could only ionize elements with ionization potentials below the work function of the filament (~8 eV), typically alkali and alkaline earth metal. The instrument did yield unit resolution up to a mass-to-charge ratio of 115. The RTSPMS instrument had a particle transmission/detection efficiency of 0.2-0.3%. Davis used the RTSPMS instrument to study samples from calibration aerosols, ambient laboratory air, and aerosols sources. Majority of his studies where focused on inorganic salts created in lab. In Davis analysis of ambient air, he found a significant increase in lead at the end of the day, which was concluded to be due to automobile emissions. 〔〔〔〔 This development was the first step towards, today's modern on-line instruments. The next major development in technological improvement that came out of the 1970s was in 1976 by Stoffel with the development of a magnetic sector RTSPMS technique that had a direct-inlet mass spectrometry (DIMS) also known as particle-inlet mass spectrometry (PIMS).< ref name="noble"/> The PIMS instrument was the first to have a deferentially-pumped direct inlet that consists of a stainless steel capillary, followed by a skimmer and conical collimator that focuses the sample into a particle beam that goes on to the ionization region. This type of inlet system is what modern on-line aerosol mass spectrometer instruments use today. In 1982 Sinha and Fredlander developed the particle analysis by mass spectrometry (PAMS), this method was the first to incorporate the optical detection of particles followed by laser desorption/ionization (LDI) in a RTSPMS technique. Prior to this point all RTSPMS methods used surface desorption/ionization (SDI) which consist of a heated metal that ionized the samples.< ref name="noble"/> The LDI method involves the sample being hit with a continuous wave, where the particle absorbs photons, and undergoes both desorption and ionization by the same pulse. LDI has several advantages over SDI for on-line single particle mass spectrometry, as such since its development it has been the primary ionization method for RTSPMS.< ref name="noble"/> The last major step in RTSPMS development was in 1994 by Prather. Prather developed the aerosol time-of-flight mass spectrometry (ATOFMS), this method was the first that allow for simultaneous measurement of size and composition of single airborne particle. This techniques was different then previous methods in that instead of using the unreliable method of using light scattering signal intensity to measure particle size, this method uses a two laser system that allows for aerodynamic sizing.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Aerosol mass spectrometry」の詳細全文を読む スポンサード リンク
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