# how does a mass spectrometer work a level

Where $$\theta’$$ equals the angle of refraction in the air gap. Ions leave the electric field at different speeds depending on their mass/charge ratio. The substance is bombarded with a beam of electrons so the atoms or molecules it contains are turned into ions. Chapter 7. There are three main components in all spectrometers; these components can vary widely between instruments for specific applications and levels of resolution. This is a result of wavelength dependence on the refractive index of the prism material. These work by dispersing the incident radiation out spatially, creating a spectrum of wavelengths (Ingle). In a mass spectrometer, atoms are converted to positive ions; these are then deflected by electric and magnetic fields before being detected. Mass spec is used alongside many analytical techniques, and provides information of the structural formula of a molecule such as proteins. One filter can be adjusted to allow various wavelengths to pass through it by manually changing the angle of the incident radiation ($$\theta$$) angle: $2d \sqrt{\epsilon^2 – \sin^2 } = m \lambda$. A Time-of-Flight Mass Spectrometer works by accelerating an ionised sample and calculating mass per charge based on how long each ‘object’ is in flight for. Wavelength selection elements are non-dispersive materials that filter out the unwanted ranges of wavelengths from the incident light source, thereby allowing only a certain range of wavelengths to pass through. Oxford University Press. Atkins, P and de Paula, J. Even large biomolecules like proteins are identifiable by mass, which means that biologists can perform some very interesting experiments using mass spectroscopy, potentially adding a new dimension to your research. Determination of Ar and Mr An instrument called a mass spectrometer is used to calculate relative atomic mass. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. This excitation produces radiation at a wavelength or a range of wavelengths, specific to the gas. How a Mass Spectrometer Works Determination of Ar and Mr An instrument called a mass spectrometer is used to calculate relative atomic mass. Mass spectrometers always work with positive ions. Thus the relative abundance of different isotopes can be measured. It is the change in the interference pattern at the detector between the two beams that is measured. One mirror is movable and the other is stationary. To analyze all of the ions, chemists simply adjust the intensity of the magnetic field until each stream hits the detector. Have questions or comments? The condition for constructive interference (and therefore wavelength selection) on a grating surface is: This relationship shows that the wavelength selection is not based on the grating material, but on the angle of incidence (?). This type of filter is not common in modern spectrometers now that there are more precise elements available for narrowing the radiation. A high voltage is applied, causing the particles to lose an electron. Chapter 3. Legal. Stage 2: Acceleration: The ions are accelerated so that they all have the same kinetic energy. Some systems also include a beam splitter that divides the incident beam and directs each portion along a different path before being recombined and directed to the detector. The former are usually lamps or heated solid materials that emit a wide range of wavelengths that must be narrowed greatly using a wavelength selection element to isolate the wavelength of interest. A spectrometer is any instrument used to view and analyze a range (or a spectrum) of a given characteristic for a substance (e.g., a range of mass-to-charge values as in mass spectrometry) , or a … For example, UV filters (as used on cameras) work by absorbing the UV radiation (100-400nm) but allowing other wavelengths to be transmitted. Others fill an entire room. There are also non-electrode lamps used as line sources that contain a gas and a piece of metal that will emit narrow radiation at the desired wavelength. This triggers photon production within the material, with more and more photons being produced as they reflect inside the material. Harcourt Brace. Ionization of the gas occurs from radiation (usually in the radio or microwave frequencies). At a certain distance from the splitter plate, the movable mirror causes constructive interference of the radiation at the detector such that a bright spot is detected. Notice that only one of the ion streams actually passes through the mass analyzer and reaches the detection unit at the back of the device. Mass spectrometry: An analytical technique used to determine the chemical constituents, or analytes, in a chemical sample. The photons are eventually focused into a narrow beam and then directed at the sample. Incident light can be reflected off, absorbed by, or transmitted through a sample; the way the incident light changes during the interaction with the sample is characteristic of the sample. Have a Free Meeting with one of our hand picked tutors from the UK’s top universities. New York, 2006. A Fabry-Perot Interferometer allows the incident radiation to be reflected back and forth between a pair of reflective plates that are separated by an air gap (Ingle). It can also be used to measure the relative abundance of different isotopes and to predict the structure of more complex molecules. Most of the ions passing through the mass spectrometer will have a charge of 1+, so that the mass/charge ratio will be the same as the mass of the ion. MASS SPECTROMETRY The time of mass spectrometer is an instrument used for measuring the masses of atoms and molecules. Diffuse, multi-beam incident radiation passes through a lens and is directed to the plates. The other two streams hit the side of the spectrometer and are neutralized. ; Mass spectrometer: The actual device used to carry out mass spectrometry.Some mass spectrometers can sit on a tabletop. The mass of the elements individual isotopes are found as well as their abundance. Mass spec is used alongside many analytical techniques, and provides information of the structural formula of a molecule such as proteins. The heavier the particle, the lower the speed and the greater the time taken to reach the detector. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Mass spectrometry: An analytical technique used to determine the chemical constituents, or analytes, in a chemical sample. = 2? Principles of Instrumental Analysis, Fifth Edition. Here all constructively interfering radiation is focused onto a screen where it creates a dark or bright spot. It produces a mass spectrum that plots the mass-to-charge (m/z) ratio of compounds in a mixture. An interferogram is a photographic record produced by an interferometer. Other interferometers work in a similar manner, but change the angle of the mirrors rather than the position. There are numerous different kinds of mass spectrometers, all working in slightly different ways, but the basic process involves broadly the same stages. Thomas Learning, Inc. Singapore, 2001. How does a mass spectrometer work? Pavia, DL. detector where their mass/charge ratio is given and plotted as a graph against intensity. Introduction to Spectroscopy , Third Edition. Gratings are also used to disperse incident light into component wavelengths.