Description

An analytical method known as Mass Spectrometry (MS) is used to measure the ion mass-to-charge ratio. A mass spectrum, or a plot of intensity as a function of the mass-to-charge ratio, depicts the findings. Mass spectrometry is utilized in numerous fields and can be utilized on both straightforward samples and intricate mixtures. Plots of the ion signal as a function of the mass-to-charge ratio are known as mass spectra. A sample's elemental or isotopic signature, the masses of particles and molecules, and the chemical identity or structure of molecules and other chemical compounds can all be deduced from these spectra. A typical MS procedure involves ionizing a solid, liquid or gaseous sample by bombarding it with electrons, for example. Some of the molecules in the sample might break up into positively charged fragments as a result, or they might just become positively charged without breaking up. After that, these ions (fragments) are separated based on their mass-to-charge ratio, such as by accelerating them and exposing them to an electric or magnetic field: Deflection will be the same for ions with the same mass to charge ratio. A mechanism that can detect charged particles, like an electron multiplier, detects the ions. The spectra of the signal intensity of the ions that were detected are shown as a function of the mass-to-charge ratio. Correlating known masses (such as an entire molecule) to the identified masses or using a distinctive fragmentation pattern can be used to identify the atoms or molecules in the sample.

Negatively Charged Cathode Rays

Eugen Goldstein discovered in 1886 that rays in gas discharges at low pressure traveled in the opposite direction of negatively charged cathode rays, which travel from cathode to anode, through channels in a perforated cathode. These positively charged anode rays were referred to as "Kanalstrahlen" by Goldstein; "Canal rays" is the most common English translation of this term. Wilhelm Wien built a device in 1899 with perpendicular electric and magnetic fields that separated the positive rays based on their charge-to-mass ratio (Q/m) after discovering that strong electric or magnetic fields deflected the canal rays. Wien discovered that the discharge tube's gas type affected the charge-to-mass ratio. The mass spectrograph was developed by English scientist Thomson after Wien's work was improved by lessening the pressure to do so. By 1884, the term spectrograph had entered the international scientific vocabulary. Mass spectrographs were early spectrometry instruments that recorded a spectrum of mass values on a photographic plate and measured the mass-to-charge ratio of ions. Similar to a mass spectrograph, a mass spectroscope projects an ion beam onto a phosphor screen. In the early instruments, a mass spectroscope configuration was used when it was desired to quickly observe the effects of adjustments. A photographic plate was inserted and exposed after the instrument had been properly adjusted. Even though indirect measurements with an oscilloscope replaced direct illumination of a phosphor screen, the term mass spectroscope was still used. Due to the risk of confusion with light spectroscopy, the term mass spectroscopy is no longer used. Mass spectrometry is frequently abbreviated as MS or mass-spec. Arthur and Aston created the modern mass spectrometry methods in 1918 and 1919, respectively.

Effectiveness of Various Ionization Mechanisms

Ernest invented sector mass spectrometers, or calutrons, which were used to separate uranium isotopes during the Manhattan Project. At the Oak Ridge, Tennessee Y-12 plant, which was established during World War II, calitron mass spectrometers were utilized for the purpose of uranium enrichment. Hans and Wolfgang received half of the 1989 Nobel Prize in physics for developing the ion trap method in the 1950s and 1960s. John and Koichi shared the 2002 Nobel Prize in chemistry for their contributions to the development of Electrospray Ionization (ESI) and Soft Laser Desorption (SLD) and their use in the ionization of biological macromolecules, particularly proteins. Three parts make up a mass spectrometer: A detector, a mass analyzer and an ion source. A portion of the sample is transformed into ions by the ionizer. Depending on the sample's phase (solid, liquid or gas) and the effectiveness of various ionization mechanisms for the unknown species, there are numerous ionization techniques. Ions from the sample are removed by an extraction system, which targets them through the mass analyzer and into the detector. The mass analyzer can sort the ions by their mass-to-charge ratio because of the differences in the masses of the fragments. The detector provides information for determining the abundances of each ion present by measuring the value of an indicator quantity. A multichannel plate, for instance, provides spatial information for some detectors. The operation of a sector-type spectrometer mass analyzer is outlined in the following section: Below, we'll talk about other types of analyzers. Take a look at a small amount of sodium chloride (table salt). The sample is ionized, or transformed into electrically charged particles, into sodium and chloride ions in the ion source. Chloride atoms and ions come in two stable isotopes with masses of approximately (at a natural abundance of approximately 75%) and approximately (at a natural abundance of approximately 25%). Sodium atoms and ions have a mass of approximately, making them monoisotopic. Ions passing through electric and magnetic fields in the analyzer section of the spectrometer are subjected to forces. While moving through the electric field a charged particle's speed and direction can change, as can the magnetic field's direction. The ion's mass-to-charge ratio determines the magnitude of the trajectory deflection. According to Newton's second law of motion, F=ma, the magnetic force deflects lighter ions more than heavier ions. The detector, which keeps track of the relative abundance of each type of ion, receives the streams of sorted ions from the analyzer. The isotopic composition of the original sample's constituents and its chemical element composition (i.e., the presence of sodium and chlorine) are determined using this information.