mass-to-charge ratio

(noun)

The best way to separate ions in a mass spectrometer. This number is calculated by dividing the ions weight by its charge.

Related Terms

Examples of mass-to-charge ratio in the following topics:

  • Mass Spectrometry to Measure Mass

    • Mass spectrometry is a powerful characterization method that identifies elements, isotopes, and compounds based on mass-to-charge ratios.
    • Mass spectrometers separate compounds based on a property known as the mass-to-charge ratio: the mass of the atom divided by its charge.
    • Mass analyzers separate the ions according to their mass-to-charge ratios.
    • Depending on the applied voltage, only ions of a certain mass-to-charge ratio will pass through the analyzer.
    • They are separated according to their mass-to-charge ratios.

  • Mass Spectrometer

    • Mass spectrometers use electric or magnetic fields to identify different materials.
    • Mass spectrometers, as diagramed in , separate compounds based on a property known as the mass-to-charge ratio.
    • Based on parameters, such as how long it takes the molecule to travel a certain distance or the amount of deflection caused by the field, a mass can be calculated for the ion.
    • Since the acceleration of a charge is dependent on the mass and strength of the charge, a lighter mass-to-charge ratio will not travel as far as a high mass-to-charge ratio, allowing for comparison of the physical properties of different particles.
    • This one is for the measurement of carbon dioxide isotope ratios as in the carbon-13urea breath test.

  • Examples and Applications

    • with the relativistic mass m and its charge q.
    • Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.
    • Mass analyzers separate the ions according to their mass-to-charge ratio.
    • The deflections of the particles are dependent on the mass-to-charge ratio.
    • The mass spectrometer will segregate the particles spatially allowing a detector to measure the mass-to-charge ratio of each particle.

  • Characteristics of Mass Spectra

    • A mass spectrum will usually be presented as a vertical bar graph, in which each bar represents an ion having a specific mass-to-charge ratio (m/z) and the length of the bar indicates the relative abundance of the ion.
    • Most of the ions formed in a mass spectrometer have a single charge, so the m/z value is equivalent to mass itself.
    • The highest-mass ion in a spectrum is normally considered to be the molecular ion, and lower-mass ions are fragments from the molecular ion, assuming the sample is a single pure compound.
    • Even though these compounds are very similar in size, it is a simple matter to identify them from their individual mass spectra.
    • Both distributions are observed, but the larger ethyl cation (m/z=29) is the most abundant, possibly because its size affords greater charge dispersal.

  • Properties of Electric Charges

    • Electric charge is a fundamental physical property of matter that has many parallels to mass.
    • Electric charge, like mass and volume, is a physical property of matter.
    • Like mass, electric charge in a closed system is conserved.
    • Still, the formula describing the interactions between charges is remarkably similar to that which characterizes the interactions between masses.
    • The forces (F1 and F2) sum to produce the total force, which is calculated by Coulomb's Law and is proportional to the product of the charges q1 and q2, and inversely proportional to the square of the distance (r21) between them.

  • Mass-to-Mass Conversions

    • It is not possible to directly convert from the mass of one element to the mass of another.
    • Because there is no direct way to compare the mass of butane to the mass of oxygen, the mass of butane must be converted to moles of butane:
    • Taking coefficients from the reaction equation (13 O2 and 2 C4H10), the molar ratio of O2 to C4H10 is 13:2.
    • But by converting the butane mass to moles (0.929 moles) and using the molar ratio (13 moles oxygen : 2 moles butane), one can find the molar amount of oxygen (6.05 moles) that reacts with 54.0 grams of butane.
    • A chart detailing the steps that need to be taken to convert from the mass of substance A to the mass of substance B.

  • Mass-to-Mole Conversions

    • Mass-to-mole conversions can be facilitated by employing the molar mass as a conversion ratio.
    • The relative atomic mass is a ratio between the average mass of an element and 1/12 of the mass of an atom of carbon-12.
    • The molar mass value can be used as a conversion factor to facilitate mass-to-mole and mole-to-mass conversions.
    • The compound's molar mass is necessary when converting from grams to moles.
    • After the molar mass is determined, dimensional analysis can be used to convert from grams to moles.

  • Overview of Atomic Structure

    • Although similar in mass, protons are positively charged, while neutrons have no charge.
    • Therefore, the number of neutrons in an atom contributes significantly to its mass, but not to its charge.
    • Therefore, they do not contribute much to an element's overall atomic mass.
    • Electrons contribute greatly to the atom's charge, as each electron has a negative charge equal to the positive charge of a proton.
    • Compare the behavior of electrons to that of other charged particles to discover properties of electrons such as charge and mass.

  • Fusion Reactors

    • Fusion between the nuclei is opposed by the repulsive positive electrical charge common to all nuclei because they contain protons.
    • The difference in mass is released as energy according to Albert Einstein's mass-energy equivalence formula, E = mc2.
    • The temperatures required to provide the nuclei with enough energy to overcome their repulsion is a function of the total charge.
    • The large mass ratio of the hydrogen isotopes makes their separation easy compared to the difficult uranium enrichment process.
    • This is because the rest of mass of helium and a neutron combined is less than the rest mass of deuterium and tritium combined, providing energy according to E=mc2.

  • Problems

    • Show that if charge is not accelerating, the electric field vector points to the current (not the retarded) position of the charge.
    • A particle of mass $m$, charge ${q}$, moves in a plane perpendicular to a uniform, static, magnetic field $B $.
    • A particle of mass $m$ and charge $q$ moves in a circle due to a force ${\bf F} = -\hat{\bf r} \frac{q^2}{r^2}.$ You may assume that the particle always moves non-relativistically.
    • Let's assume that $q=e\text{ }$, the charge of the electron, and ${m=m_e}$, the mass of the electron.Write your answer in (d) in terms of $r_i$, $r_0$ (the classical electron radius) and $ c$.
    • Consider ionized hydrogen gas.Each electron-proton pair has a mass more or less equal to the mass of the proton ($m_p$) and a cross section to radiation equal to the Thompson cross-section ($\sigma_T$).