> See also: > - [[Determining Molecular Structures]] > - [[Applications of Mass Spectrometry]] # Mass Spectrometry **Mass spectrometry** is a technique used to measure the mass and abundance of [[Ionization|ions]] (charged particles) in a sample. > [!tip] Key Points > - Relies on the *relative abundance* of isotopes It works by ionizing the sample (that is, giving the atoms or molecules in the sample a charge), and then separating the ions based on their mass-to-charge ratio. The resulting mass spectrum can be used to identify the elements present in the sample, as well as their relative abundances. Mass spectrometry is used in a wide range of applications, including drug development, environmental analysis, and materials science. ## Overview ### The Mass Spectrometer ![[Pasted image 20230124030324.png|500]] **Part 1: Vaporization** - a **Part 2: Ionization** - a **Part 3: The Detector** - The charged fragment can now be guided into a detector through a curved tube using a magnetic field to bend the ion's path. - The extent to which the ion's path is bent before hitting the detector depends on the strength of the magnetic field that is applied to the mass-to-charge (m/z) ratio of the particle ### The Mass Spectrum A **mass spectrum** is a plot that shows the *relative abundance* (y-axis) of the fragments based on their **mass to charge** ($m/z$) value (x-axis). The **base peak** is always the *tallest* (and most abundant) peak within the spectrum. The **molecular ion** ($M^{+\bullet}$) peak has the "highest" peak in the spectrum, showing the weight of the molecule in its non-fragmented state - The M+1 peak indicates an isotope ### Fragmentation Patterns ![[Pasted image 20230124034356.png|500]] **The Nitrogen Rule:** - An odd molecular weight generally indicates an odd number of nitrogen atoms in the compound. - An even molecular weight indicates either the absence of nitrogen (verified by checking molecular weight) or an even number of nitrogen atoms. ### Degrees of Unsaturation/Hydrogen Deficiency Index (HDI) $HDI =\frac{1}{2}(2C+2+N-H-X)$