Mass Spectrometry CHEM HONORS

Mass Spectrometry This is an analytical technique that helps identify how much of a given substance (chemical) is present in a sample by measuring the mass to charge ratio A sample is bombarded by electrons, this causes the sample to fragment and form ions. These ions are separated by their mass to charge ratio via an electric or magnetic field and are then detected. Results are displayed in a spectrum containing the relative abundance of the detected ions. The atoms or molecules can be determined by comparing them to known masses

Mass Spectrometry

What can you learn from Mass Spec? Determine the elemental or isotopic signature of a sample The masses of particles or molecules Figure out the chemical structure of molecules

Mass Spectrum of Boron

Mass Spectrum of Boron 10B – 23 (relative abundance) 1.) Add the two relative abundances to get a total abundance [23+100 = 123] 2.) Divide the relative abundance by the total abundance and then multiply the value by 100% 3.) Multiply the both masses by their respective percent abundance 4.) Add the two values together to determine the relative atomic mass

Mass Spectrum of Zirconium

Determining Atomic Mass If there is….. 90Zr 51.5% abundance 91Zr 11.2% 92Zr 17.1% 94Zr 17.4% 96Zr 2.8% What is the atomic mass of Zr?

Mass Spectrum of Cl2 Sometimes the diatomic molecule, Cl2, does not fragment all the way Chlorine has two isotopes, 35Cl and 37Cl, and will also have three different diatomic molecules: 35Cl – 35Cl 35Cl – 37Cl 37Cl – 37Cl

Mass Spectrum of Cl2