Chapter 14 - Mass Spectrometry

What is mass spectrometry

Mass spectrometry (MS) is an analytical technique used to measure the mass-to-charge ratio (m/z) of ions. In simpler terms, it allows scientists to figure out the masses of molecules or atoms in a sample and sometimes their structure.

Easier analogy

It’s a machine that weighs tiny particles like atoms or molecules and helps figure out what they are made of.

can detect from parts to billion to parts per trillion

Mass Spectrometer (Insert Visual)

What is m/z

Mass-charge ration

Charge - can be +1,+2

If there is a low m/z - there is more deflection at the magnetic field

If there is a high m/z - there is less deflection in the magnetic field

Relative intesnity

The mass of abundance within the sample

How much of a specific type (mz) is measured

👉 Abundance = how many ions of that mass and charge reach the detector

Molecular ion

The main ion (parent ion), off which little fragments occur

Is formed when an entire molecule looses an electron and becomes positively charged

when z = 1 (charge = +1), then it is a parent molecule (because all of them have the same mass anyway - as it stems from the same sample - not fragments)

Fragment ions

Are formed when the molecular ion is broken as it is in an unstable state

when the high-energy electrons in the ionization chamber cause the bonds to break - causes the molecule to break into pieces

Base peak

The most abundant and stable fragment ion (typically a fragment ion)

Is assigned intensity of 100%

All other fragments are assigned their abundance in accordance to it

Why base peak is not always the largest fragment

Is measured in respect to abundance and stability

A smaller fragment could be more stable and be more abundant than something that is larger

Abundance - Stability

If something is of a higher stability, it is able to surpass the magnetic field and stay intact all throughout the process - more that isotope is identified - leads to higher abundance

ChatGPT Outline (Easy To Understand)

• Stable fragment → survives → many ions → tall peak → base peak

• Unstable fragment → quickly breaks → few ions → short peak

Fragmentation

Within the ionization chamber

Electrons are bombarded

Makes the molecule electron deficient (especially in covalent bonds - shared electrons - is a big problem for stability)

Insert Visual - Interpreting Mass Spectra

Identity Peaks of the graph above

Unclear