Mass spectrometry is a cornerstone analytical technique used in chemistry, biology, and materials science to determine the mass and composition of molecules.

TL;DR

A mass spectrometer measures the mass and abundance of ionized molecules using magnetic and electric fields.

What a Mass Spectrometer Does

It accurately weighs ions in the gas phase, revealing the mass and concentration of every component in a sample. This makes it indispensable for characterizing complex biomolecules such as proteins and for detecting trace impurities in pharmaceuticals.

How It Works

The operation of a mass spectrometer can be broken down into four essential stages:

1. Ionization: The sample is vaporized and then ionized, typically by electron impact or electrospray, converting neutral molecules into charged particles that the instrument can manipulate.
2. Acceleration and Deflection: Ions are accelerated toward a detector and deflected by electric and magnetic fields. Because the deflection depends on the mass‑to‑charge ratio (m/z), ions of different masses follow distinct trajectories.
3. Mass Analysis: In the analyzer, ions are sorted by m/z. Common analyzer types include quadrupole, time‑of‑flight, and ion‑trap, each offering unique resolution and speed.
4. Detection: The separated ions strike a detector, generating an electrical signal that is recorded as a mass spectrum—a graph of signal intensity versus m/z.

What Information It Provides

The resulting mass spectrum displays peaks whose heights correspond to the relative abundance of each ion. The most intense peak often represents the molecular ion (the intact, unfragmented molecule), while smaller peaks indicate fragment ions that can help deduce structural information.

Key Applications

Mass spectrometry underpins a broad range of scientific and industrial applications:

• Carbon Dating: By measuring ^14C/^12C ratios, it enables precise age determination of archaeological samples.
• Pharmaceutical Analysis: Detects contaminants, confirms drug identity, and monitors metabolism in pharmacokinetic studies.
• Proteomics: Identifies proteins and post‑translational modifications by fragmenting peptides.
• Environmental Monitoring: Detects trace pollutants, toxins, and volatile organic compounds.
• Biotechnology & Neonatal Screening: Rapidly screens newborns for metabolic disorders and guides therapeutic decisions.

These capabilities make mass spectrometry an indispensable tool across chemistry, biology, medicine, and materials science.