Overview

What is sample handling?

Sample handling covers all of the processes and hardware used to move a sample from its original container to the mass spectrometer's ion source.

Although the mass spectrometer measures ions, most samples begin as liquids, gases, solids, or dissolved extracts. Before analysis, the sample must therefore be transported, separated if required, and introduced into the ion source in a controlled and reproducible way.

A typical workflow is:

Sample → vial/container → autosampler or injection device → chromatography or direct introduction → tubing/capillary → interface → ion source → mass spectrometer

The exact pathway depends strongly on the analytical technique.

For LC–MS, samples are normally injected into a flowing liquid mobile phase, separated by an LC column and delivered to an atmospheric-pressure ion source such as electrospray ionisation (ESI).

For GC–MS, volatile compounds are vaporised, separated in a gas chromatograph and transported through a heated transfer line into the ion source.

For direct infusion, a syringe pump can deliver sample continuously to the ion source without chromatographic separation.

Why sample handling matters

Sample handling can have a major effect on:

• sensitivity

• reproducibility

• peak shape

• retention time

• carryover

• contamination

• ion suppression

• sample consumption

• quantitative accuracy

Many apparent "mass spectrometer problems" actually originate before the sample reaches the mass analyser.

For example, a blocked capillary can reduce signal, an autosampler can introduce carryover, a leaking LC connection can produce poor chromatography, and an incorrectly heated GC transfer line can cause compounds to condense before reaching the MS.

Key concept

A mass spectrometer can only analyse what successfully reaches the ion source.