GC-MS For Beginners (Gas Chromatography Mass Spectrometry)

Learn that GC-MS combines gas chromatography and mass spectrometry to separate mixture components and analyze them by mass-to-charge ratio. The technique produces three-dimensional results including gas chromatograms for qualitative/quantitative analysis and mass spectra for identifying unknown analytes.

Inject the sample into the gas chromatograph using a syringe before the column. The sample enters the mobile phase and begins interaction with the stationary phase inside the column.

Molecules separate based on their interaction with the stationary phase following the principle that like separates like. More volatile compounds exit the column faster than less volatile compounds, creating temporal separation.

As separated compounds exit the gas chromatograph column, they enter the mass spectrometer where they are ionized by electron ionization. This bombardment process converts neutral molecules into charged ions.

The ionized sample enters the quadrupole mass analyzer where four parallel rods create electrical fields. These fields cause ions to oscillate based on their mass-to-charge ratio, allowing selective detection of different ion masses.

Examine the gas chromatogram which displays detector current against retention time. The area under each peak indicates sample concentration, with larger areas representing higher concentrations.

Select individual peaks from the gas chromatogram to obtain mass spectra showing detailed mass-to-charge ratios. Use this spectral data to identify unknown substances and determine structural and chemical properties of the sample components.