is an apparatus for rapid quantitative and qualitative analysis of hydrocarbon compounds in a petroleum sample. It utilizes the principle of accelerating molecules in a circular path in an electrical field. The compounds are separated by centrifugal force, with the molecules having a greater mass (weight) being thrown to the outer periphery of the path. Quantitative measurements are accomplished by use of either a photographic plate or electronic determination of the relative proportions of each type of particle of a given mass.

All mass spectrometers consist of three basic parts: an ion source, a mass analyzer, and a detector system. The stages within the mass spectrometer are:

1. Producing ions from the sample
2. Separating ions of differing masses
3. Detecting the number of ions of each mass produced
4. Collating the data and generating the mass spectrum

The technique has several applications, including:

• identifying unknown compounds by the mass of the compound molecules or their fragments
• determining the "isotopic" composition of elements in a compound
• determining the "structure" of a compound by observing its fragmentation
• quantifying the amount of a compound in a sample using carefully designed methods (mass spectrometry is not inherently quantitative)
• studying the fundamentals of "gas phase ion chemistry" (the chemistry of ions and neutrals in vacuum)
• determining other physical, chemical, or even biological properties of compounds with a variety of other approaches

Also see chromatography, clay/silica gel analysis, ferrography, infrared analysis, particle count, spectrographic analysis.