Research Mass Spectrometry

Overview

Mass spectrometry is the single most powerful analytical tool available to the organic chemist. It is widely used for both qualitative and quantitative determinations. Qualitatively, the mass spectrometer gives data leading to the identification of organic chemicals in the form of pure substances or complex mixtures. The same data, with proper calibration, can also be used to measure the concentration of those chemicals. The technique is applicable to a wide range of substances, from gaseous materials to high-molecular-weight solids.

Description

Mass spectrometry is a process involving ionization and dissociation of molecules, and the measurement of the masses and relative abundance of the various ions formed. The record of this process is the mass spectrum which is the identification marker of each organic compound.

Uses

Data generated by a mass spectrometer are used to identify unknowns, impurities, or differences and similarities between two compounds or mixtures. It is also used to verify purity or the presence of a compound. The mass spectrometer can provide useful information to:

• manufacturing and chemical processes
• pharmaceutical, cosmetic, flavor and fragrance industry
• environmental applications
• forensic science

Examples of Analyses

Low Resolution Mass Spectrometry

is used to collect nominal mass spectra. The masses and relative intensities of the ions are used to identify the compounds.

Pyrolysis/Mass Spectrometry(PY/MS)

is used for the analysis of solid organic samples such as polymers (plastics). Samples are inserted directly into the mass spectrometer via a heated probe, which is temperature programmed from ambient to as high as 500°C. Components of the solid sample volatilize and enter the mass spectrometer at different temperatures. Data are collected continuously during the process. The spectra generated at the different temperatures enable the analyst to identify the makeup of the sample. PY/MS is used extensively in comparison studies, in particular, those between a defective and a good product.

High Resolution Mass Spectrometry

gives exact masses of the ions. These are used to determine the elemental composition of each ion. It is the method of choice for research applications and pharmaceutical studies. However, it can be used in instances where identification by low resolution is not successful.

Gas Chromatography/Mass Spectrometry(GC/MS)

is the combination of two instruments used as one analytical tool for identification and quantitation. The gas chromatograph separates a complex mixture into its individual components and delivers each one to the mass spectrometer. This analysis generates a chromatogram consisting of different peaks, one for each component of a mixture. The area of each peak is used to measure quantity.

Headspace GC/MS

is used to identify the gases released from a sample at a desired temperature. A sample is placed into a closed container and heated to a specific temperature for some amount of time. A portion of the air or headspace in the container is removed and inserted into the gas chromatograph for separation. Identification is done with the mass spectrometer.