Liquid Chromatography-Mass Spectrometry (LCMS)

AMI uses a ThermoScientific Vanquish liquid chromatography system coupled to a TSQ Fortis triple quadrupole mass spectrometer.

Similar to GCMS, LCMS combines two analytical techniques: liquid chromatography and mass spectrometry. Liquid chromatography is used for low or non-volatile liquid mixtures to separate the compounds in the mixture. Samples are dissolved in a suitable solvent and pumped through a chromatography column. In reverse-phase LC, the column is packed with a nonpolar material and the solvent is polar, such as methanol or acetonitrile. Analyte molecules in solution are forced through the column by the mobile phase, where they interact with the stationary phase. Different chemicals will take longer or shorter times to reach the end of the column. In reverse-phase, hydrophobic chemicals will be retained longer. As the chemicals are separated, they are transferred to the mass spectrometer.

A triple quadrupole is also called a tandem mass spectrometer or LC/MS/MS. In the mass spectrometer, first the sample is ionized, then they flow into the first quadrupole. The quadrupoles filter ions by applying an oscillating radio frequency combined with a direct electric field, which leads to the separation of ions based on their mass-to-charge ratios (m/z). Within the triple quadrupole configuration, the first quadrupole isolates analyte molecular ions, the second quadrupole fragments select molecular ions, and the third quadrupole selectively isolates the ion fragments for measurement via a detector. The first quadrupole and third quadrupoles function as mass spectrometers, and the second quadrupole is a collision cell. Triple quadrupole instruments are especially useful for analyzing difficult matrices.

Typical methods include:

• EPA Method 537
• EPA Method 539
• ASTM D8421