WHAT IT IS
Liquid Chromatography–Mass Spectrometry (LC-MS) is a hyphenated analytical technique that combines liquid chromatography (for separating compounds) with mass spectrometry (for identifying and measuring them). It is used to analyze many types of molecules, from small chemicals to large biomolecules, in pharmaceuticals, medicine, food, and environmental studies.
HOW IT WORKS
Separation (LC):
The sample is carried by a liquid mobile phase through a column.
Compounds interact differently with the column and come out at different times (retention times).
Ionization (MS interface):
As compounds leave the column, they enter the ion source.
Molecules are converted into charged ions, usually by ESI, APCI, or APPI.
Mass Analysis and Detection (MS):
The ions pass into a mass analyzer (e.g., quadrupole, TOF, Orbitrap, ion trap).
They are separated by their mass-to-charge (m/z) ratios.
A detector records the signals, producing spectra or chromatograms that show the molecular weight, structure, and amount of each compound.
ADVANTAGES
Wide Analyte Coverage: Suitable for polar, nonvolatile, and thermally labile compounds.
High Sensitivity and Specificity: Detects analytes at trace levels with excellent selectivity.
Structural and Quantitative Data: MS/MS fragmentation provides structural information and accurate quantitation.
Versatility: Supports diverse applications in proteomics, metabolomics, drug development, and food safety.
Compatibility with Complex Samples: Can analyze biological fluids, plant extracts, and other challenging matrices with minimal preparation.
CHALLENGES AND LIMITATIONS
Matrix Effects: Ion suppression or enhancement can affect accuracy in complex samples.
Optimization Required: Ion source and polarity conditions must be tuned for different analytes.
Instrument Cost and Complexity: LC-MS systems are expensive and require skilled operation and maintenance.
Data Complexity: Rich spectral and chromatographic data demand advanced software and expertise for interpretation.
Mobile Phase Constraints: Non-volatile buffers and additives can interfere with ionization and reduce system performance.