Basics of Liquid Chromatograph-Mass Spectrometry

Basics of Liquid Chromatography/Mass Spectrometry

Liquid chromatography/mass spectrometry (LC/MS) is a process that melds liquid chromatography (LC) and mass spectrometry (MS) to analyze complex mixtures. Liquid chromatograph-mass spectrometers (LC-MS) are indispensable tools for quantitative and qualitative analysis that can identify, quantify and analyze compounds with high accuracy and reliability. The level of accuracy offered by LC-MS makes them invaluable to a wide range of industries and applications, including pharmaceutical analysis, environmental monitoring, and food safety testing. Shimadzu’s LC-MS also offers unique automation features, intuitive software, and supporting accessories to ensure precision in every application.

Frequently Asked Questions

What is the basic principle of LC/MS?

Liquid chromatography/mass spectrometry (LC/MS) combines liquid chromatography (LC), which separates compounds in a sample, with mass spectrometry (MS), which identifies and quantifies these compounds based on their mass-to-charge ratios (m/z). Leveraging LC’s proficiencies in the separation of molecules with MS’ highly sensitive identification capabilities, LC-MS can be used to analyze highly complex mixtures efficiently and effectively.

How does LC/MS work step by step?

LC/MS analysis begins with preparing the sample mixture, which is then injected into the LC column. Depending on the focus of your analysis and the specific capabilities of your LC-MS, the mixture will be separated into individual compounds before being eluted (or removed) from the chromatographic column to enter the mass spectrometer and begin the MS phase. At this point, these individual components are ionized and separated in a vacuum based on their mass-to-charge ratios (m/z), allowing the intensity of each ion to be measured and recorded. The relative ion intensities against m/z are then plotted in a mass spectrum, identifying the molecular breakdown of the sample mixture with respective concentration levels – also known as qualitative analysis.

What are the components of LC-MS?

The essential components of an LC-MS system include:

Liquid chromatography system, which separates the sample compounds.
Ion source, which ionizes the sample mixture.
Mass analyzer, which measures the mass-to-charge ratios of ions.
Detector, which records the ion signals for data analysis.
What are the detectors used in LC-MS?

Responsible for detecting the separated ions, the detector is a crucial element of an LC-MS. Common mass spectrometry methods and detectors include:

Mass spectrometry methods:
Quadrupole: A device used for mass filtering, selectively allowing ions with specific masses to pass through.
Time-of-Flight (TOF): A technique for high-resolution analysis that measures the time it takes for ions to reach the detector.
Ion Trap: A technique for advanced ion analysis that traps and analyzes ions.
Detectors:
Electron Multiplier: Amplifies ion signal intensity by using secondary electron emission.
Microchannel Plate: Amplify single particles or photons by using secondary electron emission.
What are the contaminants in LC/MS?

When conducting LC/MS, contaminants can affect the results of your analysis. These can include:

Carryover from previous samples.
Impurities in the mobile phase or sample matrix.
Background noise from the instrument.

By using high-quality solvents, LC-MS vials, and regularly maintaining the instrument, you’ll be able to minimize the instances of contamination and prioritize accuracy. You’ll find additional information on avoiding contamination in LC here.

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