The on-line combination of liquid chromatography (LC) and mass spectrometry (MS) is a powerful and routinely applicable analytical tool used for many applications. In general, its applications are directed towards the separation, identification and quantification of unknown and known compounds, and the elucidation of the structure and chemical properties of different molecules. It is very useful for the analysis of small molecules and provides higher sensitivity and selectivity in the trace analysis of multicomponent substances.

The Main Components of LC-MS System

The main components of the LC-MS system are described below.

HPLC System

A HPLC system is used to separate the components of a mixture based on their physical and chemical properties.

Ion Source

This is the part of the LC/MS system where the analyte molecules are ionized. The ion source can be of various types such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), or matrix-assisted laser desorption/ionization (MALDI).

Mass Analyzer

The mass analyzer is a device that separates the ions according to their mass-to-charge ratio (m/z). Common types of mass analyzers include quadrupoles, time-of-flight (TOF), and ion trap.

Detector

The detector measures the ion signal produced by the mass analyzer and converts it into an electrical signal, which is then processed and analyzed by a computer. Common types of detectors include electron multipliers and photomultiplier tubes.

Data System

The data system controls the LC/MS system and collects, processes, and analyzes the data generated during the analysis. It includes software for instrument control, data acquisition, and data analysis.

The Role of Computer Systems in LC-MS

The LC/MS system consists of an HPLC pumping system, injector, and column coupled to a mass spectrometer through some type of evaporative ionizing interface. The LC/MS system's components are controlled by a computer system that regulates the HPLC's flow rate, solvent gradient, and remote starting of injection and gradient run. The system also manages the scanning range and lens of the mass spectrometer, and accesses and processes data from the ion detector's amplifier. All of this is done through a remote control interface or through A/D (analog-to-digital; data input) and D/A (digital-to-analog; control) microprocessor cards in the computer system module. Subsequently, the computer software processes the digital data received from the A/D card to generate a total ion chromatogram (TIC), and uses the spectral data of the mass spectrometer to determine the molecular weights of the compounds present in the peaks detected [1].