Electrospray ionization has developed mass spectrometry to the extent that high sensitivity and precision in the analysis of large, complex molecules like proteins and nucleotides can be achieved. ESI was developed in the 1980s by John Fenn, who later went on to win the Nobel Prize in Chemistry for his work. It has become an integral tool in analytical chemistry and biochemistry. MaTestLab is one of the leading testing service providers in the USA and Canada. We have a large network of testing laboratories in the USA.
Principle and Methodology of Electrospray Ionization
ESI uses a high voltage at the capillary outlet to generate a high electric field, atomizing the liquid into charged droplets. As the solvent evaporates, the droplet’s charge intensity increases, causing it to split into charged ions. This allows the analyte to enter the gas phase as a single or multiple charge, becoming a gas phase ion. Two explanations for gas phase ion generation are the ion evaporation model (IEM) proposed by Thomsona and lribarne and the charged residue model (CRM) advocated by Dole and Rllgen. Both models assume that ions are not excited by external energy and do not generate debris.
Instrumentation
ESI setup—The instrumentation consists of a capillary needle, a spray chamber, a desolvation region, an ion transfer interface, a mass analyzer, and a detector. The capillary needle introduces the sample solution, the spray chamber forms the initial aerosol, and the desolvation region evaporates the solvent. The mass analyzer measures the mass-to-charge ratios of the ions, and the detector records the ion signal for a mass spectrum.
Applications of Electrospray Ionization
Electrospray ionization (ESI) has significantly improved the sensitivity, accuracy, and complexity of analytical mixtures compared to previous mass spectrometry techniques. It is used for peptide and protein separation, identification, and tandem mass spectrometry. ESI-MS is particularly useful for oligonucleotides and structural and sequence analysis. It partially degrades a sample, allowing for molecular ion peak signal and molecular mass comparison. ESI also generates highly charged ions, reducing the mass-to-charge ratio, and allowing for molecular weight analysis. This broadens the application of mass spectrometry in the protein field.
