Ionization of analytes into the gas phase is a critical step for accurate mass identification. Various types of ionization methods can be applied for optimal analyte identification. This session will involve a basic introduction to various ionization modes used in mass spectrometry and will discuss the advantages and disadvantages of each.
Due to its high specificity, the use of mass spectrometry in the clinical laboratory is rapidly increasing. Currently, various types of mass spectrometers are being used in the clinical laboratory for small molecule and protein identification. The main principle behind mass spectrometry involves the measurement of mass-to-charge (m/z) ratio of analyte ions which are present in the gas phase. Creating such gas phase ions is the task of the ionization method. Depending on the type of analysis, several different ionization modes can be used which offer various advantages; such as soft ionization methods for identification of molecular ions for heat-volatile samples. However, other samples may decompose upon heating and may require desorption methods in order to be analyzed. This presentation will cover some basic ionization modes which are offered by most common mass spectrometers used in the clinical laboratory such as: electron impact (EI), electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), matrix-assisted laser desorption/ionization (MALDI).
By the end of the session users should be able to:
1. Understand the principle behind ionization in the ion source
2. Explain acronyms used to describe ionization methods
3. Be able to distinguish between hard and soft ionization methods
4. Determine what type of ionization method is needed for various analyte identification