HPLC-Mass Spectrometry

The coupling between this chromatographic technique and mass spectrometry is complicated by the fact that even a low solvent flow, for example 0.1 ml/min. of water, generates a very high volume (153 cm3/min) of gas that the vacuum system must remove to allow separation of the ions in the gas phase. Liquid chromatography is typically used for compounds whose low volatility makes them unsuitable for handling by gas chromatography.

One of the equipment installed in the Service is equipped with two types of sources that use slightly different strategies to achieve the ionization of the analytes. The Electrospray source generates ionization by applying a potential difference of several KV between the capillary through which the flow of the column exits and the body of the ionization chamber. Electrospray ionization leads to the formation of species with multiple charges, and since a mass spectrometer is an instrument that measures the mass/charge ratio, this fact allows us to observe molecules of very high weight with an equipment that has a relatively small mass range. The APCI source uses heat to help the evaporation of the solvent and also generates an electrical discharge in the chamber that ionizes the gas generated by the evaporation of the solvent. In both cases, the nature of the solvent, the flow of the mobile phase and parameters such as the applied potential difference, influence the effectiveness of the ionization process and therefore the sensitivity of the analysis.

The other equipment installed in the Service is equipped with an ion mobility module that allows the introduction of a method of separating ions based on their molecular volume.