Due to their high salinity and low volatility, hydroxide eluents cannot be directly injected through the MS interface, where it can cause electrical shortcuts and capillary plugging by salt crystallization. The usual solution is to dilute alkaline eluents by a post-column addition of water. However, the concentrations of the analytes, and consequently the sensitivity of the detector, are reduced as well with this method. On the contrary, electrochemical desalting, also known as suppression, is an efficient way to convert hydroxide eluents into pure water. The neutralization of KOH is obtained by a combination of water electrolysis and ion-exchange: H+ are produced by the oxidation of water and are then exchanged with K+ ions of the eluent, which is therefore neutralized without diluting or modifying the analytes. In these conditions, background noise is significantly decreased and the resulting eluent is fully compatible with a MS
interface.