# Using other reagent gases for Chemical Ionization (CI) operation - Applies to 5973A/N MSD

This document describes the use of reagent gases for chemical ionization (CI) use other than the typical Methane reagent gas. In particular this will describe the use of Isobutane and Ammonia as the reagent gas. Before attempting the use of these alternate reagent gases, the user should be familiar with CI operations of the 5973 MSD with Methane gas since the system should initially be tuned using Methane.