This application note describes the combination of mass spectrometry and evaporative light scattering detection as a powerful tool for the analysis of pharmaceuticals. An Agilent 500 Ion Trap MS was coupled to an Agilent 385-ELSD Evaporative Light Scattering Detector for quantification of Haloperidol and its metabolites, Diazepam and Verapamil, and Ibuprofen and ß-cyclodextrin. Mass spectrometry is highly sensitive and widely used as an information rich detector, but it is not universal and some analytes do not ionize well using standard ion sources. This problem can be overcome by coupling to another kind of detector such as an evaporative light scattering detector, which has many advantages over refractive index and ultraviolet detectors.
This document details the combination of an Agilent 500 Ion Trap LC/MS equipped with an ESI source and an Agilent 385-ELSD Evaporative Light Scattering Detector. The system is configured using either a low dead volume T-piece for simultaneous detection or a divert valve for selected detection to analyze specific compounds.
The ELSD has operating parameters similar to LC/MS, such as the use of volatile mobile phases and flow rates in the range of 0.2-0.5 mL/min.
The optimized scan mode used for these methods is Enhanced 5000 Da/s.