This document describes the enhanced analysis of semi-volatile compounds using sub-ambient ELSD and HPLC. Evaporative light scattering detection (ELSD) is a powerful tool that can detect any sample that is less volatile than the mobile phase in HPLC applications, regardless of the optical properties of the compounds. ELSD offers distinct advantages over conventional UV or DAD detection, especially for gradient separations. In order to maximize the detection of non-UV absorbing semi-volatile analytes, ELSD detectors need to operate at lower temperatures. Most ELSDs today can evaporate highly aqueous eluents at ambient temperature, but for low molecular weight, low boiling point compounds, ambient temperature is still too high and sensitivity is poor. Sub-ambient ELSD is required to improve the detection of these compounds. The Agilent 385-ELSD is specifically designed to operate under these demanding conditions. It features a Peltier cooled evaporation tube that provides sub-ambient ELS detection down to 10 °C. Dry nitrogen gas is added during the evaporation step to facilitate solvent removal at sub-ambient temperatures.
Evaporative light scattering detection (ELSD) is a powerful tool for detecting samples less volatile than the mobile phase in HPLC applications. While most ELSDs operate at ambient temperature, low molecular weight compounds require sub-ambient temperatures to maximize sensitivity and minimize thermal degradation.
The Agilent 385-ELSD features a Peltier cooled evaporation tube capable of operation down to 10 °C. This document details how operating the detector below room temperature improves detection for analytes like acetanilide and polyethylene glycol (PEG 106), demonstrating significant sensitivity gains compared to ambient conditions.
The 385-ELSD contains a Peltier cooled evaporation tube that provides sub-ambient ELS detection down to 10 °C.
PEG 106 shows a 40-fold increase in sensitivity when the temperature is reduced from 30 °C to 20 °C.
The conditions for the acetanilide analysis use a flow rate of 1.0 mL/min and an injection volume of 20 uL.