Improving the Evaporative Light Scattering Detector Through Experiments and Modelling

Theme: Measurement techniques

Start date: cohort 2: 2020

Supervisors: Prof. Simone Hochgreb

Agilent’s Evaporative Light Scattering Detector (ELSD) detects analyte concentration and is often used in conjunction with chromatographic techniques, wherein the chromatographic effluent is atomised to produce a spray which is dried in a drift-tube and detected via light scattering. At the moment, the details of the physics of the process are poorly understood. This gap in the knowledge shall be addressed through experiments and the development of a range of models of increasing complexity that will enlighten the mechanics of the three main stages in the detector, namely,  atomisation, transport and evaporation, and light scattering.  At the simplest level, transfer functions for the different stages will be obtained via a combination of experiment and modelling, and be joined together linking inputs (concentration, fluid properties, temperature, pressure, geometric parameters, index of refraction) to outputs (spray droplet size distribution, light scattering intensity). We will start by seeking information from the empirical correlations currently in use by the device, particularly for light scattering, to possibly derive a more robust model for future design and applications. Following the validation of a simple model, more complex models (2D and 3D) will then be implemented, including Computational Fluid Dynamics to allow for the optimisation of the device. The use of instruments for measurement of droplet size distributions, optical tweezers for measurements of liquid droplet properties and thermodynamics, and eventual elemental analysis will allow the construction of experimental databases to be used for model testing. Specific targets of the investigation will be a range of solutions (water/sugar and TCB/HDPE) with well understood behaviour, and others with diverging or non-linear behaviour, as a function of their physical and optical properties.