SEDEX LT-ELSD Model 60LT The Improved Classic SEDEX LT-ELSD™ System for Routine Applications
SEDEX LT-ELSD Model 75 The Reference Standard of High Sensitivity LT-ELS Detection
SEDEX LT-ELSD Model 85 The New performance leader
SEDEX LT-ELSD Model 754 4 Independant Channels LT-ELSD
Principle of operation
There are three steps in the detection of an eluent using an evaporative light scattering detector (ELSD):
1- Nebulization: The eluent from the column is mixed with an inert gas and passed through a narrow orifice to generate a homogeneous mist. This mist contains droplets of mobile phase and the compound of interest.
2- Evaporation of the Mobile Phase: The nebulized eluent is passed through a heated drift tube to evaporate the mobile phase.
3- Detection: The stream of solid particles enters a flow cell which includes a light source and a photomultiplier. The intensity of the light scattered by the particles is directly related to the mass of the eluted compound.
Benefits of Evaporative Light Scattering detection - ELSD
Essentially all compounds can be detected. ELSD Detection is based
on a universal property of all analytes and does not require the presence of a chromophoric group, an electroactive group, etc.
The ELSD detector response is directly related to the mass of the eluted compound. Accurate quantitative analytical data can be obtained for unidentified compounds.
Gradient mobile phases can be used to separate the sample.
Since the mobile phase is removed from the eluent before detection, a gradient can be used to optimize the separation. With ELSD detection, a broad range of mobile phase modifiers such as AcONH4, AcOH, HCOOH, TFA, NH4CO3, HFBA,
and N(C2H5)3 can be readily used to separate complex samples.
Why low temperature evaporation is critical in ELSD detection ? Conditions: Urea Sample 1µg, Stationary Phase: Asahipak, 5 µm NH2, Mobile Phase: CH3CN, H2O (85:15), Flow Rate: 1 ml/min, Detector: Sedex LT-ELSD 55 Pressure 2.2 bar, temperature as indicated
In an ELSD detector, the mobile phase is evaporated from the nebulized eluent by passing it through a heated tube. The temperature of this tube is perhaps the most critical parameter in optimizing the detection, if the temperature is too high, thermally labile compounds in the sample may decompose and will not be detected. In addition, lower ELSD operating temperature leads to the formation of larger particles, which provide a greater signal than smaller particles.
SEDEX LT-ELSD detectors can evaporate high boiling solvents at low temperatures. As an example, the Model 75 can easily evaporate a mobile phase consisting of 100 % H2O at less than 40°C!
Our innovative design provides performance that is superior to that obtained from systems which require a special low temperature accessory! In the top figure, the importance of low temperature evaporation is clearly demonstrated. At 39°C, a 1 µg sample of urea is barely detected, but the intensity increases by a factor of greater than 12 when the mobile phase is evaporated at 25°C, and the signal from 100 ng is clearly useful.
New update for july month! The analysis of sucralose is shown with good sensitivity in a pool of carbohydrates: feel free to take a look and request this application note for more details on the full system. SUCRALOSE SPLENDA
