Evaporative Light-Scattering Detectors (ELSD)

The principle of LT-ELSD

The LT-ELSD process can be divided into three critical phases, each of which takes place in different parts of the detector: Nebulization, Evaporation and Detection.

In LT-ELSD, the mobile phase enters the detector, where it is nebulized with pure gas and then vaporized in a drift tube. The remaining dissolved particles are detected by the scattering of an incident light beam.

The intensity of the scattered light is influenced by the size of the suspended particles, which in turn depends on the size of the droplets formed by the nebulizer and the concentration of the dissolved substances in these droplets. The droplet size generated by the nebulizer is determined by the physical properties of the liquid and the relative velocity of the gas and liquid flows.

These interdependent factors highlight the importance of precise design and careful optimization of the individual components in SEDEX detectors.

Nebulize the eluent and select small droplets

The eluent from the column is combined with an inert gas and passed through the narrow opening of the nebulizer, creating a uniform mist. This mist consists of tiny droplets of the mobile phase containing the target compound.

SEDEX LT technology then allows droplets to be selected based on size, ensuring that larger droplets do not enter the evaporation tube. Exclusion of larger droplets is critical as they require higher drying temperatures and contribute to increased background noise.

Evaporation of the mobile phase at low temperature

The nebulized eluent passes through a heated drift tube in which the mobile phase is evaporated.

The dissolved molecules are isolated from the mist in this heated evaporation tube, which operates at a low temperature. The SEDEX detectors are specially designed to efficiently vaporize mobile phases with high boiling points at minimum temperatures. This unique feature reduces the risk of thermal decomposition or evaporation of the compounds of interest and makes SEDEX LT technology a highly reliable method for detecting all components in the sample.

Detection of the scattered light

The flow of solid analyte particles is directed into a detection chamber containing the light source and a photomultiplier or photodiode. The dissolved molecules are hit with an incident light beam and the scattered light is measured. The intensity of the light scattered by the particles is proportional to the mass of the eluted compound.

At this step gas-assisted focusing (GSF), which is a secondary gas inlet flow, helps to concentrate the solute particles into the centre of the optical head to improve detection sensitivity and to prevent this part from any contamination.

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SEDEX LT-ELSD 90LT - The Ultimate

The SEDEX LT-ELSD 90LT is an evaporative light scattering detector known for its high sensitivity, reliability, and accuracy in detecting various compounds. This detector utilizes cutting-edge low-temperature evaporation technology and features a unique optical head built on laser technology, delivering exceptional performance for HPLC and UHPLC applications. 

Key features include:

• Low-temperature evaporation of the mobile phase
• Improved sensitivity up to the mid-picogram level
• Digital signal treatment
• Complete Remote Control
• Dynamic range of over five orders of magnitude

The SEDEX LT-ELSD 90LT can be easily integrated into almost any HPLC system, since it can be controlled locally via the keypad and display or remotely via USB using drivers for various CDS software packages, including ClarityChrom®, OpenLAB® or Chromeleon™. Detailed SOP protocols for GLP compliance and validation procedures are available.

For this model you can choose from four different nebulizers, each specifically optimized for HPLC, UHPLC or Low Flow and Micro Flow applications.

SEDEX LT-ELSD 85LT - The Standard

The SEDEX LT-ELSD 85LT is an industry-standard evaporative light scattering detector known for its excellent sensitivity, reliability, and accuracy in detecting various compounds. This detector employs low-temperature evaporation technology and features specialized nebulizers, delivering optimal performance for basically any LC application.

Key features include:

• Low-temperature evaporation of the mobile phase
• Choice of six nebulizers
• Complete Remote Control

The SEDEX LT-ELSD 85LT can be easily integrated into almost any HPLC system, since it can be controlled locally via the keypad and display or remotely via USB using drivers for various CDS software packages, including ClarityChrom®, OpenLAB® or Chromeleon™. Detailed SOP protocols for GLP compliance and validation procedures are available.

For this model you can choose from six different nebulizers, each specifically optimized for HPLC, UHPLC, Low Flow, Micro Flow, SFC or Combinatorial Chemistry applications.

SEDEX LT-ELSD 80LT - The Cost-Effective

The SEDEX LT-ELSD 80LT is a cost-effective evaporative light scattering detector known for its great sensitivity, reliability, and accuracy in detecting various compounds. This detector employs low-temperature evaporation technology and is designed to offer users a simple experience without sacrificing fidelity and performance.

Key features include:

• Low-temperature evaporation of the mobile phase
• Digital signal treatment
• Complete Remote Control

The SEDEX LT-ELSD 80LT can be easily integrated into almost any HPLC system, since it can be controlled locally via the keypad and display or remotely via RS-232 using drivers for various CDS software packages, including ClarityChrom®, OpenLAB® or Chromeleon™. Detailed SOP protocols for GLP compliance and validation procedures are available.

For this model you can choose from three different nebulizers, each specifically optimized for HPLC, Flash chromatography or Combinatorial Chemistry applications.

SEDEX LT-ELSD LC - The Cutting-Edge

The SEDEX LT-ELSD LC is an evaporative light scattering detector that offers unprecedented fidelity, sensitivity and accuracy in detecting various compounds. This detector utilizes cutting-edge low-temperature evaporation technology and combines innovative features to provide superior optical and electronic performance at a competitive price. It is specifically suited for standard liquid chromatography. Take advantage of the SAGA (SEDEX Automated Gain Adjustment) system that will automatically adjust the gain to prevent the detector from saturating and going off-scale.

Key features include:

• Low-temperature evaporation of the mobile phase
• Innovative SAGA technology
• Complete Remote Control
• Single, dedicated nebulizer and innovative cell design

The SEDEX LT-ELSD LC can be easily integrated into almost any HPLC system, since it can be controlled locally via the keypad and display or remotely via USB using drivers for various CDS software packages, including ClarityChrom®, OpenLAB® or Chromeleon™. Detailed SOP protocols for GLP compliance and validation procedures are available.

This model is equipped with a dedicated nebulizer for HPLC applications.

SEDEX LT-ELSD FP - The Purification Mate

The SEDEX LT-ELSD FP is an evaporative light scattering detector that combines reliability, robustness, and simplicity for exceptional purification performance. This detector is specifically designed to meet the needs of preparative HPLC, preparative SFC, as well as Flash Chromatography, and offers a cost-effective solution for detecting various compounds during purification. The SEDEX LT-ELSD FP utilizes innovative low-temperature evaporation technology and features an optimized liquid flow path. Take advantage of the SAGA (SEDEX Automated Gain Adjustment) system that will automatically adjust the gain to prevent the detector from saturating and going off-scale.

Key features include:

• Low-temperature evaporation of the mobile phase
• Innovative SAGA technology
• Complete Remote Control
• Dedicated nebulizer and innovative cell design

The SEDEX LT-ELSD FP can be easily integrated into almost any HPLC system, since it can be controlled locally via the keypad and display or remotely via USB using drivers for various CDS software packages, including ClarityChrom®, OpenLAB® or Chromeleon™. Detailed SOP protocols for GLP compliance and validation procedures are available.

This model is equipped with a dedicated flash nebulizer for preparative chromatography applications.

Nebulize the eluent and select small droplets

The eluent from the LC column is combined with an inert gas and passed through the narrow opening of a nebulizer, transforming the mobile phase into a uniform mist of tiny droplets containing the target compound.

SEDEX LT technology allows droplets to be selected based on size, ensuring that larger droplets do not enter the evaporation tube. Exclusion of larger droplets is critical as they require higher drying temperatures and contribute to increased background noise. Smaller droplets are advantageous as lower temperatures are required for evaporation of the eluent, thus enhancing detection efficiency and performance.

Evaporation of the mobile phase at low temperature

The nebulized eluent (droplets) are carried by the gas flow into a heated drift tube in which the mobile phase is completely evaporated to produce particles of the solute compound.

The SEDEX detectors are specially designed to optimize evaporation efficiency at minimal temperatures. With a typical operating range of 30°C to 60°C these drift tubes are capable of sufficiently evaporate most solvents used in HPLC and even mobile phases with high boiling points. This unique feature minimizes the risk of thermal decomposition or evaporation of the compounds of interest and makes SEDEX LT technology a highly reliable and efficient method for detecting all components in the sample.

Detection of the scattered light

The flow of solid analyte particles is directed into a detection chamber containing the light source and a photomultiplier or photodiode. The dissolved molecules are hit with an incident light beam and the scattered light is measured. The intensity of the light scattered by the particles is proportional to the mass of the eluted compound.

At this step gas-assisted focusing (GSF), which is a secondary gas inlet flow, helps to concentrate the solute particles into the centre of the optical head to improve detection sensitivity and to prevent this part from any contamination.

Low-Temperature evaporation technology for high sensitivities

The innovative design of the SEDEX LT-ELSD nebulization cell enables to select droplets based on size. Large droplets are harder to evaporate and need higher temperatures, therefore would contribute to increased noise levels. In the glass nebulization cell of the SEDEX LT-ELSD devices, the largest droplets are effectively discarded, allowing for lower operating temperatures without compromising sensitivity (signal-to-noise ratio).

The diagram below illustrates how droplet size selection works. The nebulizer generates a mist containing droplets of various sizes. The nebulization cell acts as a true size exclusion selector, so that the largest droplets (highlighted in blue in the figure) are removed to waste. Only droplets smaller than a size limit are permitted to enter the evaporation tube (highlighted in green in the figure).

This droplet selection is a unique feature of SEDEX LT-ELSD and ensures genuine low-temperature evaporation and delivers exceptional sensitivity across all compound types.

Other ELSDs on the market lack this kind of droplet selection and thus rely on higher temperatures for evaporation to achieve acceptable noise levels, resulting in significantly reduced sensitivity for semi-volatile and thermo-labile compounds. 

Headline headline head

I am a dummy copy. And I´ve been a dummy copy since my birth. It took me a long time to realize what it means to be a dummy copy: you make no sense. You stand out now and then by being completely out of context. Often, you aren´t even read at all. But does that make me a bad copy? I know that I´ll never stand a chance of appearing in the Economist.

But does that make me any less important? I´m a dummy! But I enjoy being a copy. And should you now decide to carry on reading me to the end, I´ll have managed to achieve something most „normal“ copies don´t achieve.

Headline headline head

I am a dummy copy. And I´ve been a dummy copy since my birth. It took me a long time to realize what it means to be a dummy copy: you make no sense. You stand out now and then by being completely out of context. Often, you aren´t even read at all. But does that make me a bad copy? I know that I´ll never stand a chance of appearing in the Economist.

But does that make me any less important? I´m a dummy! But I enjoy being a copy. And should you now decide to carry on reading me to the end, I´ll have managed to achieve something most „normal“ copies don´t achieve.

Headline headline head

I am a dummy copy. And I´ve been a dummy copy since my birth. It took me a long time to realize what it means to be a dummy copy: you make no sense. You stand out now and then by being completely out of context. Often, you aren´t even read at all. But does that make me a bad copy? I know that I´ll never stand a chance of appearing in the Economist.

But does that make me any less important? I´m a dummy! But I enjoy being a copy. And should you now decide to carry on reading me to the end, I´ll have managed to achieve something most „normal“ copies don´t achieve.

Headline headline head

I am a dummy copy. And I´ve been a dummy copy since my birth. It took me a long time to realize what it means to be a dummy copy: you make no sense. You stand out now and then by being completely out of context. Often, you aren´t even read at all. But does that make me a bad copy? I know that I´ll never stand a chance of appearing in the Economist.

But does that make me any less important? I´m a dummy! But I enjoy being a copy. And should you now decide to carry on reading me to the end, I´ll have managed to achieve something most „normal“ copies don´t achieve.

Headline headline head

I am a dummy copy. And I´ve been a dummy copy since my birth. It took me a long time to realize what it means to be a dummy copy: you make no sense. You stand out now and then by being completely out of context. Often, you aren´t even read at all. But does that make me a bad copy? I know that I´ll never stand a chance of appearing in the Economist.

But does that make me any less important? I´m a dummy! But I enjoy being a copy. And should you now decide to carry on reading me to the end, I´ll have managed to achieve something most „normal“ copies don´t achieve.

Headline headline head

I am a dummy copy. And I´ve been a dummy copy since my birth. It took me a long time to realize what it means to be a dummy copy: you make no sense. You stand out now and then by being completely out of context. Often, you aren´t even read at all. But does that make me a bad copy? I know that I´ll never stand a chance of appearing in the Economist.

But does that make me any less important? I´m a dummy! But I enjoy being a copy. And should you now decide to carry on reading me to the end, I´ll have managed to achieve something most „normal“ copies don´t achieve.