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The LT-ELSD chromatography

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Low Temperature Evaporative Light Scattering Detection (LT ELSD)

A Universal Detection Technique for Modern Chromatography

The Low Temperature Evaporative Light Scattering Detector (LT ELSD) is a universal, mass dependent detection technique designed for compounds that are less volatile than the mobile phase. Unlike UV, fluorescence or electrochemical methods, LT ELSD does not require chromophores, electroactive groups or specific optical properties. This makes it ideal for detecting a wide variety of analytes — including carbohydrates, lipids, surfactants, polymers, peptides, and many compounds undetectable by conventional detectors. The detector response is directly proportional to the mass of the eluted compound, giving highly consistent response factors for structurally related molecules and enabling quantification even when reference standards are not available.
LT ELSD is fully compatible with gradient mobile phases, since the mobile phase is evaporated before optical detection takes place. Complex samples can therefore be separated using a wide range of buffers or modifiers such as AcONH₄, AcOH, HCOONH₄, HCOOH, NH₄CO₃, TFA, HFBA or triethylamine — without compromising sensitivity or stability.

Step 1: Nebulization — Creating a Fine, Stable Aerosol

The eluent is mixed with an inert gas and forced through a precision nebulizer to generate a homogeneous mist of fine droplets.
SEDEX LT ELSD technology selectively removes large droplets before they reach the evaporation zone, preventing noise, improving signal to noise ratio and avoiding unnecessary heating. This step ensures clean aerosol generation, optimal particle size distribution and excellent baseline stability.

Step 2: Low Temperature Evaporation — Preserving Sensitive Molecules

The nebulized aerosol travels through a heated drift tube, where the mobile phase is fully evaporated.
SEDEX detectors are engineered to evaporate even high boiling point solvents at exceptionally low temperatures, preventing thermal degradation of semi volatile or heat sensitive analytes.
This low temperature capability is a unique strength of SEDEX technology, ensuring gentle treatment of fragile molecules.
Compared to systems requiring specialized cooling devices, SEDEX provides superior performance with a simpler, more reliable architecture.

Step 3: Detection — Measuring Scattered Light with High Precision

The dried particles enter the detection cell, where a laser or light source illuminates them. A photodiode or photomultiplier measures the intensity of scattered light, which is directly correlated to analyte mass. SEDEX detectors feature Gas Supported Focusing (GSF™), a patented technology that focuses particles inside the optical head, increasing sensitivity, reproducibility and safety.
This configuration enables detection of ultra low concentrations while preserving the integrity of semi volatile or thermolabile compounds.

Why Low Temperature Evaporation Matters

Temperature is the most critical optimization parameter in any ELSD.
If evaporation temperature is too high, semi volatile analytes may evaporate entirely or degrade, resulting in signal loss.
SEDEX LT ELSD detectors ensure:

• Efficient evaporation of high boiling solvents at low temperatures

• Maximum protection for thermolabile compounds

• Superior sensitivity without thermal artefacts

• Wide compatibility with aqueous, organic and buffered mobile phases

Broad Compatibility Across Chromatographic Techniques

SEDEX LT ELSD detectors are fully compatible with:

• HPLC, UHPLC, µ HPLC

• HTLC

• GPC / SEC

• Flash Chromatography

• Counter Current Chromatography (CCC)

• Supercritical Fluid Chromatography (SFC)

• Preparative and semi preparative LC

They deliver excellent sensitivity and stability for both analytical and preparative workflows.