An evaporative light scattering detector (ELSD) is a detector used or analysis of compounds where UV detection might be a restriction and therefore used where compounds do not efficiently absorb UV radiation, such as sugars, antivirals, antibiotics, fatty acids, lipids, oils, phospholipids, polymers, surfactants, terpenoids and triglycerides.ELSDs is related to the charged aerosol detector (CAD) and like the CAD, falls under the category of destructive detectors.

1. Evaporative Light Scattering Detector
(ELSD)
By:
Amol Sagulale
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2. Agenda
1) Theory and Principle of Operation:
• Nebulization
• Evaporation
• Detection
• Scattering mechanism
2) Advantages
3) Limitations
4) Applications
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3. 3
Nebulization

4. Nebulization region and drift tube
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10. Evaporation
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12. Detection
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13. •Light source imparts on the particles, light is thus
scattered and focused onto a photomultiplier tube (PMT),
where its intensity is measured.
•Size (diameter) – determines how the light is scattered.
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14. •PMT converts-scattered light signal –voltage that can be
recorded and analyzed.
•Stronger the scattering-more intense signal
•Intensity of scattered light-function of the mass of the
scattering particles –follows an exponential relationship-
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17. •Ratio of particle diameter (D), to the incident wavelength
λ, or D/λ defines the the type of scattering that results….
•Rayleigh scattering –smallest particles where D/λ < 0.1
•Mie scattering –particles where D/λ > 0.1 but < 1.0
•Refraction-reflection scattering –particles where D/λ >
1.0
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18. Advantages
•5 to 10 times more sensitive than RI Detector
•Support the use of gradient elution method
•Not easily affected by changes in the ambient
temperature
•Not affected by interference due to solvent peak
•Not required to allow for the instrument & the
baseline to stabilize
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19. Limitations of ELSD
•ELS detection lacks linearity over wide range of
concentration ranges.
•ELS detection is a destructive technique, analyte generate
the scattering particles.
•Any particle can interfere with the sample signal-poor
grade solvents-responds equally to all particles.
•The detector’s sensitivity to the particulates increases
noise.
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20. Limitations of ELSD
•Sensitivity-
•Small molecule is limited to 1-50 ng on column
in the best instances.
•Limit of detection- 50 – 100 ng generally
observed
•Amount suitable for many analyses but could fall
short for some needs
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•Digital Signal functions are
accessed via the down arrow key
in main menu screen
• Parameter Screen allows you to
change
- PMT output or gain (1-250)
- Smoothing (1-50)
- LED intensity (0-100)
•Digital Signal functions are
accessed via the down arrow key
in main menu screen
• Parameter Screen allows you to
change
- PMT output or gain (1-250)
- Smoothing (1-50)
- LED intensity (0-100)
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29. Applications
•ELSDs are capable of analyzing all substances that have
an evap. temp lower than lower-mobile phase.
•Can attain roughly the same level of detection sensitivity
for any compound.
•For this reason, -well suited-detection-sugars, fats,
surfactants, synthetic macromolecules and steroids-have
low UV light absorbance –making them difficult to detect
with UV detector.
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30.
Thank You
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