EVAPORATIVE LIGHT SCATTERING DETECTOR

(ELSD)

ANALATYCAL CHEMISTRY427 PHC

Done by:Madawi AlUbied Areej Alsuwayyid

OBJECTIVES

1. What is Evaporative Light Scattering Detector ?

2. Capabilities

3. how does it work?

4. Characteristic properties

5. Advantages

6. Sensitivity

7. Problems

1. WHAT IS EVAPORATIVE LIGHT SCATTERING

DETECTOR ?• Evaporative Light Scattering

Detectors (ELS Detectors) are

essentially universal detectors.

• primarily used in High Performance

Liquid Chromatography (HPLC).

• ELS detectors are an ideal substitute,

or supplement to, traditional HPLC

detectors for liquid chromatography

concentration detection.

2. CAPABILITIES

• The detector responds to all compounds that are, relative to their mobile phase, sufficiently nonvolatile at the conditions of analysis.

• ELSD is suitable for all LC separated analyses that does not have light absorbing chromophores.

So it dose not rely on optical properties .

Ex:

phospholipids, carbohydrates, amino acids , fatty acids and synthetic polymers.

3. HOW DOES IT WORK?

3 key stages:

1

2

3

STAGE 2: EVAPORATION

4 .CHARACTERISTIC PROPERTIES

I. Low background noise (no solvent peaks)

II. Reproducibility (in the 1μg range, STD ~ 1%)

III. Low band broadening (short transit time)

IV. “Near” linear response (instrument and concentration dependent, smart choice of stand)

5 .ADVANTAGES

1. No sample preparation

2. No drivatisation

3. Universal - responds to all compounds in the mobile phase

4. Not dependent on spectroscopic properties of analyte

5. Not susceptible to baseline drift during gradient elution, temperature or solvent pump fluctuations

6. ELSD compatible with a much wider range of solvents compared to Refractive Index detector

7. No interference from solvent front peaks (enables fast analysis)

8. Flow rates up to up to 5ml/min can be achieved with no affect on baseline stability

9. Ideal for High Throughput Screening and quantification

THE ELSD IMPROVES BASELINE STABILITY AND DETECTION SENSITIVITY COMPARED

TO RI

10278

10277

Column: Prevail™ Carbohydrate ES, 5µm, 53 x 7mm (Part No. 35104)

Mobile Phase: Acetonitrile:Water (75:25) Flowrate: 2.0mL/min

ELSD

RI

1. Fructose2. Glucose3. Sucrose

6. SENSITIVITY

Sensitivity with ELSD is limited to 1–50 ng on-column in the best instances.

the followings factors are considered to be affect ELSD sensitivity :

• Gas quality

• Solvent quality

• Column contributions

• Solvent modifiers

7. PROBLEMS:

arising with an ELSD are usually manifest in a noisy baseline. This can have several causes:

1. Evaporation Temperature too low: the solvent is not completely evaporated.

2. Evaporation Temperature too high: the solvent is boiling in the nebuliser.

3. Air or nitrogen not clean: remove traces of water or oil with a filter.

4. Gas flow too low: poor nebulisation of the eluent.

Involatile material in the eluent: replace any buffer salt with a volatile one (such as ammonium acetate) and ensure that the eluent is particle free.

REFERENCES

• http://www.usedhplc.co.uk/UsedHPLC-IntroductiontoEvaporativeLightScatteringDetectorsELSD.htm

• http://www.separationsnow.com/details/ezine/sepspec10174ezine/Exploring-the-alluring-charms-of-a-charged-aerosol-detector-for-HPLC.html?tzcheck=1

• http://www.laserchrom.com/LaserchromHPLC-TechnicalSupportCentre-TechnicalTips-IntrotoELSD.htm

• http://fxg-ent.com/downloads/SoftaELSDBrochure.pdf