DETECTORS IN HPLC

In this slide contains principle and types of detectors used in HPLC.
Presented by: K.Tarun. (Department of industrial pharmacy).
RIPER, anantpur.

1. 1 DETECTORS IN HPLC A seminar as a part of curricular requirement for I year M. Pharm I semester Presented by K. Tarun (20L81S0805) Dept. of Industrial Pharmacy Under the guidance/Mentorship of Dr. Hindustan Abdul Ahad M. Pharm, Ph.D , FAGE Life member of IPA & APTI Professor & Head, Dept. of Industrial Pharmacy

2. 2 Introduction Principle Types of detectors List of Detectors Conclusion Reference Contents:

3. 3 A chromatography detector is a device to detect components of the mixture being eluted off the chromatography column. Properties: Low drift and noise level. High sensitivity. Fast response. Wide linear dynamic range. Low dead volume (minimal peak broadening). It should be non-destructive. Introduction:

4. 4 HPLC is based on adsorption as well as partition chromatography. It is depends on the nature of stationary phase. Determination of volatile and non-volatile compounds. Principle:

5. 5

6. 6 UV-visible Detector Fixed / Single Wavelength Detector Variable Wavelength Detector Photodiode Array Detector / DAD Refractive Index Detector Fluorescence Detector Electrochemical Detector Conductivity Detector / Potentiometry Evaporative Light Scattering Detector (ELSD) Mass Detector (LC-MS) IR Detector Optical Rotation Detector (ORD) / Chiral Detectors Corona Discharge Detectors List of detectors:

7. 7 1. UV-Visible Detector: They give specific response to the class of compounds or particular compounds depending upon the functional group of eluting molecules. When the light of a certain wavelength is directed at a flow cell, the substance inside the flow cell absorbs light. These detectors are different types:

8. 8 Such type of detectors does not allow change in wavelength of the radiation. Absorbance of only one given wavelength is monitored by the system at all times (usually 254nm). Limited in flexibility. Simplest & Cheapest of the UV/Visible. a. Fixed Wavelength Detector:

9. 9 These can be adjusted to work on any wavelength over full UV-Visible region. The wavelength can be selected at 3nm or less. More expensive. More versatile. b. Variable Wavelength Detector:

10. 10 Light from the broad emission source such as deuterium lamp. It is collimated by an achromatic lens system. So that the total light passes through the detector cell onto a holographic grating. The dispersed light from the grating is allowed to fall on to a diode array. c. Photodiode Array Detector:

11. 11 Refractive index detector measures the molecule’s ability to deflect light in a flowing mobile phase in a flow cell relative to a static mobile phase contained in a reference cell. The amount of detection is proportional to the concentration of the solute in the mobile phase. 2. Refractive Index Detector:

12. 12 The are different types are: Deflection refractometer Fresnel refractometer Interferometer detectors Mostly used for detection of non-ionic compounds that neither fluorescence nor absorb in the UV region. Draw backs: Less sensitive Temperature control Less suitability to gradient elution.

13. 13 Fluorescence is 10-1000 times sensitive than UV detector for strong UV absorbing compounds. Even a single analyte in the cell can be detected by the fluorescence detector. The system is easy to operate and relatively stable. Sensitivity depends on the fluorescence properties of the components in the elute. 3. Fluorescence Detector:

14. 14 Fluorescence Detector

15. 15 There are 3 types of fluorescence detectors:

16. 16 Usually measure the current associated with the oxidation or reduction of solutes. They are sensitive to changes in the flow rate or composition of the eluent. The level of current is directly proportional to the analyte concentration. Three electrodes are employed which are: Working electrode Auxiliary electrode Reference electrode 4. Electrochemical Detector:

17. 17 It is used in analytical applications for the detection of ionic compounds. Measures the ability of the mobile phase to conduct a current when placed in a flow-cell between 2 electrodes. Measured Value is directly proportional to the concentration of ions present in the solution. 5. Conductivity Detector:

18. 18 It is useful for large molecular weight molecules like surfactants, lipids and sugar. Detection is based on the scattering of a beam of light by particles of compound remaining after evaporation of the mobile phase. It is a universal detector Does not required a compound to have a chromophore for detection. There are 3 steps involved in detection: Nebulization Mobile phase evaporation Detection 6. Evaporative Light Scattering Detector (ELSD):

19. 19 The mobile phase which must be volatile. The flow from the column is nebulized with a stream of inert gas. The particles are passed through a laser beam and they scatter the laser light. The scattered light is measured at right angles to the laser beam by a photodiode detector.

20. 20 The detection by mass spectrometers is based on molecular fragmentation by electric fields. Separation is based on the mass to charge ration of the fragmented molecule. It is a method that combines separation power of HPLC with detection power of mass spectrometry. They show high selectivity & sensitivity. In LC-MS technique advantage of resolution and sensitivity. The analyte for mass spectrometer must be in ionic form. 7. Mass Spectrometer:

21. 21 Mass Spectrometer

22. 22 Infrared detectors are chosen on the basis of property of compound to absorb infrared light. It is a sophisticated instrument and requires Cells or windows made of NaCl or CaF 2 . The wavelength scanning is provided by semicircular filter wedges, the wavelength range from 4000-690 cm-1. The detector is suitable for polymer analysis. Not very sensitive Mobile phase solvents absorb strongly in the IR region. 8. IR Detector:

23. 23 Used for detection of optically active compounds such as amino acids, sugars & terpenes containing an asymmetric carbon. There are 2 chiral detection techniques: Polarimetry / optical rotary dispersion (ORD) Circular dichroism (CD) ORD detectors are based on differences in refractive index. CD differentiate enantiomers by measuring differences between the absorption of light & left handed circularly polarized light due to existence of a chiral chromophore. 9. Optical Rotation Detector (ORD) / Chiral Detectors:

24. 24 Optical Rotation Detector

25. 25 Other name for this is Charged Aerosol Detection (CAD). It is a newer and unique technique. The HPLC column eluent is first nebulized with a nitrogen (or air) carrier gas to form droplets which are then dried to remove mobile phase, producing analyte particles. The analytes then are further transferred to a collector where it is measured by a highly sensitive electrometer. 10. Corona Discharge Detector:

26. 26 Charged Aerosol Detection

27. 27 The work of the detector is to detect and give the evidence to the recorder which shows it in a form of a chromatogram. It senses at a more rapidly. Each compound has its properties that are not the same as one another, thus arises a need to have different detectors for different compounds. Conclusion:

28. 28 Swartz M. HPLC detectors: a brief review. Journal of Liquid Chromatography & Related Technologies. 2010 Jul 13;33(9-12):1130-50. Sunil A, Anju G, Rajat V. HPLC Detectors, Their Types and Use: A Review. Organic & Medicinal Chemistry International Journal. 2018;6(5):143-6. Sims JL, Carreira JA, Bragg RA. Optical rotation detection for reversed phase HPLC: Investigation of solvent effects. Chirality. 1997;9(2):122-5. Sagliano Jr N, Hartwick RA. Micro-HPLC detectors: a review. Journal of chromatographic science. 1986 Nov 1;24(11):506-12. References:

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