The document discusses different types of detectors used in HPLC. It describes 4 detectors in detail: [1] UV detector, which detects compounds that absorb UV light; [2] Fluorescence detector, which detects compounds that fluoresce under light; [3] Electrochemical detector, which detects compounds that can be oxidized or reduced; [4] Thermal conductivity detector (TCD), which detects changes in thermal conductivity of the mobile phase. The document provides information on the principles, operation, applications and advantages of these four important HPLC detectors.

1. JSPM’S
Charak College Of Pharmacy & Research
Gat no.720/1&2, Wagholi, Pune-Nagar Road,wagholi,
pune -412207
Detection of HPLC
Presented By, Guided By,
Miss. Shradha Jedge Dr. Rajesh J Oswal
Prof.Sandip Kshirsagar
Department Of Pharmaceutical Chemistry

2. Detection of HPLC

3. INDEX
 INTRODUCTION
 TYPES
 WORKING OF HPLC

4. WORKING OF HPLC

5. WHAT IS DETECTOR
An instrument use to detect or observe.
 selection of detector is on the basis of analyze
or sample under detection.
 visualize components of the mixture being
eluted off the chromatography column.

6. Properties of detector
 Low drift and noise level (particularly crucial in trace
analysis).
 High sensitivity, Fast response, Operational simplicity
and reliability, non-destructive, inert (non-reactive)
 Produce uniform, reliable and reproducible detection
and analytic data.
 Compatible for all types of compounds under testing.
 Wide linear dynamic range (simplifies quantization).
 Low dead volume (minimal peak broadening).
 Cell design which eliminates remixing of the separated
bands.
 Insensitivity to changes in type of solvent, flow rate.
 It should be tunable so that detection can be optimized
for different compounds.

7. Types of
Detector
Destructive Non destructive

8. 1) Flame ionization detector.
2) Flame photometric
detector, FPD..
Destructive
3) mass spectrometer.
4) Nitrogen Phosphorus Detector,
5) Evaporative light scattering
detector (ELD).
1) Thermal conductivity
detector, (TCD)
Non destructive 2) Fluorescence detector
3) Electron Capture
Detector, ECD
4) UV detectors,

9. 1) UV DETECTOR
Ultra-Violet (UV) detectors measure the ability of a sample to
absorb light.
This can be accomplished at one or several wavelengths.
 sensitivity to approximately 10-8 or 10 -9 gm/ml.
TYPES OF UV-
DETECTOR
A) Fixed Wavelength
measures at one wavelength, usually 254 nm
B) Variable Wavelength
measures at one wavelength at a time, but can
detect over a wide range of wavelenths.
C) simulateneously wavelengths
Diode Array

10. UV detectors
 Depends on absorption of UV ray energy by the sample.
 When the UV rays emitted by lamp pass through gratings,
rays split into different wavelengths. One specific
wavelength rays are passed through sample. Some amount
of light is absorbed by sample and the unabsorbed rays
which fall on photo cell.
 These rays on collision on photo cell produces electrons
whose current is recorded.
 This is indicative of nature and quantity of sample. This UV
wavelength range of absorption is specific for sample .
 They are capable to detect very wide range of compounds.
 The sensitivity ranges till microgram quantity of estimation.

12. 2) FLUORESCENCE DETECTOR
fluorescence rays emitted by sample after absorbing incident light is measured as a
function of quality and quantity of the sample
Xenon arc lamp is used to produce light for excitation of sample molecules.
These light rays excite the sample molecules. These excited molecules emit
florescence, which pass through gratings. These gratings pass the florescence
at specific wavelength to photo cell which is recorded.
The detector is suitable for compounds which can produce florescence.
they have high precision and sensitivity (with less noise in data).

13. 3) ELECTROCHEMICAL DETECTOR
This detector is specially suitable to estimate oxidisable & reducible
compounds.
principle :
when compound is either oxidized or reduced, the chemical reaction
produces electron flow. This flow is measured as current which is the
function of type and quantity of compound.
This electrode is suitable for compounds which can't be assayed by UV
detector especially due to their similarities in light absorption
properties ex: monoamines.
This detector has super sensitivity which ranges till picograms
measurement.

14. ELECTROCHEMICAL DETECTOR

15. 4) THERMAL CONDUCTIVITY DETECTOR
(TCD)
 chemical specific detector commonly used gas-liquid chromatography.
This detector senses changes in the thermal conductivity of the column
effluent and compares it to a reference flow of carrier gas.Since most
compounds have a thermal conductivity much less than that of the
common carrier gases of helium or hydrogen, when an analyte elutes
from the column the effluent thermal conductivity is reduced, and a
detectable signal is produced.
Operation
The TCD consists of an electrically heated filament in a temperature-
controlled cell. Under normal conditions there is a stable heat flow from
the filament to the detector body. When an analyte elutes and the thermal
conductivity of the column effluent is reduced, the filament heats up and
changes resistance. This resistance change is often sensed by a
Wheatstone bridge circuit which produces a measurable voltage change.
The column effluent flows over one of the resistors while the reference flow
is over a second resistor in the four-resistor circuit.

16. Since all compounds, organic and inorganic, have a thermal
conductivity different from helium, all compounds can be detected
by this detector. The TCD is often called a universal detector
because it responds to all compounds. Also, since the thermal
conductivity of organic compounds are similar and very different
from helium, a TCD will respond similarly to similar
concentrations of analyte. Therefore the TCD can be used without
calibration and the concentration of a sample component can be
estimated by the ratio of the analyte peak area to all components
(peaks) in the sample.

17. 5) flame ionization detector (FID)
As the name suggests, analysis involves the detection of ions. The source of these
ions is a small hydrogen-air flame.
Sometimes hydrogen-oxygen flames are used due to an ability to increase
detection sensitivity, however for most analysis, the use of compressed
breathable air is sufficient.
The resulting flame burns at such a temperature as to pyrolyze most organic
compounds, producing positively charged ions and electrons.In order to detect
these ions, two electrodes are used to provide a potential difference.
The positive electrode doubles as the nozzle head where the flame is produced.
The other, negative electrode is positioned above the flame. When first
designed, the negative electrode was either tear-drop shaped or angular piece of
platinum.
Today, the design has been modified into a tubular electrode, commonly referred
to as a collector plate. The ions thus are attracted to the collector plate and upon
hitting the plate, induce a current. This current is measured with a high-
impedance picoammeter and fed into an integrator
How the final data is displayed is based on the computer and software. In
general, a graph is displayed that has time on the x-axis and total ion on the y-
axis.The current measured corresponds roughly to the proportion of reduced
carbon atoms in the flame.
Specifically how the ions are produced is not necessarily understood, but the
response of the detector is determined by the number of carbon atoms (ions)

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