1. Spectrophotometer

2. Definition :
A spectrophotometer is an instrument that measure the amount of light absorbed or transmitted by the sample.

3. Purpose : Spectrophotometer is used to:
1)measure the concentration of the solution.
2)identify organic compounds by determining the absorption maximum.

4. Principle: Spectrophotometer consists of two instruments:
1-spectrometer to produce light for any selected wave length.
2-photometer to measure the intensity of light, and the analyte is put between them.

5. Single and double beams :
In the early days of spectroscopy, double beam spectrophotometers were popular but now it is thought that the single beam spectrophotometer is more advantageous.

6. Components of single beam :

7. 1- Light source. For ultraviolet absorption spectrophotometer
for visible absorption spectrophotometer

8. For ultraviolet absorption spectrophotometer we use
# H2 lamp its wave length ranges from 190 to380 nm.

9. #D2 (deuterium) lamp its wave length ranges from185 to400 nm.
We prefer D2lamp because of its higher stability & it emits continuous radiation.

10. for visible absorption spectrophotometer we use
#tungsten lamp (350~2200nm)
#tungsten halogen lamp (240~2500nm)
We prefer tungsten halogen lamp because it has longer life, can be used at lower wave length.

12. 2- Prism or diffraction grating : Dispersion devices causes a different wavelength of light to be dispersion at different angle Optical materials : lenses. prism diffraction grating

13. 3- slit : monochromators used for selecting one wave length .

14. 4- cell (cuvette): The cuvette or absorption cells, must made from material that is transparent to radiation in the spectral region of interest.

15. 5- Detector (photometer):
a device used to convert the radiant energy to electrical signal.

16. 6- Read out device (Digital galvanometer) :
The data from the detector are displayed by a readout device , such as an analog meter ,digital display or liquid crystal display.
The out put can also transmitted to computer or printer .

17. Theoretical work of spectrophotometer:

19. Used laws:
&

20. Where
T: transmittance of solution. I: intensity of transmitted light . (Watt/cm2) Io: intensity of incident light . (watt/cm2) 𝛆 : Coefficient absorptivity. (L/mole.cm) 𝐜 : Concentration of solution. (Mole/L) : 𝐋Thickness of cuvette. (cm) A: the absorption of light by the sample

21. Beer's Law:
Beer's Law explains the relationship between absorbance, at a given wavelength and concentration.
A = 𝛆 C L
Where: A = absorbance. 𝛆 = molar absorptivity coefficient. (L/mole.cm) L = length of the light path. (cm) C = concentration of the solute. (mole/L)

23. Double Beam Spectrophotometer
It is used to measure the ratio of light intensities on two separate light paths.

24. Advantages : Wide applicability. High sensitivity. Good accuracy.
Ease and convenience.

25. Disadvantages : 1. Error in reading due to
the change in temperature
nature of solution.
2. It is subject to false wavelength setting

26. 3. an error in wavelength setting of ±0.3 nm results in an error.
4. The equipment is generally expensive.

27.  Applications in our life 
Clinical
Food and Drink
Industrial / Pharmaceutical
Life Sciences

28. Mind mapping Spectrophotometer Applications Disadvantages Advantages
Single & double beams
Double beam
Single beam
Used laws
Theoretical work
Components
cell
slit
Prism
Light source
visible UV
Principle
Purpose
Definition

29. The End
‘‘ best wishes ’’