This document discusses instruments used in plant pathology laboratories. It describes the components and operation of an autoclave, which is used to sterilize materials through high-pressure steam. The autoclave heats water to create steam at 121°C and 15 psi to kill bacteria and spores. It also explains the components and working of a spectrophotometer, which measures the absorption of light by solutions. A spectrophotometer splits light into wavelengths and detects the amount of light absorbed, allowing measurement of concentrations according to the Beer-Lambert law. These instruments are important tools for sterilization, microbial analysis, and determining chemical makeup in plant pathology research.

1. TRIBHUVAN UNIVERSITY
INSTITUTE OF AGRICULTURE AND ANIMAL SCIENCE
POST GRADUATE PROGARM
KRITIPUR, KATHMANDU
PREPARED BY:
SAGAR BHATTARAI
ROLL NO: R-2022-PLP-03M
PG Program
1st Semester, IAAS
`
INSTRUMENTS USED IN PLANT PATHOLOGY LABORATORY

2. 2
INSTRUMENTS USED IN PLANT PATHOLOGY LABORATORY
COMPONENTS OF AUTOCLAVE
 An autoclave is a instrument used in pathology laboratory which is a physical sterilization method for
killing bacteria, viruses, and even spores present in the material put inside of the vessel using steam
under pressure.
 The autoclave is considered a more effective method of sterilization as it is based on moist heat
sterilization.
 Autoclave sterilizes the materials by heating them up to a particular temperature for a specific period of
time.
 Autoclave runs in the principle of pressure cooker where the temperature reaches 121o celcius at 15lb
psi for 15 minutes.
AUTOCLAVE

3. 3
COMPONENTS OF AUTOCLAVE
Figure 1: Autoclave Parts or Components.
Image Source: pharmawiki.

4. 4
 The following is the detailed description of different components/ parts of an autoclave:
1. Chamber: The chamber is the main body of the autoclave, where the materials to be sterilized are
placed. The inner chamber is made up of stainless steel or gunmetal, the out chamber made up of an
iron case.
2. Door: The door seals the chamber and prevents steam from escaping. The lid is made airtight via the
screw clamps and asbestos washer.
3. Heating element: The heating element heats the water in the chamber, creating steam. The level of
water present in the inner chamber is vital as if the water is not sufficient; there are chances of the
burning of the heating system.
4. Thermostat: The thermostat controls the temperature of the steam.

5. 5
5. Pressure gauge: The pressure gauge measures the pressure of the steam. A pressure
gauge is present on the lid of the autoclave to indicate the pressure created.
6. Steam valve: The steam valve controls the flow of steam into the chamber.
7. Safety valve: A safety valve is present on the lid of the autoclave, which is crucial in cases
where the autoclave fails to perform its action or the pressure inside increases
uncontrollably.

6. 6
1. Check for any remaining items from the previous cycle.
2. Add sufficient water to the chamber.
3. Place the materials to be sterilized inside the chamber.
4. Close the lid tightly and switch on the electric heater.
5. Adjust the safety valves to maintain the required pressure.
6. Allow the air-water mixture to escape through the discharge tube until no more bubbles come
out.
PROCEDURE FOR HANDLING AUTOCLAVE:

7. 7
7. Close the drainage pipe and let the steam reach the desired pressure level.
8. When the whistle blows, excess pressure is released from the chamber.
9. Run the autoclave for the specified holding period (usually 15 minutes).
10. Switch off the electric heater and wait for the autoclave to cool down until the pressure gauge
shows atmospheric pressure.
11. Open the discharge pipe, remove the sterilized materials from the chamber.

8. 8
1. Always place items to be autoclaved in a secondary container.
2. Ensure items inside the chamber do not touch the sides or top of the autoclave.
3. Never attempt to open the lid while the autoclave is operating.
4. Do not autoclave liquids in sealed containers.
5. Fill liquid containers only up to 2/3rd of their volume to prevent spilling.
6. Never autoclave flammable, reactive, corrosive, toxic, or radioactive materials, household
bleach, or paraffin-embedded tissue.
7. Use materials that allow steam penetration.
PRECAUTION WHILE HANDLING AUTOCLAVE

9. SPECTROPHOTOMETER
9
 A spectrophotometer is an instrument that measures the amount of photons (the intensity of light)
absorbed after it passes through sample solution.
 With the spectrophotometer, the amount of a known chemical substance (concentrations) can also be
determined by measuring the intensity of light detected.
 This instruments is used in the process of measuring color and used for monitoring color accuracy
throughout chemical reaction.

10. PRINCIPLE OF SPECTROPHOTOMETER
10
 The basic principle is that every chemical compound absorbs, transmits, or reflects light
(electromagnetic radiation) over a certain range of wavelength.
 And spectrophotometer is made up of two instruments: a spectrometer and a photometer. The
spectrometer is to produce light of any wavelength, while the photometer is to measure the intensity of
light.
 The spectrophotometer is designed in a way that the liquid or a sample is placed between spectrometer
and photometer.

11. Cont’d
11
 The photometer measures the amount of light that passes through the sample and delivers a voltage
signal to the display.
 If the absorbing of light changes, the voltage signal also changes.
 And the change in transmitted voltage and absorbed voltage is noticed by the instrument then it
calibrates the change in terms of data which we use.
 In total the calibration is done based in the Beer-Lamberts law.

12. COMPONENTS OF SPECTROPHOTOMETER
12
A spectrophotometer, in general, consists of two devices; a spectrometer and a photometer..
1. Spectrometer: It produces a desired range of wavelength of light. First a collimator (lens) transmits a
straight beam of light (photons) that passes through a monochromator (prism) to split it into several
component wavelengths (spectrum). Then a wavelength selector (slit) transmits only the desired
wavelengths.
2. Photometer: After the desired range of wavelength of light passes through the solution of a sample in
cuvette, the photometer detects the amount of photons that is absorbed and then sends a signal to a
galvanometer or a digital display.
These will be better understood from the figure that will be displayed right after it.

13. WORKING OF SPECTROPHOTOMETER
13
Figure 2: Basic structure of spectrophotometers
(Source: Heesung Shim via LibreTexts)

14. USES OF SPECTROPHOTOMETER
 It helps in determining the chemical make-up of a substance.
 It is used in the measurement of certain ingredients that are used in making drugs to ensure that
the end product is safe for consumption by the consumers.
 It is used in microbiology to measure the rate at which bacterial growth occurs.
 Winemakers use a spectrophotometer to determine the amount of reducing sugars that are present
in a particular wine.
 It is used to determine how a certain reaction has progressed over time.
 It is used to determine the amount of concentration that a protein solution possesses.
 It helps in the measurement of solute concentrations in a solution by measuring the amount of
light that has been absorbed by the solution.
14

15. THANK YOU FOR
LISTENING!
15