Dry heat sterilisation

Question 1

Define dry heat sterilisation

Answer 1

Inactivation via oxidation - requires higher temperatures for longer periods of time
conditions need to be controlled carefully

Question 2

What is the temp range for dry heat sterilisation?

Answer 2

150-180 degrees
30mins-2hrs long
BP- 160 degrees for 2hrs

Question 3

Describe what dry heat sensitive tunnels are

Answer 3

Heated by infrared irradiation pt forced convection in laminar flow tunnels
Items sterilised on conveyer belt and pass through tunnel at 250-350 degrees

Question 4

What is dry heat sensitive tunnels mainly used for?

Answer 4

Mainly used for sterilisation and depyrogenation of glassware containers (bottles, ampoules and vials)
Materials not penetrated by steam
Metal surgical instruments (scalpels, forceps)
Substances that cannot be subjected to moisture (water-soluble powders)

Question 5

What is radiation sterilisation main target?

Answer 5

DNA
Direct damage through ionisation
Indirect damage through radiolysis of water
Resistance decreases with the presence of moisture or dissolve oxygen

Question 6

Name the 4 main types of radiation sterilisation

Answer 6

X-rays
Gamma rays
UV-light
Electron beams

Question 7

Describe gamma ray sterilisers

Answer 7

Articles passed through irradiation chamber on conveyer belt

Question 8

Give examples that gamma-ray sterilisers is used for

Answer 8

Disposable plastic e.g. Petri dishes
Decontaminate raw materials
radiation stable ointments, some solutions e.g. eye drops

Question 9

What does the BP state with gamma ray sterilisers

Answer 9

It can damage some plastics or aqueous solutions and must inside there is no product degradation

Question 10

What are the disadvantages of dry heat stabilisers?

Answer 10

Temperature needs to be higher and for longer
Large temp variations can be found
May take time to heat up
Some objects may oxidise air higher temperatures

Question 11

When is sterilisation of gases used?

Answer 11

Used for temperature-sensitive materials e.g. plastic devices with electronic (e.g. pacemaker)

Question 12

What is the disadvantages of gas sterilisation?

Answer 12

Slow
Toxic
Might need the addition of more gas as some gas might be absorbed

Question 13

What are the advantages of gas sterilisation?

Answer 13

Some processes work at room temp
Alternative for materials-sensitive to heat and/or radiation

Question 14

Name the 2 gases used for gas sterilisation

Answer 14

Ethylene oxide (alkylating agent)
Formaldehyde (alkylating agent and cross-linker)

Question 15

What are the key properties of ethylene oxide?

Answer 15

BP -11 degres
Toxic, vesicant and carcinogen
Readily absorbed by plastics and fabrics
Highly flammable

Question 16

What are the advantages of ethylene oxide?

Answer 16

Can act at RT
Bactericidal
Broad spectrum

Question 17

What are the disadvantages of ethylene oxide?

Answer 17

Difficult and potentially dangerous
Need to be stored in a safe area after sterilisation as there is a risk of gas dispersing out
Expensive

Question 18

What are the properties of formaldehyde?

Answer 18

BP - -19 degrees
37% aqueous solution used as a disinfectant and prevention of biological specimens
Gas obtained by heating formalin and steam to low-temperature steam formaldehyde
Not flammable

Question 19

What are the advantages of formaldehyde?

Answer 19

Bactericidal
Non-flammable explosive
Broad spectrum, non-selective

Question 20

What are the disadvantages of formaldehyde?

Answer 20

Toxic - need to store in safe area after sterilisation
Low penetration power
May leave residues of polymers
Slow-acting

Question 21

What is the mechanisms of filtration?

Answer 21

Adsorption
Sieving
Trapping in the filter matrix