Sterilisation 4 Flashcards
autoclave, mechanism of heat transfer?
Latent heat of vaporization- steam comes into contact with the object in the chamber and condenses round the object as it does this theres a small vacuum round the product that sucks in more steam and the heat is transferred from the steam to the product- as a result this creates more of a vacuum
This continues till the heat is the same
what are the critical aspects of autoclaving?
Air Removal- to replace the air with steam to pressurize the container if you don’t you’re unlikely to get temperatures above 100 degrees.
Saturated Steam- has a defined moisture content
Steam under pressure- only when the steam is generated under pressure will it get hotter than 100 degrees which we need to remove endospores
what would happen if you dont remove the air?
unlikely to get temperatures above 100 degrees
why does the steam need to be under pressure
only when the steam is generated under pressure will it get hotter than 100 degrees which we need to remove endospores
what is filtration sterilisation
passage of fluid across a filter, removing contaminating solutes
what is a filter voidage
no direct passage from the top to the bottom- like a maze
what has happened with a filter voidage if there’s an accumulation above the filter? what does this indicate?
the voidage is full
filter capacity
pore size of a depth filter
no fixed pore size
mechanism of retention in depth filters?
intertial impaction- where the particles collides with the matrix and gets retained
TF: depth filters have a high retentive capacity.
true
depth filters are ____ expensive than screen filters
less
can depth filters guarantee sterility
no
pore size of screen filters?
measured in?
uniform poor size- highly engineered
measured in microns
mechanism of retention with screen filters?
direct interception
TF: screen filters aren’t easily blocked
false
why are screen filters fragile
they’re brittle
screen filters cost ___ times more than depth
5
is sterility guaranteed with screen filters? why?
yes
0.22um
smallest known bacteria is 0.4um
how are filtered validated?
bubble test
challenge filter test
direct proportion between the amount of pressure applied by the bubbles and the….
porosity of the filter
explain the bubble test
put their filter into an apparatus, from the underside they put gas, then increase the amount of pressure till bubbles come up in a steadily
• Direct proportion between amount of pressure applied and the porosity of the filter
explain the challenge filter test?
challenge the filter with the smallest bacteria and see if it filters it out Brevundimonas diminuta (0.4um)
what is the smallest bacteria?
Brevundimonas diminuta (0.4um)
how does moist heat cause death?
Death by protein coaggulation and hydrolysis more rapid
what types of products is moist heat used for?
aqueous products / devices/ dressings
how does dry heat cause death?
Death by oxidative processes- lot longer
what types of products is dry heat used for?
dry powders / oil preparations / glassware and instruments
technology for dry heat sterilisation?
dry heat ovens
sterilising tunnels
what is a dry heat oven. used for _____ heating
essentially like a domestic oven- tend to be for more batch heating
what is a sterilising tunnel? is a _____ process
continuous process- product slowly moves through dry heat
3 mechanism of heat transfer
conduction
radiation
convection
if the loading pattern is correct what should we get
good air circulation
dry heat cycle?
drying
heating
exposure
cooling
what’s the longest part of the dry heat cycle? how long does it take?
cooling
16 hours
what type of steam do we want for autoclaving?
dry saturated NOT wet or superheated steam
will wet steam sterilise the product
yes but decrease the quality
superheated steam has a lower ______ content. will kill by….
moisture
oxidative kill not hydrolytic
what is the issue with superheating steam killing by oxidation?
much slower process, so will take longer
in autoclaving what should the temperature be maintained within
+-5 kelvin of the limit
autoclaving time of contact must be sufficient enough to give what?
SAL
