Ionising radiation as a sterilising agent Flashcards
what is radiation
radiation is energy travelling through space
- some forms of radiation are ionising
what are the 2 main types of radiation
electromagnetic and particulate
give examples of electromagnetic radiation
gamma rays, X rays, UV, infrared, visible light
give examples of particulate radiation
a-particles, B-particles (high speed electrons), neutrons, protons
What is meant by ionising
can add or remove electrons from molecules, producing electrically charged ions
what are the types of waves on the electromagnetic spectrum
- radio
- microwave
- IR
- visible
- ultraviolet
- X ray
- gamma rays
name the different units of radiation
- activity of a source
- absorbed dose
- energy of radiation
what are the units of activity of a source
Becquerel (bq)
- 1 bq= 1 nuclear disintegration per second
what are the units of absorbed dose
Gray (Gy)
- 1 Gy= the absorption of 1 Joule of energy per Kg of material
what are the units of energy of radiation
electron volts (eV) or millions of electron volts (MeV)
describe the characteristics of gamma rays in ionising radiation
- short wavelength, ionising, high energy and highly penetrating
- usually 60Co source
- gamma rays bombard the materials which results in emission of lower energy photons and electrons
- items pass in a zig zag pattern around the source
- exposure time is long
- standard reference dose is 25Gy
- specialised process with high safety control
what occurs in the generation of gamma ray radiation
Cobalt source emits 2 photons and one electron
list the organisms from least sensitive to most sensitive to ionising radiation
- prions
- viruses
- bacterial spores
- yeast and fungi
- vegetative bacteria (gram - most sensitive)
how can ionising radiation have a lethal affect
- direct hits- direct alterations to the target, usually DNA
- indirect effects- free radical and peroxide formation
what are the applications of gamma radiation
- thermolabile products
- single use technologies
- disposable syringes
- range of plastics
- lab ware and culture media
- IV and infusion sets
- adhesives and dressings
- prostheses
- unit dose ointments
- dry pharmaceutical products
- metal instruments
what are the advantages of gamma radiation
- high penetrability
- cold process
- not dependent on humidity, temperature, pressure or vacuum
- does not generate residuals
- does not generate radioactivity
what are the disadvantages of gamma radiation
- specialised facilities/training
- high costs
- safety considerations- risk to operator
- deleterious effects on products
- no inactivation of endotoxin
what are the deleterious effects on plastics
- cross linking
- chain scission
-odour formation - discolouration
- embrittlement
- stiffening
- softening
- enhanced or reduced chemical resistance
- increased or decreased melting point
what are the deleterious effects of pharmaceutical products
may undergo alteration or degradation
what are the deleterious effects of aqueous environments
damage through radiolysis of water
what products may be affected by deleterious effects
plastics, glass, pharmaceutical products and aqueous environments
what do accelerated electrons (particulate) produce
high energy electron beam generated by accelerated electrons from a hot filament through an evacuated tube under high potential difference
- various machines produce electrons with energy of 5-10MeV
What are the advantages of accelerated electrons
- rapid dose delivery, therefore shorter process times than for gamma rays
- direct ionisation of molecules
what are the disadvantages of accelerated electrons
less penetrating than gamma rays
describe the properties of ultra violet radiation
- non ionising
- less lethal and damaging than ionising radiation
- causes excitation not ionisation
- induces linkages between adjacent pyrimidine bases
- dimer formation (usually thymine)
list in order from least resistant to most resistant to the microbicidal action of UV radiation
- vegetative bacteria
- yeasts
- viruses
- bacterial spores
- mould spores
- prions
what are the applications of UV radiation
- poor penetrating power, not practical for pharmaceutical/medical products
- application as a disinfection agent
- air
- work areas and surfaces
- manufacturing grade water
- microbiological safety cabinets
what is gamma radiation
A terminal sterilisation process allowing for parametric release
