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Measurement of antiviral activity on plastics and other non-porous surfaces; ISO 21702:2019

ISO 21702:2019 is the test standard for antiviral activity on plastics and other non-porous surfaces. The test evaluates the decrease in infectious virus following contact with a specific surface for a designated length of time. This test can be used with enveloped and non-enveloped viruses and is carried out under specific safety containment conditions classified for each specific virus.

Following a set time of viral contact with the test surface, viral infectivity is assessed using virus specific, commercially generated, cell lines to determine resulting viral infectivity. Recovered test virus is incubated with susceptible cells in a plaque assay at 37°C ± 1°C in a CO2 incubator.

The infectivity titre of virus is calculated based on the test parameters and then this data is used to calculate the antiviral activity (R).

R = (Ut – U0) – At – U0) = Ut – At

Where

R is antiviral activity;
U0 is the average number of plaques recovered from control test surfaces immediately after inoculation, in PFU/cm2 (representing the starting amount of virus);
Ut is the average number of plaques recovered from untreated test surfaces after X test hours, in PFU/cm2 (representing the control for the testing time-point);
At is the average number of plaques recovered from treated test surfaces after X test hours, in PFU/cm2 (representing the surface test for the testing time-point).

Measurement of antibacterial activity on plastics and other non-porous surfaces; ISO 22196:2011

ISO 22196:2011 is the test standard for antibacterial activity on plastics and other non-porous surfaces. The test evaluates the decrease in infectious bacteria following contact with a specific surface for a designated length of time. This test can be used with gram-positive or gram-negative bacterial strains.

Following a set time of bacterial contact with the test surface, viable bacteria are assessed via serial dilution subculture in petri dishes at 35°C ± 1°C for 40-48 hours.

Standard bacterial strains used in this test include but are not limited to Escherichia coli (ATCC 6538P) and Staphylococcus aureus (ATCC 8739).

The number of viable bacteria is calculated based on the test parameters and then this data is used to calculate the antibacterial activity (R).

R = (Ut – U0) – At – U0) = Ut – At

Where

R is antibacterial activity;
U0 is the average number of viable bacteria, in cells/cm2, recovered from control test surfaces immediately after inoculation (representing the starting amount of bacteria);
Ut is the average number of viable bacteria, in cells/cm2, recovered from untreated test surfaces after X test hours (representing the control for the testing time-point);
At is the average number of viable bacteria, in cells/cm2, recovered from treated test surfaces after X test hours (representing the surface test for the testing time-point).

Accelerated aging technical information

Accelerated aging is an artificial procedure used for establishing the lifespan or shelf life of a product in an expedited manner so that a product can be released to market ahead of long-term testing. Data obtained from the study take into consideration environmental conditions such as temperature, humidity and vibration which simulates the effects of aging on the materials.

The primary accelerated aging standards are:

NSI/AAMI/ISO 11607-1:2019: Packaging For Terminally Sterilized Medical Devices

The guidelines given in ISO 11607-1:2019 detail the specific requirements and test methods for materials, sterile barrier systems and packaging systems to show over time their integrity and sterility is maintained until point of use.

ISO 11607–1:2019, clause 6, states that “Stability testing using accelerated aging protocols shall be regarded as sufficient evidence for claimed expiry date until data from real time aging studies are available.”

ASTM F1980-16: Accelerated Aging of Sterile Barrier Systems for Medical Devices

The guidelines given in ASTM F9180-16 detail the specific requirements and test protocols to determine the effects (if any) related to passage of time on the barrier system integrity, which may occur as a result of physical properties of the material and adhesive or cohesive bonds degrading over time and by subsequent dynamic events during shipping and handling defined in ANSI/AAMI/ISO 11607-1:2019.


Accelerated aging equation formula

Arrhenius equation = (Rate of a chemical reaction)

Universal Gas Constant (R) = 8.314 x 10-3 kJ mol
Frequency Factor (A) = sec -1
Activation Energy (Ea) = kJ mol-1
Absolute Temperature (T) = Kelvin
Rate constant = K

Accelerated aging is calculated based on Arrhenius’ equation which states that a 10°C increase in temperature doubles* the rate of chemical reaction (degradation) with the standard ambient temperature between 20-25°C. The following three variables are used when calculating the accelerated aging test duration which replicates real-time lifespan in months and years:

TAA = Test Temperature (°C)
TRT = Ambient (warehouse) Temperature (°C)
*Q10 = Chemical reaction Rate Factor (2)

Relative Humidity (RH) is not a factor in the Arrhenius equation and not used to evaluate material aging. However higher humidity levels are known to increase degradation.

RH conditions should be clearly defined within the testing data and a rationale provided for any increase above 25%. To calculate the required accelerated aging time the Arrhenius equation is simplified to the following equation:

(Accelerated Aging Factor) AAF = Q10 [(T AA – T RT) / 10]

Accelerated Aging Time (AAT) = Desired shelf life = RT / AAF

TAA = 120 (°C)
TRT = 23 (°C)
Q10 = 2.0
AAF = 2.09.7 = 831.75

RT = number of days = 365 days / year (e.g. 2 years = 730 days shelf life)

AAT = 730 / 831.75 = 0.9 days

Example Results Table:

Accelerated Aging Test duration (days) Real-Time Aging (years)
(60°C) (85°C) (120°C) (23°C)
28.1 5 0.4 1
56.2 10 0.9 2
84.3 14.9 1.3 3
112.3 19.9 1.8 4
140.4 24.8 2.2 5
Test parameters: Ambient Temperature: 23°C, Q10 value: 2, RH value: 25%

The graph below illustrates the inverse relationship between temperature and testing duration which is equivalent to a 2-year room temperature test.


ISO 16474-3: 2013 (new version 2021 has superseded 2013) Paints and Varnishes – Methods of exposure to laboratory light sources – Part 3: Fluorescent UV lamps

ISO 16474 consists of the following parts, which are all under the general title of Paints and Varnishes – Methods of exposure to laboratory light sources.

Part 1: General guidance
Part 2: Xenon-arc lamps
Part 3: Fluorescent UV lamps
Part 4: Open-flame carbon-arc lamps
Fluorescent UV lamp exposures for plastics are described in ISO 4892-3.

ISO 16474-3 specifically relates to coatings of paints, varnishes and similar materials (subsequently referred to simply as coatings) that are exposed to fluorescent UV lamps in various environmental conditions (temperature, humidity and/or water) in apparatus designed to reproduce the weathering effects that occur when materials are exposed in actual end-use environments to daylight or to daylight through window glass. Different types of fluorescent UV lamp may be used to meet all the requirements for testing different materials.

Fluorescent UV lamps (below 400nm) can be used to simulate the spectral irradiance of daylight in the ultraviolet (UV) region of the spectrum. Within the parameters of this test the samples can be exposed to various levels of UV radiation, heat and moisture. These can vary within the below categories:

a) Type of fluorescent lamp (spectral power distribution)

b) Irradiance level
c) Temperature during UV exposure (24 ± 5°C)
d) Relative humidity during light and dark cycles
e) Type of wetting (with demineralized or deionised water)
f) Wetting temperature and cycle
g) Timing of the UV/dark cycle

The radiant exposure is measured by expressing the exposure interval in terms of the incident radiant energy per unit area of the exposure plane in joules per square metre per nanometre [J.m-2.nm-1] for the wavelength selected (e.g. 340nm).

Exposure and test conditions must be specified within the report. The standard example of this is shown below:

Exposure Cycles:

Method A: artificial weathering
Cycle No Exposure period (hours) Lamp Type Irradiance Black-panel temperature °C Relative humidity %
1 4 h dry UVA-340 0.83 W/m2/nm at 340 nm 60 ± 3 not controlled
4 h condensation UV radiation off 50 ± 3 not controlled
2 5 h dry UVA-340 0.83 W/m2/nm at 340 nm 50 ± 3 not controlled
1 h water spray UV radiation off 25 ± 3 not controlled
Method B: daylight behind window glass
3 24 h dry (no moisture) UVB-351 0.76 W/m2/nm at 340 nm 50 ± 3 not controlled
Method C: Type 2 UVB-313 lamps
4 4 h dry UVB-313 0.71 W/m2/nm at 310 nm 60 ± 3 not controlled
4 h condensation UV lamp off 50 ± 3 not controlled
5 5 h dry UVB-313 0.71 W/m2/nm at 310 nm 50 ± 3 not controlled
1 h water spray UV lamp off 25 ± 3 not controlled

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