Where there is a concern that RLU (Relative Light Unit) results are not accurate and these lower than they should be it can raise concerns of interference of the test by residual chemicals remaining on the surface being tested.
Problems that may result in failure to rinse excess cleaning chemicals away during the final stages of a cleaning process, or where there is incorrect preparation of sanitizing chemicals so that they are in a too higher concentration can result in “ quenching “ of an RLU result. This means the reagents of an UltraSnap / SuperSnap could be damaged and the bioluminescence reaction subsequently inhibited. This results in the test being unable to produce the light needed to provide an accurate measure of ATP contamination. In most cases, this will result in a lower RLU result.
For the majority of sanitizers as long as they are prepared to the correct concentration they will have a limited impact on the UltraSnap or SuperSnap test result.
Cleaning chemicals that should be rinsed away or removed during cleaning are most likely to quench the test if remaining on the surface. As part of a cleaning procedure tests should be taken to confirm cleaning chemicals have been removed from a surface or equipment. These include tests for pH or conductivity.
The Hygiena Positive Control test provides a means to check for quenching of the UltraSnap or SuperSnap results to confirm the RLU results are accurate.
The Positive control vial contains Freeze-dried ATP.
- Take a new UltraSnap or SuperSnap test and rub the swab bud around the inside of the positive control vial until all the ATP solid has been absorbed onto the swab bud.
- Activate the swab test and then read in the Hygiena luminometer.
- Check the result falls in the specification above. This will confirm the tests and luminometer are functioning correctly. ( See Table above)
- Using a new UltraSnap or SuperSnap test take a swab of the surface where quenching is suspected.
- Follow the procedure in steps 1 and 2 above.
- Check the result. If the RLU value is below the Luminometer specification in the table above then this indicates there could be some interference caused by quenching.
- If possible rinse the surface and follow from step 4 above to check if there is any improvement and results are then within specification. This will show if there was interference prior to rinsing by any residues on the surface.
If possible where testing can be taken before sanitizer is applied then this will help reduce the risk of any quenching. Also, this will help prevent the need to reapply sanitizers if recleaning is required.
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