If you are receiving an unexpectedly higher result, there could be several reasons for this, including environmental factors or light leakage; here are the first areas to check:
Contaminated Pipette - Dirty pipettes can be a source of contamination. The care and maintenance of your pipettes is one of the most important routines for working in the lab. Implementing a strict monthly and annual pipette maintenance schedule could mean the difference between purchasing new, expensive equipment and relying on precise measurement instruments.
Dirty Photonmaster Luminometer - Dirty luminometers (tube chamber). Clean instrument regularly and immediately when experiencing abnormal readings with the PhotonMaster Luminometer Maintenance Kit
High background readings are usually caused by dirt and debris in the assay tube through spilled reagents or dirt and dust collecting in the chamber. You should have a PhotonMaster Luminometer Maintenance Kit on hand and complete a cleaning every 3-4 months. A linearity check should be done annually. When not in use, it is recommended that the PhotonMaster be stored in its field case to prevent any accidental damage to the unit.
Contaminated Plastic Consumables - The various plastic parts used in 2nd Generation ATP testing should be sterile and free of ATP. It is important to ensure that unused plastic parts are stored in a clean environment in the sealed package in which they were received and that when in use, the surfaces that come in contact with reagents or samples are not contaminated in any way (for example, avoid touching pipette tips on a surface). If you suspect you have received contaminated plastic parts, obtain a fresh, unused quantity and re-check background noise to confirm. Also, because of the risk of cross-contamination, these components are meant for one use only and should never be re-used. Using the consumables supplied by LuminUltra whenever possible is recommended since other similar materials may cause elevated readings or be incompatible with the PhotonMaster/pipettes.
Light Saturation - The photodetector used in the luminometer is highly light-sensitive and can become "saturated" with light if exposed to ambient light, such as in a standard laboratory. Customers should ensure the lid on the PhotonMaster remains closed as much as possible. Executing an RLU measurement with a luminometer overexposed to light may cause consistently inaccurate readings over time. In this case, one solution is to power down the luminometer and allow 4-6 hours for the photodetector assembly tube to return to normal.
Radio Frequency Interference - Many electronic devices emit radio frequencies (RF), a subset of a larger group called Electromagnetic Frequencies (EMF). Certain devices generate greater RFs than others and can artificially stimulate the luminometer electronics to emit high RLU's. These include wireless internet connections from personal computers or multi-function cellular telephones, very-high frequency (VHF) or ultra-high frequency (UHF) radios, cordless telephones, heavy equipment (motors, welding equipment), among others.
Helium Canisters - Avoid operating and storing the luminometer near Helium gas canisters. Helium gas can permanently damage the photomultiplier tube.
Static Electricity Interference- Ground yourself before conducting tests (a common way to do this is to touch a faucet), use a different brand of gloves, or move to a different location. Avoid wearing any PPE that can generate static electricity. I
Other Common Issues:
- Confirm the PhotonMaster Luminometer was at room temperature during testing. A reading with a Luminometer directly from a hot truck or stored in sunlight or during winter can cause abnormal readings. Allow the device to return to room temperature before operating
- Ensure the assay tubes and pipette tips are being stored in a clean environment
- All reagents should be kept at room temperature (along with the equipment) before taking readings with a PhotonMaster.