Understanding and addressing anomalies in ATP testing is crucial for accurate microbial quantification. Below, we break down common issues, their causes, and solutions, along with additional insights into troubleshooting repeatability, reagent handling, and calibration concerns.
Common Issues and Solutions
High RLU Values
- Cause: Contamination or residual ATP in equipment.
- Solution: Thoroughly clean equipment and ensure reagents are fresh and properly stored.
Low RLU Values
- Cause: Expired reagents or improper sample preparation.
- Solution: Check reagent expiration dates and review sample preparation protocols.
Background Interference
- Cause: Contaminated assay tubes or improper handling.
- Solution: Use new, sterile assay tubes and maintain consistent handling practices.
Inconsistent Results
- Cause: Varying sample conditions or procedural errors.
- Solution: Standardize testing environments, sampling techniques, and testing protocols.
How to Improve Repeatability in ATP Tests?
Sampling Consistency
Microorganisms are not evenly distributed in samples, leading to variability.
- Ensure consistent sampling locations, clean collection containers and proper flushing times.
- Mix samples thoroughly before testing.
- Collect and test multiple samples from the same location to assess variability.
Protocol Consistency
Variability in testing procedures can impact repeatability
- Perform three ATP analyses on the same sample per tester to evaluate repeatability (CV <15% RSD < 35% is good).
- Follow precise timing during assays and use accurate pipetting techniques.
Reagent Z Handling
Proper handling of the Reagent Z enzyme prevents variability in results
- Allow Reagent Z to reach room temperature before use.
- Store refrigerated when not in use, or frozen if Reagent Z will not be needed for several weeks. Avoid freeze-thaw cycles of Reagent Z.
- Exposure to temperatures above 30°C will cause Reagent Z to rapidly break down.
Reagents and Consumables:
Ensure reagents and plastic consumables are not contaminated.
- Avoid reusing pipette tips.
- Store all materials in sealed containers or bags when not in use.
- Add 100 µL of Reagent Z to a new assay tube and take a reading. Background readings should be less than 10 RLU. If higher, discard and replace.
Process and Operational Considerations
Changes in process or operations can affect ATP results
- Investigate potential equipment breakdown or maintenance, changes in biocide or disinfectant levels, changes in source water, or other process changes that may have impacted the biomass.
Need Help or Want to Learn More?
Our team of experts is here to assist you with your microbiological monitoring needs. Whether you have questions, need technical support, or want to learn more about LifeCheckTM ATP testing, contact LuminUltra® Support to get started.