ATP testing has become the standard method for determining the amount of organic residue on food production surfaces after cleaning for sanitation verification. Each ATP testing system uses a chemiluminescent reaction to produce light that is directly proportional to the amount of ATP in the sample. The light is measured by a device called a luminometer that typically uses either a photodiode (PD) or a photomultiplier tube (PMT) light sensor.
There are a number of ATP testing systems on the market and the industry debates the advantages and disadvantages of each sensor, particularly the sensitivity. Claims have been made about the sensitivity of the two sensor technologies that require clarification in the context of ATP testing and sanitation verification.
Light Sensor Technology
Silicon photodiodes (SiPD) are the newest generation of PD that directly convert light into an electric signal without amplification. PD offer a number of advantages that make them practical for a range of applications. They are small, lightweight, robust and easy to customize. Moreover, PD have reproducible sensitivity due to low background noise and low signal degradation (drift) over time. Neogen’s AccuPoint® Advanced ATP testing system uses a silicon photodiode to accurately and consistently detect low light emissions.
Photomultiplier tubes have been used for decades in a variety of scientific applications. PMT use the photoelectric effect to convert light into an electrical signal and amplification to strengthen the signal. PMT can detect an individual light unit providing ultimate sensitivity; however, PMT are fragile and somewhat unreliable due to high background noise from amplification, high drift, and sensitivity to external magnetic fields and temperature.
(Table above is material from EG&G Optoelectronics.)
Are ATP testing systems that use photomultiplier tubes more sensitive than systems that use photodiodes?
Not necessarily, while PMT can technically detect lower levels of light than PD, the sensitivity of the sensor is only one aspect of the sensitivity of the system. Neither sensor offers significant advantages over the other within an ATP testing system. Sampler design and chemistry are additional components that affect the sensitivity of an ATP testing system. For more information about Neogen’s AccuPoint Advanced’s exceptional recovery in real-world situations, check out NSF’s independent study comparing the top five ATP testing systems for accuracy and consistency.
In addition, AccuPoint Advanced chemistry is optimized for liquid reagent stability and light output with a more consistent reaction over the detection time. The chemistry is balanced to produce detectable light at low levels of ATP, increasing the system’s sensitivity.
Photodiodes and photomultiplier tubes offer similar performance in sensitivity; however, photodiodes are often a more rugged option. Optimal sensor technology combined with advanced sample recovery and precise chemistry will make all the difference in your sanitation verification program. The sum of the parts are designed to provide you the data you need to make informed decisions and help protect your brand.