This document provides a list of Do’s and Don’ts that will assist the systemSURE user to make the right interpretations and avoid common mistakes.
The systemSURE is a photodiode based reader for Hygiene Monitoring of surfaces and rinse waters. Although relying on different detection electronics, the sensitivity of the system in combination with the Ultrasnap device is down to around 2 femtomol, which is as good as many of our competitors. The instrument background noise is much lower than other units, which means that a result of 10 RLU already indicates the presence of ATP in the sample! The lower numbers do not mean that the system is less sensitive!
- Make sure the swabs are at room temperature when activating them.
The enzyme in the test work optimal at room temperature (18-30 C). Lower or higher temperatures during measurement will result in false negative readings. The sampling can be done at various temperatures, as long as the activation (snapping the valve with the enzyme) is done at room temperature.
- Do not expose the swabs to strong sunlight or very close to TL-lamps.
The liquid stable enzyme in the snap valve is sensitive to these light sources and the activity can become less. Keep the swabs in the pouch provided when you don’t need them.
- Take realistic sampling points and apply good contact during sampling.
Try to swab an area of 5 x 5 cm. Make sure that the pressure during swabbing is good enough to pick up traces of food residues and bacteria. Do not sample areas that you would not sample with your reference method either.
- When snapping and squeezing the valve, make sure all the liquid flows down to the bottom of the swab tube.
For correct results, it is important that all the liquid is down in the tube. Check if the bulb is empty and shake the swab for a few seconds before putting it into the instrument. The air bubbles in the sample do not influence the test.
SystemSURE II instrument
- Set and store the cut-off limits for the different surface types
The instrument can store up to 99 different combinations cut-off limits thresholds (PROG 1-99). The table below shows typical cut-off values for different surface types and rinse water. These are guidelines that may need adjusting to customer specific situations.
Recommended RLU threshold values depend on the surface that is being sampled:
|Control Ultrasnap||< 5||6-10||>10|
- Do not hold the instrument horizontal or upside down during measurement
The light sensor of the instrument is located at the bottom. To make sure that all light is measured, the sample liquid in the swab must be at the bottom as well. Therefore it is important that the instrument is steady and upright during measurement. Just hold it in your hand until the result is displayed.
- Do not expect a 100% correlation between ATP and traditional Plate Count
Good cleaning removes all product residues. The ATP test is a ‘dirt’ test, not a ‘bug’ test. ATP will detect traces of product left on the surface after cleaning. It will also detect bacteria, but product residues are the most important source of ATP. Bacteria can only grow in presence of product. If product residues are properly removed, bacteria will get no chance to develop.
There is about 80% agreement between ATP and the traditional Plate Count method. In about 20% the ATP test will be positive and the traditional method negative.
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