Instrument Introduction
The SURRC Photoluminescence Food Screening System (PPSL) is a mobile, mobile food screening system for rapid detection or screening of food or its ingredients for exposure. The detectable range includes herbs, spices and condiments, fruits and vegetables (including dehydrated vegetables), and products with shells or bone fragments such as crustaceans and meat. It is the recommended instrument in the European Union's standard method for detecting irradiated food (EN13751-2002), and it is also the most widely used method for detecting various irradiated foods and instruments.
The SURRC photoluminescence irradiation food screening system consists of a pulse excitation light source, a sample chamber, a highly sensitive signal detection probe (PMT), a patented photon counting system (UK Patent No 2291707) and a control unit. The volume is small and the operation is simple. Any chemical reagent is required. Most solid powder or small particle samples can be directly measured. Larger samples can be measured only after grinding or pulverization. Compared to the thermoluminescence method (TL), this method gives results for most samples without re-irradiation. Therefore, the method and apparatus are very popular in food testing laboratories, especially in enterprise laboratories, and are the fastest and most efficient means of controlling and identifying irradiated foods. In addition, because the instrument is small and portable, it can also be measured on site.
The patented photon counting technology greatly increases the sensitivity of the detection, making direct detection of the sample possible without the need for cumbersome and time-consuming pre-processing. The system is especially suitable for the detection of herbs, spices and condiments, as well as for the detection of fruits and vegetables, as well as products with shells or bone fragments such as crustaceans and meat. In fact, the system is also suitable for a wider range of foods.
Simply place a thin layer of sample in the Petri dish and feed it into the sample chamber. Powdered or small particle samples can be measured directly without preparation. Larger particles of the sample can be measured after grinding or pulverizing. The non-contact measurement process makes it easy to detect different types of food without worrying about cross-contamination. For simple screening without a computer, the test takes only 15 seconds, and the test results will show different color indicators. If connected to a computer, the single sample test time is typically 60 seconds. A large number of experiments have proved that for samples such as herbs and spices, the correct detection rate is more than 95%.
The main technical parameters
System background (20 ° C): Typical: 50 cps, maximum: 150 cps
Pulse switching period: 15 us
Preload count: 256 counts
Median threshold: 700 counts
Positive threshold: 5000 counts
Preset test period: 60 s
Detection rinciple
PhotoStimulated Luminescene (PSL) is a standard method for detecting irradiated foods. It is based on the principle that mineral residues, especially silicates or inorganic calcium, are very common in foods. of. These minerals accumulate energy in the charge carriers when subjected to ionizing radiation (irradiation). When stimulated by excitation light, these stored energy is released as photons to form an excitation spectrum. The PSL method does not damage the sample, so a mixture of organic and inorganic materials can be repeatedly measured. However, repeated measurements of the same sample will attenuate the PSL signal. For screening tests, the resulting signal levels are compared to two thresholds defined. Samples with signal strength above the upper threshold indicate exposure; samples with signal strength below the lower threshold indicate no irradiation; intermediate signal strength between the two thresholds indicates that the sample should be further tested or survey. The dual threshold concept provides an extremely effective screening method with a one-time correct detection rate of over 95%.
Two modes of operation are available
Simple Screening Mode - Based on the built-in threshold and time parameters, the sample can be placed in the sample chamber with a single press of the start button for 15 seconds. The screening mode does not require a computer connection. Ideal for routine rapid testing of routine samples.
Connected to a computer - When connected to a computer, software can customize measurement parameters (such as measurement time, threshold and data recording conditions, etc.), you can get a sample specific photon count, you can determine the dark count (no light stimulation The photon count rate of the sample chamber, the empty chamber count (count rate without sample to understand whether the sample chamber is contaminated), and the photomultiplier sensitivity test. It can also perform calibration PSL measurement on samples with uncertain screening results, and so on.
This method has many outstanding advantages compared to other irradiated food testing methods:
1. The sample does not need to be pretreated - most samples (powder and granules) can be measured by sampling in a Petri dish.
2. The operation is simple - only 15-60 seconds to get the results.
3. High accuracy - taking irradiated herbs and spices as an example, the accuracy of one test is above 95%.
4.A wide range of applications - the vast majority of food can be detected, is the most widely used of all methods of irradiation food detection.
5. Clean and environmentally friendly - no chemical reagents required.
6. Saving money - because no sample preparation and reagents are needed, the daily testing costs are very low.
7. Easy to carry - easy to measure on-site or shared between different laboratories.
