of the chemiluminescent image is seen below the two images . The left-hand side of the histogram is showing the shadow detail and the right-hand side shows the highlights . The software also provides the mean , median , standard deviation , the total amount of pixels in the image , the pixels in a range and highlight clipping . The mean , median and the standard deviation are the measure of brightness in image . Clipping refers to the loss of detail when a certain part of the histogram is touching either side . This can be solved by altering exposure settings .
Chemiluminescence was detected on all the 60 blood-stained samples . The blood-stained polyester samples , throughout all conditions , had brighter chemiluminescence than the cotton swatches regardless of the detergent used . The corresponding pixels for the polyester swatch had the highest pixels in the preliminary condition ; 32.2 % for the swatch washed with non-biological laundry detergent and 29.1 % for the biological detergent . Polyester swatches washed with the biological laundry detergent continued to have the highest pixel percentage in all conditions , but this reduced by the third condition . For example , the average pixel value in experiment 1 was 28.8 %, 12.4 % in experiment 2 and 7.2 % in experiment 3 . A similar pattern was also noticed in polyester swatches that were washed with the non-biological laundry detergent where the values of 27.2 % in experiment 1 , 8.5 % for experiment 2 and 6.4 % for experiment 3 were gathered .
In the preliminary condition , cotton swatches had values of 16.3 % for the biological and 11.1 % for the non-biological detergent . Much like the polyester samples , the pixel values decreased throughout the experiments as the washing number increased . For example , the cotton biological swatch had a value of 7.8 % in experiment 1 , 5.0 % in experiment 2 , and 5.2 % in experiment 3 . The non-biological detergent cotton swatches gave values of 11.1 % in the preliminary , 11.4 % in experiment 1 , 5.3 % in experiment 2 and 4.0 % in experiment 3 .
Cotton swatches washed with both the biological and non-biological capsules showed discrepancies in the chemiluminescence intensity . For example , the cotton non-biological detergent had values of 3.9 %, 15.5 % and 15.0 % in swatches 1 , 2 and 3 . This could also be seen in the swatches washed with biological capsule where values were 5.7 %, 13.3 % and 4.5 % respectively . This discrepancy is a result of human error when handling the swatches during the drying and imaging period .
Chemiluminescence was also detected in some of the control samples though these were less than 0.001 % for most apart from the cotton controls for the biological detergent in the preliminary test where the value was 0.11 %. Chemiluminescence was also noted on the tiles during the preliminary testing . Figure 6 is one such example where chemiluminescence was detected on both the background tile and the bloodied swatch . One of the tiles was then imaged on its own ( Figure 7 ) and chemiluminescence was noted ( pixel value of 0.2 %) though not as significantly high as the swatches . The tile was not cleaned prior to imaging so it is likely that a catalyst was already present that produced a false negative with luminol . To combat this , tissues were placed on the tiles prior to spraying and imaging . The tissues were changed repeatedly to further prevent background chemiluminescence . Charts 1 to 4 in the appendix show the results for each condition more clearly .
The use of biological and non-biological laundry capsules was to see which performed the best at cleaning stains . Biological detergents contain enzymes to break down common clothing stains such as food and dirt ( Persil , 2020 ). Non- biological detergents , on the other hand , do not contain enzymes ( Persil , 2020 ). Both capsules had similar chemiluminescence intensity but the biological one worked better .
Discussion
Overall , chemiluminescence was detected on all 60 samples where blood was added . Luminol can react with even the smallest of traces so it was expected that it would detect blood from swatches that have been washed three times . The controls showed miniscule amounts of chemiluminescence when it should not have . Instead , it is likely that the luminol reacted with an unknown catalyst that was possibly present in the washing machines or the airer . The laundrettes are used daily by some 400 or so students who live in that accommodation and are only prewashed every so often . As a result , it is possible
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