The forensic use of Chemiluminescence and Luminol

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Graduation project by Henk Nieweg:The forensic use of Chemiluminescence and Luminol, or, how to deceive Gilbert Grissom

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Chemiluminescencee forensic use of chemiluminescence and luminol How to deceive Gilbert Grissom

H. Nieweg1

Table of contents1 Introduction 1.1 On forensic science . 1.2 On chemiluminescence . . . . . . . . . . . . . . . 4 6 2 On luminol 2.1 Reaction mechanism . . . . 2.2 Reaction with catalyst substance. . . 2.3 Other reactions with luminol . . . 2.4 Forensic use of chemiluminescence and luminol . 2.5 Boundaries of luminol . . . . Research questions and hypotheses 3.1 Research questions . . 3.2 Hypotheses . . . 3.2.1 Hypotheses to experiment 1 3.2.1 Hypotheses to experiment 2 3.2.1 Hypotheses to experiment 3 Materials and methods 4.1 Materials . . . 4.2 Preparation . . . 4.2.1 Spray A, the luminol spray 4.2.2 Spray B or C, the soda spray 4.2.3 Copper sulfate solution . 4.3 Methods . . . Results 5.1 Results of individual tests 5.1.1 Experiment one. 5.1.2 Experiment two 5.1.3 Experiment one. . . . . . . . . . . . . . . . . . . . . 7 8 8 9 9

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Analysis and conclusions 6.1 Conclusions of each individual test . 6.1.1 Conclusions of experiment one . 6.1.2 Conclusions of experiment two . 6.1.3 Conclusions of experiment three 6.2 Conclusion . . . .

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Discussion 7.1 Documentation headaches . . . 7.1.1 Vernier setup one . . . 7.1.2 High-speed camera . . . 7.1.3 e Free University and Vernier setup two Sources and acknowledgements 8.1 Sources of information . 8.2 Acknowledgements .

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Appendix First article published on the use of luminol in a forensic manner: Die chemiluminescenz des Hamins, en Hilfsmittel zur Aundung und Erkennung forensisch wichtiger Blutspuren. Dr. W. Specht2

A bullet runs through it, part 2CSI: Crime Scene Investigation [At a community meeting, in a church] Grissom: Hello. My name is Doctor Gil Grissom. I'm the night shi supervisor of the Las Vegas Police Department's crime lab. I'm not a police ocer, I'm a scientist. Shooter's brother (interrupting): You work for the cops, that makes you a cop. You're not on our side. Grissom: Actually I'm a forensics expert. My job is to collect physical evidence from a crime scene to determine who did what to whom and how did they do it. I've been asked to come here today by the Mayor and Sheri Berdic to present our analysis of the evidence in this case to your community. Shooter's mom: Why here? Why should we believe your evidence? Grissom: Physical evidence cannot be wrong, it doesn't lie. It's not in uenced by emotion or prejudice, it's not confused by the excitement of the moment. I'm here [(looks up)] in God's house to explain to you the truth about exactly what happened the other day.

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1.1

On forensic science

Forensic Science, or forensics, is the combination of a number of sciences in order to serve the legal system. e term and idea behind forensics has existed since Roman times. Our word forensics was derived from the Latin forensis, which meant as much as before the forum. Back then the two parties of a con ict, the accuser and the accused, had to present their case in front of the forum. e individual with the best presentation usually, the best forensic skill, would win the case. is practice is still visible in modern day courtrooms and the reason some individuals feel the need to hire high priced advocates. While in America almost every self-respecting police force has a Crime Scene Investigation unit, the Netherlands has its own national forensic unit in the Dutch Forensic Institute (DFI). Here scientists work on, for example, DNA analysis of crime scenes, but also travel the country to process scenes on location. e DFI does exactly what the ctional character of Gilbert Grissom said in the quote on the previous page. It collects physical evidence to support the police in investigating crimes, and, to determine who did what to whom and how they did it. e DFI isnt only investigating crimes, scientists are also busy investigating new techniques and equipment to advance the eld of forensic science. Additionally, the DFI is part of the ENFSI, a large european network of forensic laboratories. is network was founded in 1995 and is now a group of over 50 forensic centers in 30 countries. One of the main goals of the ENFSI is improving the quality of forensic research worldwide. e most prominent activity of the ENFSI is the exchange is standardization of forensic practices. In 16 workgroups, divided in areas of expertise, researchers exchange knowledge and experience and write Best practice manuals. In addition to this these groups routinely organize conferences and workshops.

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chemistry |kemstr| (abbr.: chem.)noun ( pl. -tries) Chemistry is the branch of science that deals with the identi cation of the substances of which matter is composed; the investigation of their properties and the ways in which they interact, combine, and change; and the use of these processes to form new substances.

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1.2

On chemiluminescence

Chemistry is the study of the interaction between substances, the processes and new substances formed. Most of the interactions we study take place in test-tubes and laboratories, with people in white coats looking at glasswork and computer screens. However, such interactions also happen all around us. Even in our bodies chemistry is ever present. A large number of these reactions only cause changes to the substances involved. If one adds enough of A to a sucient amount of B, then C is created right before your eyes. It gets more interesting when energy becomes a factor in this process and A and B result in not only the creation of Cs new atoms, but also the vibration of Cs atoms. e vibration is caused by energy released in the reaction. Because these molecules vibrate, they release their energy in the form of heat. When all the energy is burned, the molecules stop vibrating and the substance will eventually cool down. It is even more interesting when the molecules do not release their chemical energy in the form of heat, but in the form of light instead. is is where chemiluminescence occurs. In the reaction, a molecule is excited and slowly returns to a ground state while releasing light or, in its turn, exciting a second particle that can produce light. e best example of chemiluminescence in every day life can be found in glow sticks. ese plastic sticks contain a chemical, which is usually hydrogen peroxide, and a small vial containing a second chemical, which is in most cases an ester. e stick will glow when the vial is broken and the components are released. We have all seen this eect during school parties where the DJ will throw glowing sticks into the audience. e various colors seen in gure 1 can be attributed to the uorescent dye used. Chemiluminescence is not only used in test tubes and during dance events, it is also used by re ies. e male re y uses adenosine triphosphate (ATP) in reaction with a luciferin substrate and the enzyme luciferase to create an illumination utilized for attracting a mate. is is referred to as bioluminescence. One of the most interesting phenomena in chemiluminsence and bioluminescence is a luminol hydrogen reaction. Here, 5-amino-2,3dihydro-1,4-phthalazinedione reacts with hydrogen and produces, amongst other products, energy in the form of light. However, the reaction of the compounds is so limited that the amount of light produced is almost negligible and the total reaction can take up to 24 hours. is makes the of luminol with hydrogen unusable for most purposes, including glow sticks. e reaction is speeded up considerably when a catalyst is added to the Figure 1.1 compound. is catalyst can, for example, be iron ions (Fe2+ / Fe3+) or the copper ion Cu2+. e reaction will speed up dramatically if you add any of these catalysts. e 24 hour reaction time will be shortened to a few minutes or even a few seconds. During this short and reasonably aggressive reaction, a relatively large quantity of light will be produced, enough to be easily visible by human eyes. is helps in making luminol more useable for other purposes, but still makes it dicult to use a reaction of luminol with hydrogen in glow sticks. ese luminol and hydrogen sticks would only light up for a few minutes, at best!

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Chapter 2

On luminol2.1 Reaction mechanismA reaction of luminol with hydrogen peroxide happens as seen in gure 2.1, or more detailed in gure 2.2.

Figure 2.1

Figure 2.2 Luminol reacts with the hydrogen peroxide producing energy and 3-aminophthalate. A commonly assumed mechanism of this reaction is described below and clearly visible in gure 2.2. - Strong base removes nitrogen protons leaving a negative charge - Oxygen creates a cyclic addition to the carbonyl carbons - Nitrogen gas and energy are released by the reaction7

A speci c feature of luminol is its chemiluminescency, resulting in the energy being generated in the form of light instead of heat. is reaction occurs at such a slow pace that it is barely detectable under normal circumstances, and this light is invisible to the human eye in most environments. When luminol and hydrogen react in a setting as above, the reaction can last from 24 hours up

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