Gas Chromatography-Mass Spectrometry

Introduction The purpose of this lab was to introduce chemical development as a way to develop latent fingerprints and to demonstrate two of these methods: cyanoacrylate fuming and iodine fuming. These two methods are regularly used to develop latent fingerprints. Cyanoacrylate (or superglue) fuming was discovered as a way to develop prints in the late 1970s. The fumes of heated cyanoacrylate react with the bodily fluids of a fingerprint.

In quadrants 1 and 2 how the amount and constituents of the fingerprint residue on the substrate affects the fingerprint image, is determined. In quadrant 1, excess sebum and moisture is first removed from the finger tips with the help of a clean cloth. In quadrant 2, fingertip is first wiped around the nose or forehead to create excess sebum. Quadrant 3 and 4 were used to compare the details between untreated and dusted fingerprint residues.

Purpose: To use indicators to test for the presence of organic compounds in certain substances.

Lee, H. (2001). Advances in Fingerprint Technology, Second Edition, 2nd Edition. Retrieved January 26, 2015, from Vital Source: http://online.vitalsource.com/books/9781420041347

This purpose of this lab is to use gas chromatography to identify unknown compounds. In this lab, six known substances were first tested for their retention times to be used as standards when figuring out the three substances contained in a known mixture. The vernier mini gc in this experiment, just like all the other types of chromatography, have both a stationary and mobile phase. With this instrument, the stationary phase is a metal outer column and the mobile phase is the atmospheric air, which is how the vernier mini gc works. This instrument is used alongside a computer to be able to obtain the readings of the injected substances and shown as peaks on a chromatograph. The specific time it takes for a substance to exit the chromatography

By correlating the retention time of pure compounds to the retention time of the sample, the compound in the sample can be identified. As seen in Figure 1, there were 2 peaks seen in the GC graph, which indicates there were 2 compound made up in the product. Since cyclohexane was added into the product, it is safe to assume that the peaks were cyclohexane and bromocyclohexane. According to table 2, their retention times were 2.469 and 2.780mn, respectively from 1-2. The first peak was most likely to be cyclohexane since it is less polar compared to bromocyclohexane; therefore, the nonpolar compound will come out first at 2.469mn. If so, the second peak that came out second at 2.780mn was surely bromocyclohexane, the wanted product. According to both figure 1 and table 2, cyclohexane was responsible for 73.78% of the total sample used for analysis whereas bromocyclohexane only accounted for 26.22%. Even though the graph suggested the product was pure when the cyclohexane was neglected, some bumps could be seen within range of 3 to 4mn, which indicated that the product was not 100%

Quantitative annalise schemes identify chemicals based on their physical and chemical properties. A qualitative analysis, separates

Howlett, S. E. and Steiner, R. R. 2011. Validation of Thin Layer Chromatography with AccuTOF-DART™ Detection for Forensic Drug Analysis*. Forensic Sciences [e-journal] 56 (5), pp. 1261--1267. Available through: Anglia Ruskin University Library website http://libweb.anglia.ac.uk [Accessed on 11 March 2014].

Determining the identity of unknown compounds in a given solution is an important skill to have. This can be done through a series of steps including extraction, purification, and spectroscopic methods.1

Previously, the use of mass spectrometry has played an essential role in the identification of

Introduction Thin-layer chromatography, also known as TLC, is a principle that describes how various compounds travel multiple distances when placed as a thin layer on a plate. TLC is a technique that can be used to determine how many components are in a mixture. TLC can also be used to determine a specific compound in a mixture. After performing TLC, the retention factor (Rf) can be used to determine a specific compound in a mixture. The retention factor (Rf) is During TLC, there is a step called elution.

Each individual gave five right thumb prints. Another advantage of this experimental design was that these fingerprints were not collected on the same day, even for the same individual. The purpose of this was to show that amino acids within a person can vary marginally day to day, but there is a noticeable difference between men and women. Also, the prints were deposited on the exact same surfaces which ensures a controlled environment. This would allow for more accurate testing without the presence of unwanted variables. The surfaces included a door knob, a desk, a chair, a bench, and a computer. All fingerprints were removed with polyethylene film.

The ageing of a latent fingerprint correlates to the changes in the initial composition over time, caused by chemical, biological and physical factors. Changes to the initial composition over time involve processes such drying, evaporation, oxidation metabolism, polymerisation and degradation [Weyermann & Ribaux 2012]. The understanding of the ageing process and the resulting by-products and/or new compounds is critical in determining the age of a latent fingerprint. Even though the idea of determining the absolute or relative age of fingerprints has been around for some time, a limited number of studies in this area have been published [Archer et al. 2005; Popa, Potorac & Preda 2010; Weyermann et al. 2010].

By Using specific methods of compounds detection, we can match an unknown compound with a known compound because similar compounds will display similar characteristics. In this experiment, identifications of the unknown ketone was accomplished using thin layer chromatography, melting point, and NMR spectrometry. Thin layer chromatography is very quick but sensitive way of determining the components of a mixture or a specific compound from a list of knowns. This method is the one which was utilized in the

Every time somebody touches something, they leave behind a unique signature that forever links them to that object. This link is their fingerprints, which are unique to every person, for no two people have the same set, not even family members or identical twins. Palms and toes also leave prints behind, but these are far less commonly found during crime scene investigations. Therefore, fingerprints provide an identification process that is applicable to background checks, biometric security, mass disaster identification, and most importantly, crime scene investigations. Fingerprints are so differentiated because they are made up of distinct patterns of ridges and furrows on the fingers. The ridges are the “raised” portions of the prints, and the furrows are the “recessed” portions. This perceived uniqueness has led some people to falsely accept fingerprint analysis as absolute scientific fact. Although overall fingerprints are reliable, there are definitely situations where their accuracy can come into question.