Experimental plan for lab - Essay Example

of the s 2 February Experimental Plan for Lab Experiment Determination of chemical composition of latent fingerprints by Gas Chromatography-Mass Spectrometry (GC-MS)Objectives of the experimental planTo carryout extraction of fingerprint residues and prepare the components for GC-MS analysisTo derivatise polar compound and make them amenable for GC-MS analysisTo determine identification of compounds present in the residues based on fingerprint analysis by GC-MSTo use GC analysis data and carryout library search to identify name and quantities of the compounds identified from the analysis of ridge patterns of fingerprints to identify crime scene criminalsPrinciple of the experimentPolar compound will be extracted from the fingerprint residues and derivatised to make them volatile.

Volatile compounds will be converted into gas and trapped by the ionizing flame to capture and transfer them onto the recorder that records mass and charge ratio (m/z).Short description / introductionPrevious methods of crime suspect’s identification using DNA analysis and comparison of existing data from the integrated automated fingerprint identification system are not exhaustive because such information depends on their authenticity from the time of collection from the crime scene. Besides, identification of trace elements and clues in crime scene is a major challenge in the forensic science.

Therefore, some of the commonest methods are less accurate and time consuming with low levels of reliability making it difficult to identify the specific culprits especially nowadays that criminals are very knowledgeable. However, according to Hartzell (689) invention of chemical processes like GCMS, which uses trace materials from the crime scene is revolutionising the path taken by forensic scientist and criminal investigators because of its reliability, accuracy and the ability to identify signature molecules even at trace and minute levels.

Experimental design Fingerprint residues will be collected on glass slides or glass beads This will be followed by extraction of the chemical constituents from these residues using chloroformThen conversion of fatty acids and other components into trimethylsilyl derivatives to make them less polar and thermal stableAnd finally carrying out an MS library search for the identification of components present in the fingerprint and matching them with existing information from the databasesProcedure of the experiment 1.

Equipment A GC-MS model Hewlett Packard G1800C GCD system (Palo Alto, CA0 will be used, this model has the following specifications fitted with a quadrupole mass spectrometer ZB-5 column (30m X0.25 mm, Phenomenex, Torrance, CA)Detector and injection port – 280oCHelium as the carrier gasFlow rate 1 mL/minInjection volume 1mL (splitless modeInitial temperature of the column set at 50oC for a duration of 1 minTemperature ramp at 10oC/min , a final temperature of 310oC will be held for 20min2.

Chemical MaterialsChloroformEthyl acetateBis (trimethylsilyl)trifluoro-acetamide –BSTFA (AR, Sigma)Small glass beadsMicroscope slideCotton swabs4 ml vialsTeflon-lined caps3. Extraction ProcedureProcess utilising two fingerprint collection will be used according to Brittany et al., (689)Appropriate gloves will be worn before commencement of the experimentGlass beads will be washed with chloroform before sample collection 5 clean beads placed in a 4mL vialVolunteers will provide the samples by rubbing their fingers across the forehead before using the clean beads from the vials in rubbing between their fingerprints for 15 seconds and then immediately placing the beads in the vialThen 400ml of chloroform will be added to the vial to begin the extraction process.

The second sampling procedure will involve taking a latent print from the surface like a microscope slide that was cleaned using chloroform. Samples will be obtained in the same method with a few modifications that involves instructing volunteers to press their thumbs on the slides for similar duration. Removal of print done using a cotton swab soaked in the chloroform, the end of this swab is cut with a clean scissors and placed in a 4 mL vialThen 2 mL of the extraction solution is added for the extraction of fingerprint residues4.

Sample preparation for GC-MS analysisAfter the above procedures the vials are capped, vortex mixed and left to stand at room temperature for 30 minutesRemoval of the extract from the beads using a disposal clean glass pipette into a new vial (4mL capacity)Evaporation of the contents to dryness using streams of nitrogenReconstitution of the extract with 25 units of ethyl acetate before carrying out derivatisation with 25 volume N,N-bis(trimethylsilyl)trifluoroacetamide (BSTFA)Blowing nitrogen over the solution, capping of the vial, and mixing of the solutionHeating the sample at 90oC for 30 minutesAnalysis by GC-MSControls samples involved using glass beads and glass slides that did not have deposits of fingerprints Expected results (observations)a.

Chromatograms representing fingerprint samplesb. Evaluation of quantities of residues obtained by different methods (glass bead method vis-a-vis )c. Evaluation based on the abundance levels of total ion chromatogramsd. Peak identification based on how they match with those from the NIST library of mass spectrae. Identifying specific components with the high peak size as the most abundant compound and list other compounds in their order of abundancef. Comparing how these compound differ amongst the different individual volunteers g.

Assessing any significance difference of compound from different gender (male and female) as well as signature compounds associated with certain habits like smoking, cosmetics, etc.ConclusionI. The experiment aimed to help appreciate derivatisation of polar compounds amenable for GC-MS analysisII. Gaining fast hand knowledge on gas chromatography and mass spectrometryIII. Improving analytical skills and judgement skills based on forensic materials Work citedHartzell-Baguley, Brittany, Rachael E .

Hipp, Neal R. Morgan, and Stephen L. Morgan. "Chemical Composition of Latent Fingerprints by Gas Chromatography–Mass Spectrometry an Experiment for an Instrumental Analysis Course,." Journal of Chemical Education 48.4 (2007): 689-91. Print.