Special Projects 1 Enlightening Chemistry Dyes Lab and Thin Layer Chromatography Crime Lab Introduction The goal of the crime lab is to make use of ink analysis in order to match the ink from an unknown pen to that of a known pen The goal of the luminescence lab is to utilize different techniques to make objects light up in a specified way This shows how chemical light can be produced in various ways This lab highlights three separate methods of creating chemical light Those are phosphorescence fluorescence and chemiluminescence Each of the chemical light systems has a source of energy as well as an organic molecule that receives light and then emits that energy as light When a photon hits an electron in a nonbonding orbital it excites it so that it bounces up to the anti bonding level When the electron comes back down it releases energy in the form of light This transmitted light is what the human eye sees if it is on the visible spectrum The energy gap of the bonding and nonbonding molecules in a certain molecule directly relates to a wavelength of light that can be absorbed The crime lab was centered on solving an investigation You were given an anonymous note and several possible suspects pens Through the use of multiple techniques you hope to identify who wrote the note Ink extraction is a method used in this lab Methanol is painted onto the notes in a test tube and the test tubes are placed in hot water Boiling extracts the ink because it causes ink to leach off paper and into the methanol solution Another technique that is used is analysis through the use of a UV Vis spectrophotometer The UV Vis spec emits light through a sample and records the amount of each wavelength that is transmitted It then calculates the absorbance values from the transmittance values and graphically displays this information The graph that it displays is an absorbance vs wavelength graph The highest point on the graph is considered the maximum wavelength or lambda max for that given samples In a research case in China a test was run in which 33 blue inks were examined through UV Vis data analysis Using the absorbance values of the inks after being dissolved in DMF as variables in principle component analysis they were able to determine that the reliability of the three components was greater that 86 The results were then verified through the use of thin layer chromatography 1 This is one instance that clearly displays that UV Vis and thin layer chromatography are comparable methods in this type of analysis Another way to separate compounds is through the use of thin layer chromatography TLC Using silica or alumina a plastic or glass plate is coated in a thin layer Because both silica or alumina are polar other polar materials will adhere to the plate In TLC a drop of ink dotted onto bottom of the plate The plate is then placed in a chamber containing a solvent The solvent then runs up the plate carrying the carrying the compound mixture with it Every component in the mixture has a different polarity as a result each component has a different adherence to the plate The different solvents containing ink then run toward the top of the plate which results in the separation of the components of the solvent because of the different polarities of the components Every ink has an Rf factor The Rf factor is a ratio of the distance a compound traveled to the distance the rest of solvent traveled It is in effect a way to determine different compounds are located on the plate relative to each other 1 Guo Ruihua Jiali Su Hong Zou and Kelin Liu Characterization of Blue Gel Pen Inks Using Principal Component Analysis of Ultraviolet visible Absorption Spectra Journal of Modern Instruments 2 2011 49 51 Procedure Dyes Half Phosphorescence 1 Squirted polyaromatic acids onto two pieces of filter paper over a sink 2 Placed filter paper on hot place on low for 5 15 minutes until bone dry 3 Placed filter paper unter UV lamp Long and Short UV radiation Note do not look directly into the lamp This can cause damage to eyes 4 Observed color under UV lamp 5 Turned off lamp 6 Observed the color intensity and duration of glow Fluorescence 7 Observed beaker of tonic water under UV lamp from the top Described intensity and color of the glow 8 Observed what happened when the lamp was turned off 9 Placed large beaker of water under lamp 10 Observed Nothing happens 11 Added 1 to 3 drops of the concentrated fluorescein solution 12 Shone UV lamp on the solution 13 Observed with UV lamp on and off 14 Added a drop of fluorescein to the beaker of tonic water and observed 15 Placed a chromatography plate containing fluorescent indicating dye under UV lamp 16 Recorded how fluorescence differed from phosphorescence base on previous observations Chemiluminescence 17 Flushed an Erlenmeyer flask with nitrogen by placing the hose from a nitrogen tank in the bottom of the flask for 30 seconds 18 Removed hose quickly 19 Added 2 mL of TKDE Tetrakis dimethylaminoethylene 20 Coated the bottom of the flask with LiCl 21 Stoppered the flask immediately 22 Observed 23 Removed stopped then restoped 24 Swirled 25 Observed 26 Mixed 5mL of Luminol in DMSO with 5 mL of dye in a scintillation vial 27 Repeated step 10 with Fluorescein Rhodamine B Rubrene Perylene and once with no dye 28 Added 1 mL of 1 0M NaOH 29 Covered and shook 30 Observed colors 31 Mixed 4 grams of Al2O3 and 4 mL 2 H2O2 in an Erlenmeyer flask 32 Added 25 mL of one of the dyes Perylene Tetracene 2 3 benzanthracene 9 10Dipehenylanthracene or Rubrene 33 Added 2 mL of oxalyl chloride in the CH2Cl2 solution with a pipette 34 Swirled and observed Crime Half Ink Extraction 1 Put together water bath at bench and heated to 65oC 2 Cut notes into small strips and placed into a marked test tube 3 Added 2 mL of methanol to each test tube 4 Heated test tubes using hot water bath 65oC until the methanol boiled for 5 minutes Note methanol is flammable 5 Allowed test tubes to cool to room temperature 6 Used Aspirator 7 Observe the colors of the solutions the differences between them 8 Analyzed whether or not if who wrote the note could be identified at this point UV Vis Spectrophotometry 9 Blanked the UV Vis with methanol 10 Poured each of the test tubes into separate cuvettes filling the cuvettes to the marked line 11 Recorded a spectrum 12 Printed a spectrum 13 Placed 10 mL of methanol containing the ink into another marked test tube 14 Compared each of the spectra taken 15 Tried to identify the red