The paper "Lipstick Analysis by Thin Layer Chromatography and Fourier Transform Infrared Spectroscopy" is a great example of a lab report on formal science and physical science. In this experiment, two methods are used to analyze six samples of lipsticks and then the origin of one unknown sample that has been gotten from a crime scene is identified. The two different analytical methods used in this analysis are thin-layer chromatography (TLC) which is a separation technique and attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) which is a spectroscopy technique. The two methods were then compared in this analysis of lipsticks.
(Andrasko, J., 1981) The analysis demonstrated that problems such as the issues on cost, time, and contamination can be approached in different ways. All industries that deal with the production of lipsticks must thus consider these considerations. Other factors other than the identification of the unknown sample were considered. These factors are those that regarded the methods that were used in terms of accuracy, speed, simplicity of the interpretation and ease of use. If a lipstick print is collected from the scene of the crime it can be analyzed chemically and this can aid in tracing the suspect of the crime committed. A small amount of the lipstick to be analyzed can be placed in an LCD plate and this plate placed in a solvent and as the solvent moves, it carries the chemical that has dissolved in it along with it.
Since these chemicals travel at different speeds, they will definitely separate forming observable bands. They thus travel different distances and their Retardation factor (Rf) can be calculated. The Rf is the distance traveled by the substance in question divided by the distance traveled by the solvent.
In high-performance liquid chromatography, the solvent is forced under pressure to go through. It requires a small sample size and due to the increased surface area created there is increased interaction between the molecules and the stationary phase thus giving a better separation of the components of the sample. (Barker, A.M. , 1972.), (Daldrup, T. and Michalke P., 1986) FTIR reveals information on the molecular structure of a material and its chemical bonding. It is used in the identification of unknown material which is thought to be present in a provided specimen.
When molecules are exposed to infrared rays, the infrared energies they absorb make the molecules at different characteristic frequencies, their bonds to vibrate. An infrared absorption plot can be made and the different patterns produced are analyzed, then using the information from the library, matching with the known signatures is done. (Silicon Fareast, 2005.) Aim The experiment aims at analyzing the six samples of the lipstick together with the unknown sample using the thin liquid chromatography and the ATR FT-IR methods.
This was achieved by performing both the analysis separately wherein the TLC the retardation factor of each of the lipstick was calculated and the unknown sample identified. In the ATR FT-IR, reference libraries of the known lipsticks were built and these aid in the identification of the unknown sample. TLC Method. So as to prevent contamination, gloves were worn at all times when handling TLC plates and care was taken to avoid contaminating the lipsticks with each other. A 1.5 cm line was drawn using a pencil and a ruler from the edge of the bottom of the TLC plate then a small amount of each known and unknown sample was transferred using earbuds to this line where they were evenly spaced.
The plate was then placed on the chromatography tank and allowed to develop for 30 minutes when the plate was removed and where the solvent had reached was marked. The plate was kept in a fume cupboard was then dried by a drier after which the Rf were calculated for each band. Method for ATR FT-IR Here a standard operating procedure (SOP) was followed that guided in the analysis using this method.
The SOP was followed in the running of the samples, in a library setting, saving spectra to the library, the checking of the spectra, and in the comparing of the spectra. Results. The Rf was calculated by dividing the distance moved by the lipstick sample by the distance moved by the solvent. A table showing Rf values of different bands. LS1 LS2 LS3 LS4 LS5 LS6 UNKNOWN LS Rf 0.51 0.35 0.58 0.37 0.53 0.44 0.35 Different absorption rates of the infrared were also obtained for all the known and the unknown lipstick and were compared to find out which matched the unknown lipstick from the spectra library created. Discussion The two different analytical methods were used for the analysis of the six lipsticks where the unknown lipstick was identified.
(Salvador, A., 2007.) By using the TLC method, the samples were placed on the plate and when the plate was put in a solvent which absorbs these samples, the solvent carried the molecules that did absorb to it along with it. Since the molecules move at very different speeds they each formed a different band from the rest of the samples and these bands were observable enough to let their distances to be calculated.
The distance of the solvent is also taken and then the Rf is calculated for every sample. This is then used to compare the findings thus letting one to identify the unknown sample. From the results, it is clear that the unknown lipstick compares with lipstick number two. Care had to be taken when performing the analysis using the TLC method because the solvent that was used is very toxic. The TLC tanks were not supposed to be removed from the fume cupboard so as not to be in direct contact with such toxic fumes.
(Jonathan, M., 2007) So as to increase the resolution of the TLC method, high-performance TLC is employed as it also allows for more accurate quantitation. Better separation is achieved very fast and it is relatively simple thus enabling its use in the analysis of such reaction products. The speed at which different molecules move depends on their attraction to the stationary phase and their solubility to the solvent.
This thus means that a change in the solvent will definitely give a different result from the used solvent because each has a different solubility to different solvents. The analyzed molecule is pushed up the plate by a strong solvent while a weak solvent slowly moves these molecules. (Laurence M. and Christopher, J., 2009) Manufacturers use varying ranges of different pigments to achieve the same color. This is done so as to give out a product of the required characteristics. When the analysis was done by the use of FT-IR, the samples were exposed to an energy source and the energy they absorbed made their bonds to vibrate.
The energy at which these molecules vibrate corresponds to that of the infrared region on the electromagnetic spectrum. (Demirdö ven, N., et al, 2004.) When the infrared absorption plot was made, the different patterns produced were analyzed and matched with the known signatures from the made libraries thus identifying the unknown lipstick. (Mukamel, S., 2000.) After comparing the results with the library made, the unknown lipstick was identified as lipstick number 2. The general problem with this method is that there is minimal elemental information that is given by it.
There are also restrictions on the kind of background solvent that is supposed to be used. The solvent should be transparent in the spectral region of interest. For absorption to be observed, the molecule in the sample must be active in the infrared region meaning that the net dipole moment of the molecule must be altered by a minimum of one vibration motion. Conclusion. The identification of a crime sample can be made possible through the use of the discussed analytical methods.
The two different analytical methods used in this analysis are thin-layer chromatography (TLC) which is a separation technique, where the retardation fractions are calculated for each and every sample and the results used in the identification of the unknown collected sample from the crime scene and attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) which is a spectroscopy technique where different absorbencies of the infrared energies that cause the vibration of the molecules are used to build libraries which are compared against the already known signatures in the identification of the sample in question.
(White, R., 1998.) The two methods can then be compared in this analysis of lipsticks. The analysis demonstrates that problems such as the issues on cost, time, and contamination can be approached in different ways. All industries that deal with the production of lipsticks must thus consider these considerations. Other factors other than the identification of the unknown sample can be considered. These factors are those that regard the methods that were used in terms of accuracy, speed, simplicity of the interpretation and ease of use.
If a lipstick print is collected from the scene of the crime it can be analyzed chemically and this can aid in tracing the suspect of the crime committed.