Practical for Extraction Ion Profiles to Confirm an ILR - Research Proposal Example

FACULTY OF SCIENCE AND TECHNOLOGY ADVANCED FIRE AND EXPLOSIONS TITLE: PRACTICAL FOR EXTRACTION ION PROFILES TO CONFIRM AN ILR DATE: Table of Contents Summary of the method 3 Results and discussion 3 Conclusion 12 References 13 PRACTICAL FOR EXTRACTION ION PROFILES TO CONFIRM AN ILR Summary of the method The tins were heated at 1800C for two hours to remove any possible contamination, before cutting a length of cotton and hanging it over the studs on the sides of the tins. The paper clip was hanged in the centre of cotton in order to suspend the clip ready for the charcoal strip. The sample was then placed in the bottom of the tin and making sure that the charcoal strip was hanging in the correct place of the head space, before placing the tin in a preheated oven of 700C for 18hrs. The sample tins were taken out of the oven and left to cool for ten minutes, before removing the charcoal strip using tweezers and placing the strip in a glass vial containing 1.0 mL of pentane to desorb the charcoal strips. The charcoal strips were agitated in the pentane for 10 minutes, and the charcoal strips were then removed and parafilm the sample vial for freezing before running the samples on GC-MS (Newman, Gilbert and Lothride, 1998). Results and discussion ASTM E1618-10 provides definite procedure for the analysis of fire debris extract using mass spectrometry. GC-MS can be used in analysis of IL through extracted ion chromatography (EIC), compound identification and target compound chromatography. Hydrocarbons comprised mainly of alkane and aromatic compounds. The compounds were fragmented through mass spectrometer to produce ion chromatograms such as the one shown below for the total ion (Almirall and Furton, 2004; Daeid, 2004). In order to minimize the interference by pyrolysis, chromatogram that indicates the presence of alkane, aromatic compound, and cycloalkane, more detailed data like the one shown below is generated (De & Stroobant, 2013). This information allows the analyst to interpret the abundance and the type of compounds present in a sample, which are the main information for ILR classification (Almirall and Furton, 2004). As per the ASTM procedure, the sample was extracted through the use of passive headspace extraction procedure. It is a method used to separate ILR from the debris using adsorption on activated charcoal. This technique is easy to use and is sensitive. Although it lacks in speed, it makes up in efficiency (Almirall and Furton, 2004; De & Stroobant, 2013). The temperature was maintained at 700C to ensure that vaporization for higher boiling compound takes place, but low to prevent further thermal degradation of the debris. The compound above C18 in the sample may not be volatized and sampled in sorbent matrix. The debris like the activated charcoal contains adsorption sites. The adsorption bond produced between the debris and higher molecular weight hydrocarbons preludes volatization even at higher temperatures. This technique cannot be able to differentiate between diesel within the range of C9 to C23 and kerosene in the range of C9 and C18 (Almirall and Furton, 2004). The main advantage of the technique used here is that it is nondestructive. This means that the items can be re-extracted a number of times without losing its value. Therefore, if the extracts appear distorted, displaced or too weak, it can be re-extracted to obtain better sample representation (De & Stroobant, 2013). The sample were then analysed using GC-MS in the monitoring mode in order to reduce the matrix interferences and the data was analysed based on different standard variables. The statistical procedure was done on the chromatogram instead of using selected sections of the chromatogram in order to avoid elimination of the potential valuable variables that permits the discrimination of the simulated ILRs. The use of full chromatogram eliminates any subjective effects related to selection of a given variable in data analysis. Solvent blank was used to ensure that the extraction was not contaminated (Stauffer, Dolan& Newman, 2008). Gas chromatography is used to identify various components through the use of retention time and pattern recognition, which is a visual composition of chromatograms (Chandler, 2009). Pattern recognition requires removal of human bias, since data interpretation is carried out through visual inspection. Potential interferences vary depending on the matrix they are derived from. The chromatographic data is complicated by the change in composition due to heat exposure. Due to high interference level due to pyrolysis and low concentration of analytes, mass spectrometer extracts the analytes selectively (Chandler, 2009; De & Stroobant, 2013). GC-MS provides specific information of single components found in a sample of debris, but many GC peaks contains a mixture of two or more hydrocarbon components like as shown below for casework sample. GC can provide information about the identity of the components in a given sample using common fragmentation pathways that is unique for each substance. Mass chromatography assists in recognizing the molecular mass of those ions (Hübschmann, 2014). The retention time for each sample and their m/z ratio are shown below. Dodecone Decane 1, 2,3 tmb The peaks are used to determine if the ILR is present or absent, are known through their mass spectrum. This can be accomplished through pattern matching of the ion chromatography extraction. The extracted ion chromatography are compared with the known standard of IL or a specific compound can be identified by mass spectrum and compare them to the mass spectrum of the known standard. This process of characterization of IL is done according to the ASTM scheme (ASTM E1618-10). The following table shows the Rt for different target molecules (Daeid, 2004; Schmidt & Symes, 2008). ILR can be identified if there are significant peaks in the chromatogram which may be attributed to the sample matrix. If the peaks do not match that of the standard peaks for ignitable liquid it is regarded to be negative. Total ion count The ion mass spectrum for 1, 2, 4-trimethylbenzene, m/z = 120. 1, 2, 3-trimethylbenzene which is C3 – alkylbenzene lies right next to the C4 and C5-alkylbenzene. From the table above, the area for C5-alkylbenzenes with m/z of 148 is not very specific for the selected parent ion m/z Decane, n-dodecane, adakane12, CH3(CH2)10CH3, Dihexyl, n-Dodecane, Duodecane Quality control -This is performed to ensure the consistency of an instrument in reporting the sample results. It is done in the lab following accreditation procedure. There is a problem if the values are out of range. Owing to the differences in results of the alkane mix no QC investigation was carried out (Grob & Barry, 2004) In EIC, m/z ratio representing the targeted analytes are extracted from a data set obtained from GC-MS run (Basic, Boyd & Bethem, 2013). A plot of the data produces peaks around a specific mass to charge ratio of an analyte. Mass tolerance is dependent on the mass accuracy, mass resolution and mass spectrometry of the instrument used in collection of the data. This is important in detection of the analytes, highlighting the potential isomers and in resolving co-elute substances (Lee and Zhu, 2011). The debris sample collected from the site of fires is analysed through GC-MS process to establish the presence of ILR. The ion chromatogram together with the ion profiles of selected compound extracted is compared with a standard collection of IL to establish the presence of ILRs (Kobilinsky, 2012; Basic, Boyd & Bethem, 2013). On the other hand, the identification is made complicated by various factors such as evaporation of the liquid, the technique used to extract the liquid and interferences in the liquid matrix. The volatile liquid evaporates due to heat. This alters the chemical composition of the liquid. As a result, the chromatogram of the liquid that has been evaporated would be different from that which has not been evaporated. Petroleum based products or hydrocarbons in a debris sample and the products obtained from thermal degradation can also introduce thermal interferences of the ILR extracted. The differences in liquid extraction from the matrix compared to the standard procedure may also result in the difference (Kobilinsky, 2012; Armarego & Chai 2012). In order to solve the problem of evaporation and interference, the standard collection can be expended to include different levels of evaporated chromatograms of liquid, and chromatograms of burned and unburned household samples. Although this procedure assist in the identification of the origin of some of the extra peaks in the chromatogram of the samples, visual identification of chromatograms is still complex (Schmidt & Symes, 2008; Mohrig, 2003). Conclusion In this practical, GC-MS has used to analyse IL through extracted ion chromatography (EIC). Hydrocarbons comprised mainly of alkane and aromatic compounds. The main advantage of the technique used here is that it is nondestructive as the items can be re-extracted a number of times without losing its value. Therefore, if the extracts appear distorted, displaced or too weak, it can be re-extracted to obtain better sample representation. The sample were analysed using GC-MS in the monitoring mode in order to reduce the matrix interferences and the data was analysed based on different standard variables. The statistical procedure was done on the chromatogram instead of using selected sections of the chromatogram in order to avoid elimination of the potential valuable variables that permits the discrimination of the simulated ILRs. It has been shown that the use of full chromatogram eliminates any subjectivity related to selection of a given variable in data analysis. Solvent blank was also used to ensure that the extraction was not contaminated. The identification was made complicated by various factors such as evaporation of the liquid, the technique used to extract the liquid and interferences in the liquid matrix. The volatile liquid evaporates due to heat. This alters the chemical composition of the liquid. As a result, the chromatogram of the liquid that has been evaporated would be different from that which has not been evaporated. To solve these problems, the standard collection can be expended to include different levels of evaporated chromatograms of liquid, and chromatograms of burned and unburned household samples. References Almirall J.R. and Furton K. G., (2004). Analysis and Interpretation of Fire Scene Evidence, Forensic Science Techniques, CRC Press, Armarego, W. L. F., & Chai, C. L. L. (2012). Purification of laboratory chemicals. Oxford: Butterworth-Heinemann. Basic, C., Boyd, R. K., & Bethem, R. A. (2013). Trace quantitative analysis by mass spectrometry. Hoboken, N.J: Wiley. Bogusz, M. J. (2008). Forensic science. Amsterdam: Elsevier. Chandler, R. K. (2009). Fire investigation. Australia: Delmar Cengage Learning. Daeid N. N., (2004). Fire Investigation, International Forensic Science and Investigation, CRC Press De, H. E., & Stroobant, V. (2013). Mass Spectrometry: Principles and Applications. New York, NY: John Wiley & Sons. Grob, R. L., & Barry, E. F. (2004). Modern practice of gas chromatography. Hoboken, N.J: Wiley-Interscience. Hartmann, D. L. (1994). Global physical climatology. San Diego: Academic Press Kobilinsky, L. F. (2012). Forensic chemistry handbook. Hoboken, N.J: John Wiley & Sons. Lee M. S. and Zhu M., (2011). Mass Spectrometry in Drug Metabolism and Disposition: Basic Principles and Applications Lichtfouse, E. (2005). Environmental Chemistry: Green chemistry and pollutants in ecosystems. Berlin [u.a.: Springer. Hartmann, D. L. (1994). Global physical climatology. San Diego: Academic Press. Hübschmann, H.-J. (2014). Handbook of GC/MS: Fundamentals and Applications. Weinheim, Bergstr: Wiley-VCH. McMaster, M. C. (2005). LC/MS: A practical user's guide. Hoboken, N.J: John Wiley & Sons. Mohrig, J. R. (2003). Techniques of the organic laboratory: Miniscale, standard taper microscale, and Williamson microscale. New York: W.H. Freeman. Newman, R., Gilbert, M. and Lothride, K. 1998, GC-MS guide to ignitable liquids, CRC press, Boca Radon; London. + ASTM Method) Patnaik, P. (2007). A comprehensive guide to the hazardous properties of chemical substances. Hoboken: John Wiley. Schmidt, C. W., & Symes, S. A. (2008). The analysis of burned human remains. Amsterdam: Elsevier/Academic. Stauffer, E., Dolan, J. A., & Newman, R. (2008). Fire debris analysis. Amsterdam: Academic Press. Read More

The debris like the activated charcoal contains adsorption sites. The adsorption bond produced between the debris and higher molecular weight hydrocarbons preludes volatization even at higher temperatures. This technique cannot be able to differentiate between diesel within the range of C9 to C23 and kerosene in the range of C9 and C18 (Almirall and Furton, 2004). The main advantage of the technique used here is that it is nondestructive. This means that the items can be re-extracted a number of times without losing its value.

Therefore, if the extracts appear distorted, displaced or too weak, it can be re-extracted to obtain better sample representation (De & Stroobant, 2013). The sample were then analysed using GC-MS in the monitoring mode in order to reduce the matrix interferences and the data was analysed based on different standard variables. The statistical procedure was done on the chromatogram instead of using selected sections of the chromatogram in order to avoid elimination of the potential valuable variables that permits the discrimination of the simulated ILRs.

The use of full chromatogram eliminates any subjective effects related to selection of a given variable in data analysis. Solvent blank was used to ensure that the extraction was not contaminated (Stauffer, Dolan& Newman, 2008). Gas chromatography is used to identify various components through the use of retention time and pattern recognition, which is a visual composition of chromatograms (Chandler, 2009). Pattern recognition requires removal of human bias, since data interpretation is carried out through visual inspection.

Potential interferences vary depending on the matrix they are derived from. The chromatographic data is complicated by the change in composition due to heat exposure. Due to high interference level due to pyrolysis and low concentration of analytes, mass spectrometer extracts the analytes selectively (Chandler, 2009; De & Stroobant, 2013). GC-MS provides specific information of single components found in a sample of debris, but many GC peaks contains a mixture of two or more hydrocarbon components like as shown below for casework sample.

GC can provide information about the identity of the components in a given sample using common fragmentation pathways that is unique for each substance. Mass chromatography assists in recognizing the molecular mass of those ions (Hübschmann, 2014). The retention time for each sample and their m/z ratio are shown below. Dodecone Decane 1, 2,3 tmb The peaks are used to determine if the ILR is present or absent, are known through their mass spectrum. This can be accomplished through pattern matching of the ion chromatography extraction.

The extracted ion chromatography are compared with the known standard of IL or a specific compound can be identified by mass spectrum and compare them to the mass spectrum of the known standard. This process of characterization of IL is done according to the ASTM scheme (ASTM E1618-10). The following table shows the Rt for different target molecules (Daeid, 2004; Schmidt & Symes, 2008). ILR can be identified if there are significant peaks in the chromatogram which may be attributed to the sample matrix.

If the peaks do not match that of the standard peaks for ignitable liquid it is regarded to be negative. Total ion count The ion mass spectrum for 1, 2, 4-trimethylbenzene, m/z = 120. 1, 2, 3-trimethylbenzene which is C3 – alkylbenzene lies right next to the C4 and C5-alkylbenzene. From the table above, the area for C5-alkylbenzenes with m/z of 148 is not very specific for the selected parent ion m/z Decane, n-dodecane, adakane12, CH3(CH2)10CH3, Dihexyl, n-Dodecane, Duodecane Quality control -This is performed to ensure the consistency of an instrument in reporting the sample results.

It is done in the lab following accreditation procedure. There is a problem if the values are out of range. Owing to the differences in results of the alkane mix no QC investigation was carried out (Grob & Barry, 2004) In EIC, m/z ratio representing the targeted analytes are extracted from a data set obtained from GC-MS run (Basic, Boyd & Bethem, 2013).

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