Forensic investigations: defined by applications of principles to matter (Merriam, 2019). Examined through analytical techniques; procedures for analysis of facts, issues, or status- generally are tasked and time-limited (ManagementMania, 2016). However, with increased effectiveness- accuracy of findings will intensify and limitations will decrease.
Chromatography is a technique used within forensics- separating components of a chemical mixture relying on the differential affinities of substances for a mobile and an absorbing, stationary medium which they pass (Farlex, 2020).
This fundamental concept: the mixture theory- A hypothesis justifying that mixtures are symbolize through “categorisations of bodies; all of which simultaneously inhabit regions of space” (Woodford, 2017). Consequently, correlating to Chromatography through particular techniques- determining rates of migration of samples through columns (Woodford, 2017). Absorbance of molecules rapidly when distributed by the surface of liquid indicates slower travel rates to the stationary phase; whereas those with lower affinities travel faster through the mobile phase and, therefore dispersed faster within the stationary phase (Woodford, 2017).
The improved preparative; High performance liquid Chromatography (HPLC) identifies, separates, and quantitates dissolved liquid chemical compounds (biological specimens, environmental samples, medicinal chemistry and microbiology) from mixtures of compounds (Elsevier, 2020). Mixture separation is achieved by pumps forcing solvents through at pressures of ‘400 atmospheres’ to stationary phase- granular, solid particle material (Koester, 2016). Hence, an enhanced surface area for the interaction of smaller particles between this phase and the flow of passing molecules (Koester, 2016). As the eluent exists the column, substances separate into distinct fractions (Koester, 2016). Therefore, HPLC can be applied within forensics as drug analysis, toxicology, fibres and explosives (GMU, 2019).
Whereas, Gas Chromatography (GC) is utilised through separation and vaporisation of organic compounds (biological samples, environmental samples, and solvent extractions) without decomposition (Davis, 2019). This procedure occurs when vaporised samples are injected and carried through inert gas (helium or nitrogen) (Davis, 2019). Consequently, traveling through glass silica columns coated with solutions- less soluble samples within liquids result with faster data collections, compared to those with greater solubility (Davis, 2019). Therefore, GC determines a person’s death by analysing blood and fibres within forensics (Davis, 2019).
Thus, throughout this conducted research the aptness of Chromatography as an effective analytic technique used in forensic investigations will be analysed.
Undoubtedly, both analytical techniques are appropriate within modern forensic sciences for quantitating mixtures; considering the 35 million cases reported on alcohol and illicit substance abuse within 2019 (Davis, 2019).
HPLC systems utilise the data analysis- chromatogram (GMU, 2019). Chromatograms consist of graphs examining accurate signals in detectors- “peaks”; portraying samples concentrations (GMU, 2019). Thereby, HPLCs specific “peaks” when perceived provide sufficient findings towards modern sciences- Appropriately conducting ‘purification’ of mixtures (GMU, 2019).
GC, however, enables elements of compounds to separate into distinct parts; the observation of elements reaction rate with specific solvents can be analysed and identified by “retention times” (labmate, 2014). Thus, “retention times” are applied due to efficiency when determining fluids presented inside bodies after death and therefore due to this sufficiency further investigation is unnecessary (Labmate, 2014).
Strengths and Limitations
When considering HPLCs purpose- strengths are innumerable as this is a highly versatile, analytical technique within forensics (Smith, 2018). HPLC is known for speed and efficiency’; relying on compound separation through pumps rather than gravity which, however, utilised as advantages; ensuring approximate 10-30-minute division of mixtures into distinct fractions (Smith, 2018). HPLC is also versatile within analysis of mixtures- as previously stated; towards forensics, providing credible data (Smith, 2018).
However, this method is relatively costly- estimated $500/month (Smith, 2018). Consequently, requiring high-priced instruments for ‘purification’ as well as limitations to only dissolved liquid compounds and timing complexions associated with fraction collectors (Smith, 2018). Coelution may also be a limitation- thus manifesting difficulty when determining which portion of mixture eluted at any precise point (Smith, 2018).
While GC is less complexed the efficiently through accurate findings within 30 minutes is present (Linkedin, 2020). Strengths may include, accuracy, speed and requirements of only small samples (Linkedin, 2020). GCs inert gas is also ethical, safe and universal, therefore, environmental hinderances are excluded during conduction (LInkedin, 2020).
Nevertheless, although GC is effective within forensics, limitations also occur (Linkedin, 2020). GC limits to organic compound mixtures as well as larger expenses- $150,000 (Linkedin, 2020). (Linkedin, 2020). GC also restricts to one analysis, therefore, decreasing versatility towards forensics (Linkedin, 2020).
Overall, both HPLC and GC are highly precise when considering its purpose of quantifying chemical components (Smith, 2018). Due to their vital stationary and mobile phase methods- precisely enabling chromatographic separation occurrence (Smith, 2018). Consequently, since mixtures are disseminated through both phases, forensic scientist have the ability to precisely analyse Volatile substance properties and density due to their possible affinities; portraying accurate fractions- due to mixture separation through similarities, acquired from GC and HPLC (Smith, 2018). Thus, high precision is secured towards analysis of both techniques findings towards forensic investigations (Smith, 2018).
This study investigated Chromatography is an effective analytic technique used in forensic investigations. As concluded HPLC and GC are sufficient and appropriate techniques; revolutionising findings within forensic through utilising relativity within mixture theory to accurately separate organic compounds (Smith, 2018). Undoubtably both techniques provide credibility to this statement through reliability, safety, fairness, and ethical actions managed to precisely portray HPLCs distinguished “peaks” and GCs retention rates through phases stationary and mobile (Smith, 2018). However, limitations may occur and include complexity, high expenses, or decreased diversity within fields of forensics. This illustrates decreased accuracy and effectiveness of data.
Nonetheless, further advancements and can be implemented to these techniques to reinforce findings. Including decreasing column sizes- producing higher “peaks” and therefore, resolve closely eluting “peaks” or boosting carrier gas linear velocity- increasing speed rates (Smith, 2018). Therefore, effectiveness and security of both techniques towards mixture separation within forensics will intensify (Smith, 2018).
- Davis. (2019, September 3). Instrumental analysis of chromatography. Retrieved from Analytical chemistry: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Instrumental_Analysis/Chromatography/Gas_Chromatography
- Elsevier. (2020, January 3). high-performance-liquid-chromatography. Retrieved from biochemistry-genetics-and-molecular-biology: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/high-performance-liquid-chromatography
- Farlex. (2020, January 27). What is chromotography. Retrieved from The free dictionary: https://www.thefreedictionary.com/What+is+chromotography%3F
- GMU. (2019, August 27). HPLC. Retrieved from HPLC tutorials: http://www.gmu.edu/depts/SRIF/tutorial/hplc/qual.htm
- Kevin. (2019, November 19). techniques and technology in HPLC. Retrieved from ap chemproject forensic chemistry: https://www.hindawi.com/journals/ijac/2019/1851796/
- Koester. (2016, July 10). What is HPLC. Retrieved from Chemistry reviews: https://www.chemistryviews.org/details/education/9464911/What_is_HPLC.html
- Labmate. (2014, October 10). How is gas chromatography used witin forensics. Retrieved from Chromatography today: https://www.chromatographytoday.com/news/gc-mdgc/32/breaking-news/how-is-gas-chromatography-used-in-forensics/30185
- Linde. (2020, April 2). High performance liquid chromatography. Retrieved from Analytical methods: http://hiq.linde-gas.com/en/analytical_methods/liquid_chromatography/high_performance_liquid_chromatography.html
- Linkedin. (2020, April 18). Advantages and disadvantages of GC. Retrieved from Slideshare net: https://www.slideshare.net/mostafaokda255/gas-chromatography-67507533
- Managementmania. (2016, May 7). Forensic Science. Retrieved from Merriam webster: https://managementmania.com/en/analyses-analytical-techniques
- Merriam. (2019, April 1). Analyse analytical technique. Retrieved from Managementmania: https://www.merriam-webster.com/medical/forensic%20science
- NCBI. (1998, June 17). Comparison between GC and HPLC. Retrieved from Forensics used within analytical techniques: https://www.ncbi.nlm.nih.gov/pubmed/9627371
- Sheffield. (2019, March 3). Gas chromotography. Retrieved from Chemistry tutorials: https://teaching.shu.ac.uk/hwb/chemistry/tutorials/chrom/gaschrm.htm
- Smith. (2018, December 1). DIsadvantages and advantages of HPLC. Retrieved from Forensic science: https://sciencing.com/disadvantages-advantages-hplc-5911530.html
- TSOW. (2020, January 25). High-Performance-Liquid-Chromatography. Retrieved from HPLC explained: https://www.waters.com/waters/en_AU/HPLC—High-Performance-Liquid-Chromatography-Explained/nav.htm?cid=10048919&locale=en_AU
- Wardencki. (2000, December 27). Gas chromatography. Retrieved from Science direct: https://www.sciencedirect.com/topics/materials-science/gas-chromatography
- Woodford. (2017, June 30). Chromatography work. Retrieved from Science: https://sciencing.com/chromatography-work-21200.html