Tank Chromatography
Introduction:
Chromatography is a method used to separate both organic and inorganic
compounds so that they can be analysed. Scientists often use
chromatography to figure out which basic constituents makes up a
specific mixture. Chromatography relies on the principle of selective
absorption.
A botanist named M.S. Tswett in 1906 first discovered chromatography.
Tswett used a method called 'column chromatography' to separate
chlorophylls by pouring petroleum-ether extract of green leaves into a
column of powdered calcium carbonate. The compounds slowly move
downwards through the glass column and each compound of the
chlorophyll is absorbed into beds at different heights depending on
their individual absorption affinity.
Forensic scientists heavily rely on chromatography currently when
solving crimes. It is also used for various purposes such as
determining the presence of cocaine in urine, alcohol in blood and how
much lead there is in water. Each of these are very important uses and
chromatography is the method chosen as it is very reliable and easy to
perform.
Aim:
Our aim was to use paper chromatography to separate various inks (both
permanent and water based) into their core pigments. We could use the
formula Rf = the distance moved by each solute (measured to the centre
of each solute stain) / the distance moved by the solvent. This would
give us the Rf values for each pigment in the ink. These Rf values
should be constant for each individual pigment.
Apparatus:
Ø Chromatography Paper
Ø Three permanent pens (Red, Green, Blue)
Ø Three water based pens (Red, Green, Blue)
Ø Chromatography tank pre-filled with acetone
Ø Drying Rack
Ø Pencil (for various markings)
Ø Scissors (used for serration)
Ø Ruler (used for all measurements)
Ø Bag Ties
Method:
The base of the chromatography paper was marked and then cut to form a
serrated edge. This edge was made to ensure that there was a
controlled flow of acetone up the chromatography paper.
Around 1902, when luminol was first synthesized, scientists noticed that it exhibited a blue glow in the presence of other compounds. Later on, it was found that the luminol reaction occurred in the presence of blood. Its use in crime scenes was first implemented by German forensic scientist Walter Specht in 1937. When the luminol solution is sprayed, the iron present in hemoglobin in blood catalyzes the reaction to produce a blue glow. This is used because in certain situations, there may be too little blood present at a crime scene to be able to be seen. It can also help when a suspect had attempted to “clean up” the blood after committing the crime. In these cases, luminol can be used to see any evidence of blood that cannot be seen with the naked eye. The glow from the reaction only lasts for about thirty seconds and requires dark conditions to be able to see, but investigators are able to document it in
Investigators can find clues from a murder through a number of different ways. Typically they find out how many times someone has been stabbed or however many blows they received. Through the count of the times the action had been performed they can come to an understanding of whatever hand the suspect was using. Other information can tell how the suspect was standing over their victim during the time of death. A common tool that forensic units use is the ultra violet or UV light. An ultra violet light can detect different areas that contain blood that might not be able to be seen in other conditions. Another common tool is the blood reagent test that forensics use on scene. These tests determine if the blood is human or animal. (Renee Blake)
During this time, it could only be used in a lab with semi-intense supervision. Now, fast forward a few decades and there are D.I.Y. at home kits. The process of Electrophoresis starts with an electric current being run through a gel containing the molecules of interest. The molecules will then travel through the gel in different directions and speeds, based on their size and charge, allowing them to be separated from each other. Dyes, fluorescent tags, and radioactive labels can all enable the molecules on the gel to be seen after they have been separated. Because of these identification markers, they appear as a band across the top of the gel. Electrophoresis can be used for many different things. It is used to identify and study DNA or DNA fragments, and helps us to better understand the molecular components of both living and deceased organisms. Electrophoresis can also be used to test for genes related to specific diseases and life altering diagnoses such as Multiple Sclerosis, Down’s Syndrome, kidney disease, and some types of cancer. Electrophoresis also plays a major role in the testing of antibiotics. It can be used to determine the purity and concentration of one specific type of antibiotic or several general antibiotics at a time. Electrophoresis is also extremely useful in the creation and testing of
1. In each case, is the ink a pure substance (based on your results)? Why or why not?
The primary methods when comparing forensic soil samples employ the use of microscopes and manually examining the colour, texture, density gradient and mineralogical content. After a primary manual examination has been conducted x-ray diffraction along with another method such as x-ray fluorescence are used to discover the chemical composition of the sample. These methods are considered to be useful for discriminating between samples which have inorganic minerals, however Bommarito et al (2006) believe a different method is needed to discriminate between organic compounds, high performance liquid chromatography (HPLC) satisfies these requirements Ion chromatography is also investigated in their study as it has not been applied to forensic soil comparisons before. ...
Experiment #3: The purpose of this experiment to test the chromatography of plant pigments the alcohol test strip test will be used.
The distance of the initial extract line to a pigment band was divided by the distance of the marked solvent front to the initial extract line both were measured in cm. The RF (relative to front) was calculated for each pigment band, indicating the travelled distance between the pigment and the front (solvent line) on the chromatography
Chromatography is a method to distinguish between organic and inorganic compounds so that they can be analyzed and examined. By performing analysis of a compound, a scientist can figure out what makes up the compound. Chromatography related techniques have been used for centuries to separate materials such as colorants extracted from plants. However, Chromatography was first developed in 1900 by Russian scientist Michael Tswett. He continued
The purpose of this lab is to determine the density of a solid and an unknown liquid in order to determine the unknowns from a list of substances provided in the lab instruction. A method to identify the substance is to figure out the density (d=m/v) where d is the density equals to the mass divided by the volume of the substance. When measuring the mass, reset the balance to zero to obtain only the mass of the object in grams (g) and not anything else. When measuring the volume, read at the meniscus for an accurate measurement.
To undertake titration and colorimetry to determine the concentration of solutions By carrying out titrations and colorimetry, the aim of this investigations was to use these methods such that the concentrations of different solutions used can be identified, and to help find the concentration of the unknown solution that were given. Using Titration and colorimetry the concentrations of different solutions in general can be determined and this helps to identify solutions with unknown concentrations. In this assignment I was asked to carry out two different scientific techniques and find the concentration of different solutions.
As explained by Saferstein “Chromatography is a means of separating and tentatively identifying the components of a mixtur... ... middle of paper ... ... ively place the suspect or perpetrator behind bars. Analyzing soil compounds can be measured by the levels of organic molecules including n-alkanes, fatty alcohols and fatty acids, which are all found in the waxy outer layer of plant matter (Geddes, 2008). It basically states that compounds can remain in the soil for thousands of years, which explains that each area being tested has its unique organic profile.
HPLC (High Performance Liquid Chromatography) is an analytical technique which separates a complex mixture of components into its specific individual components. It is a powerful tool in analysis, as it combines high speed with extreme sensitivity compared to traditional methods of chromatography because of the use of a pump which creates a high pressure and forces the mobile phase to move with the analyte in high speed. It is been used as a principle technology in various automated analyzers used for diagnostic purpose.
As seen on many crime shows and at real-life crime scenes, it is necessary to be able to identify DNA. Most of the time, this is done using a technique known as gel electrophoresis. Gel electrophoresis is a method used to separate the macromolecules that make up nucleic acids, such as DNA and RNA, along with proteins. Gel electrophoresis is significant because it has given scientists insight on what cells cause certain diseases and has led to advancements in DNA and fingerprint identification. My experiment will use gel electrophoresis to compare samples of natural and synthetic food dyes. The background for this experiment broaches the following subjects: inventors, real-world uses, necessary components, separation, and information on food dyes.
is impossible to specify a single best method to carry out a given analysis in
Forensic toxicologists employ a large number of analytical techniques to determine the drugs or poisons relevant to an investigation; the capacity of a laboratory to conduct routine toxicological analysis varies depending upon equipment, technical capability and analyst experience. When needed, there are specialty toxicology labs that can test for almost any potential toxin or metabolite in almost every kind of post-mortem sample. A laboratory should be accredited to perform the analytical work and must be subject to regular inspections. This will ensure that laboratories can reproduce accurate and reliable results for investigations. All laboratory tests conform to standard operating procedures, results are confirmed to meet standards, and reported results are peer reviewed by a second toxicologist before being released. Even so, we still use methods that Gettler used in his