Chromatography By Phivy Semyonovich Tswett

Background: Paper chromatography is one method for testing the purity of compounds and identifying substances. Paper chromatography is a useful technique because it is relatively quick and requires small quantities of material.

Adsorption chromatography occurs when “one substance form[s] some sort of bonds to the surface of another one”, creating intermolecular forces between the two substances (Chemguide). For thin layer chromatography, the components of the mixture are adsorbed onto the stationary phase that covers the plate (Chemguide). The more polar a substance is, the more strongly adsorbed it is (Chemguide) and the strong intermolecular forces then result in a slower rate of migration with respect to the moving phase. As the solvent touches the TLC plate, the solute (mixture) is allowed to move up the TLC plate

The purpose of this experiment is to practice common organic laboratory techniques inside the lab to get one oriented to the basic methods of procedure that can be used for later experiments. This experiment involves the separation of benzoic acid from a more crude form, consisting of benzoic acid, methyl orange, a common acid/base indicator, and cellulose, a natural polymer of glucose (Huston, and Liu 17-24). The technique that is used to perform this separation is called extraction. Extraction is a systematic process of separating mixtures of compounds, taking advantage of the affinity differences of compounds to separate them (Padias 128-37). This technique recognizes the principle that “like dissolves in like,” that is,

(a) (3 pts.) This video discusses 3 different types of chromatography. List each one mentioned, and describe their differences in as much detail as possible (your points earned will be proportional to the level of detail in your discussion). Which one was used in this lab demonstration?

2. 3 real-world uses for paper chromatography include forensic testing, performance enhancing drug testing, and Ebola immunization.

Chromatography is a fairly simple process. First, you put a dot of ink(or in our case, the M&M food dye) near the bottom of some chromotography paper (also known as filter paper), and then hang the paper vertically with its lower edge (the one closest to the spot of dye) dipped in a solvent (In our case, the sodium chloride solution). Capillary action forces the solvent to travel up the paper, where it meets and dissolves the ink. The dissolved ink (which is the mobile phase) slowly travels up the paper (the stationary phase) and separates out into its different elements. Another way of describing it is to think of the liquid as an adhesive-like liquids, some of which stick more to the solid and can travel more slowly than others. This is

Multiple extractions with smaller volumes are more efficient than a single extraction at a one large volume. When an organic solvent is used to extract a compound from the aqueous solvent, smaller volumes will result in a better extraction. The success upon the collection of the crude material is depended on how well the water is absorbed by the anhydrous drying material. The presence of the drying material correlates with the vapor pressure of the other compound. When the vapor pressure is low, there is a smaller amount of moisture in the gas produced. Once the anhydrous material is added and clumping was avoided, the evaporation of the added organic substance can proceed. The final material collected can be physically identified by the final color of the precipitate. A greenish- white precipitate is most likely identified to be pure, and a brownish color indicates that the collected material is wet, and not

In 1941 Martin and Synge, described the discovery of liquid-liquid partition chromatography and also laid the foundation of Gas liquid chromatography and High performance liquid chromatography. They also introduced the concept of the Height Equivalent to the Theoretical Plate, which has since been adopted as the measure of Chromatographic efficiency.

The boiling point of a compound is often related to its polarity (see also polarity chapter). The lower the boiling point is, the higher the vapor pressure of the compound and the shorter retention time usually is because the compound will spent more time in the gas phase. That is one of the main reasons why low boiling solvents (i.e., diethyl ether, dichloromethane) are used as solvents to dissolve the sample. The temperature of the column does not have to be above the boiling point because every compound has a non-zero vapor pressure at any given temperature, even solids. That is the reason why we can smell compounds like camphor (0.065 mmHg/25 oC), isoborneol (0.0035 mmHg/25 oC), naphthalene (0.084 mmHg/25 oC), etc. However, their vapor pressures are low compared to liquids (i.e., water (24 mmHg/25 oC), ethyl acetate (95 mmHg/25 oC), diethyl ether (520 mmHg/25 oC)).

Filter paper in a glass funnel will catch the solids and allow you to isolate a pure sample, sodium chromate in this case, that was formed during a chemical reaction.

     Conventional Liquid Chromatography is most commonly used in preparative scale work to purify and isolate some components of a mixture. It’s also used in ultra trace separations where small disposable columns are used once and then discarded. Analytical separations of solutions for detection or quantification typically use more sophisticated high-pressure liquid chromatography instruments.

The two pentenes were trimethyl-1-pentene and trimethyl-2-pentene. The methods to reach this conclusion were different, then those used in the thin-layer chromatograph. A gas chromatograph consisted of a gaseous mobile phase, carrier gas, and a non-volatile liquid as the stationary phase in a heated system that collected its results from a flame ionized detector. A thin-layer chromatograph consisted of a volatile liquid mobile phase, and a silica layer on an absorbable paper as the stationary phase. The results of the TLC was observable on the TLC plate after the separation, as a graph was needed to physically see if the compounds in the gas chromatograph were separated. These differences in procedure relates to the type of chromatography that was needed to separate specific compounds based on their unique or similar

The following procedure dealt with a chromatogram. The materials needed are: a pencil, safety goggles, scissors, chromatography paper strip, capillary tube, spinach plant pigment extract, test tube, cork stopper, graduated cylinder, chromatography solvent (alternative isopropyl alcohol), metric ruler, stopwatch or clock with a secondhand, hook/fashioned paperclip, paper towels, test tube rack, and mortar and pestle. First we obtained a strip of chromatography paper and cut it so it would fit inside a test tube (with it barely touching the bottom of the tube). Also, when touching the strip, touch the sides only. Then we attached (firmly) the top of the strip to a hook (or fashioned paperclip at bottom of the cork stopper). Make sure it fits in the test tube. Next we used the pencil to draw a faint line across the strip two centimeters from the bottom tip of the strip. We placed the cork and strip in place, and we put a mark on the test tube one centimeter below the top of the stopper.

Gel-Filtration Chromatography is a commonly used method used in order purify a protein from a mixture, by means of separations. Different biomolecules differ in size, or their molecular weight. In the gel matrix inside the chromatography column, there are gel beads which are porous to allow certain sized molecules to enter. The molecules that are able to enter the pores of the gel, are held in stationary phase and will elute from the column later on, these are usually smaller, to medium sized molecules. Larger molecules that are not able to fit in the pores will elute out of the column first, they are involved in mobile phase where they just go straight through the column without interacting with the gel beads. Smaller molecules will have a higher elution volume, while the larger molecules will have a lower elution volume. The volume to elute the protein is inversely proportional to the molecules size.

AIM : Thin-Layer Chromatography can show many different characteristics of a mixture. It is recognized for isolation , separation ,identification, and anaylsis of the mixture’s components. The purpose of this experiment is to separate carbohydrates into its pure components such as mixtures of monosacrides by TLC. TLC is used to identify sugars in normal and pancreatic disease urine, the procedure is easy and reproducible .