Recrystallisation and Chemical Separations Essay

After the serial dilutions of the red and blue dyes were taken, the molarity and absorbance for both dyes were calculated. Using the MiVi = MfVf equation, the concentrations for each value of the red and blue dye were separately calculated. Calculating absorbances calls for setting the correct wavelengths of light for each dye. In this case, the 470 nm wavelength for red dye and the 635 nm wavelength for blue dye was needed to find the maximum absorbances. The absorbance was found by blanking the colorimeter and entering the concentrations. After both values of the absorbances and concentrations were found, the values were then graphed in order to obtain the equation of the relationship between absorbance and concentration.

The purpose of this experiment is to determine the maximum absorbance of fast green, and the chlorophylls, also in the case of fast green create a concentration curve to determine an unknown substance. Each test will use the spectrophotometer.

In this task the concentration of an unknown sample of copper sulphate using colorimetry was used to find the concentration. In this investigation copper sulphate was used which is CuSO4.5H20 as a formula. To make a standard solution which was 1M, the same clean equipment was used to make up the standard solution as used to make sodium carbonate. However there was one difference and that was that the hot distilled water was used to dissolve the copper sulphate crystals. There had to be enough hot water in order to dissolve the crystals into the beaker and then add cold distilled water to cool the solution.

Recrystallization is a technique frequently used in organic chemistry to purify solid organic compounds. The goal of this technique is to allow organic compounds to form crystal lattice structures, and to remove any of the impurities that do not align within this crystal structure.1 The theory behind recrystallization revolves around entropy; as heat will cause a organic compound to dissolve (increase in entropy), a decrease in heat will then allow that organic compound to reform (decrease in entropy) and become purer.2

Lycopene and β-carotene are separated using thin layer chromatography (TLC). A mixture of tomato paste containing dissolved lycopene and β-carotene is first spotted on a TLC plate. The technique uses a stationary phase layer, on which the substances stick, and a mobile phase, which migrates upwards the plate and carries the components of the mixture with itself (Chemguide). Depending on their respective polarity, lycopene and β-carotene stick more or less to the stationary phase and so they migrate up the TLC plate at different rates (Chemguide). Thus, as the chromatography is completed, the two components will appear as distinct dots at different heights on the plate. Lycopene has a bright orange color, whereas β-carotene is light yellow.

The product was placed in a Craig tube and several drops of hot (100°C) solvent (50% water, 50% methanol, by volume) was added and heated until all of the crystals dissolved. The Craig tube was plugged and set in an Erlenmeyer flask to cool. Crystallization was induced once the mixture was at room temperature by scratching the inner wall of the tube. It was then placed into an ice bath for ten minutes until crystallization was complete. The tube was then

21) After all of the solid dissolves, move the flask from the hot plate and allow it cool to room temperature. After a while, crystals should appear in the flask.

In the beginning of this experiment, our TA added water, salt, and 75/25 hexane/acetone to spinach leaves to a blender and blended the mixture to assume equal amounts for each group and to avoid erros if each student had to do the blending. The addition of the water to the mixture allowed the it to separate into a distinct organic layer after being run in a centrifuge, which was available to be collected at the top of the centrifuge. Salt reduces solubility, which will force the organic parts of the mixture (the desired pigments for example) to separate into the organic layer at the top. Lastly, 75/25 hexane/acetone is added because this is a moderately polar solvent and will useful for both the non-polar and polar pigments present within the spinach leaves. A mixed solution of hexanes and acetone must be used because acetone is very polar, while hexane in very non-polar, and the spinach leaves contain both non-polar and polar pigments in them that are important in the extraction and for further analysis. The mixture was placed in the centrifuge so the solids in the mixture (mostly cellulose) could be separated from the liquids into separate distinct layers for further extraction and testing. In the tube, the organic substances separated into the top layer, whereas the water layer remains at the bottom of the tube below the solid layer made up of mainly cellulose.

Pigments extracted from different greens have different polarities and may be different colors. Mixed pigments can be separated using chromatography paper. Chromatography paper is able to separate mixed pigments due to their polarity and solubility. Pigments of chlorophyll a, chlorophyll b and beta carotene will be separated on chromatography paper because each has its own polarity and solubility, which results in different distance traveled up the paper. Beta carotene is non-polar so it travels the highest distance, followed by chlorophyll a. Chlorophyll b is the most polar; therefore, it travels the shortest distance. The separated pigments on the chromatography paper can be eluted in acetone and absorbance spectrum is

Abstract. Thin Layer Chromatography is a simple procedure that allows you to determine how many and what kind of compounds are in a mixture. By understanding the properties of the TLC system and how it combines with the functional groups of amino acids the retardation factor (Rf) values can be calculated and compared to specific hydropathy values of amino acids. Thin layer chromatography is used to separate and recognize a certain compound. The silica gel that is located on the outside of the TLC sheet functions as the stationary phase and the solvent mixture functions as the mobile phase.

Using the extracts that were prepared the absorption of each sample were tested at 10 nm intervals from 410 to 740 nm. As a result of absorption, despite the difference in pigments both the ivy in the shade and the ivy in the sun have green colored pigments. However, the ivy in the shade has a consistent wavelength of pigments while the ivy in the sun has an inconsistent wavelength of pigments. There was no change in the spectrophotometry wavelength reading of each ivy sample in the shade. The wavelength value of the ivy in the shade was 2.50 absorbance. There were many changes in the spectrophotometry wavelength reading in each ivy sample in the sun. Those values range from 2.50 absorbance to 1.80 absorbances. The larger the wavelength tested, the less of an absorbance each sample produced. Each pigment has hydrophobic and hydrophilic properties that affect its movement in the liquid mobile phase as compared to its stickiness for the solid non-mobile phase. The ratio of the distance traveled by

iii. Rinsing the recrystallized material on the filter with room temperature solvent could have negative effects on the results of the recrystallization because even room temperature solvent can dissolve the solute (recrystallized material) It is always necessary to use cold solvent as it cannot dissolve the solute.

INTRODUCTION The result of the peripatetic nature of electromagnetic radiation through a prism, or the spectrum, concluded the six distinctive colors: red, orange, yellow, green, blue, and violet.1,5 These spectrum colors have been noted as constants of color that measure luminosity, chroma, and wavelength.5 Wavelengths, in the range of 400-750 nm, have been ascertained by the absorbance spectrum due to the way for which light is absorbed by a compound, such as food dyes, and how the observed color tends to complement the absorbed color, i.e. red paired with green, orange with blue, and yellow with violet.2,3 Food dyes, added to foods and beverages to provide a certain appearance and to meet customer expectations, have correlated to the absorbance

The purpose of this experiment was to take spinach leaves and extract the chlorophyll and carotenoid pigments by using acetone as the solvent. The chlorophyll and carotenoid pigments were extracted by using column chromography and alumina was used as the solvent. Solvents of different polarities were used, starting with the least polar, to extract the certain components from the leaves. They were then analyzed by using thin- layer chromatography.

Chromatography Investigation Chromatography is a highly regarded technique used to separate the components of a mixture. It is based on the principle that each component possesses a unique affinity for a stationary phase and a mobile phase. The components that are more inclined to enter the mobile phase will migrate further on the chromatogram and distinguish themselves from the other components. The type of solvent used in chromatography is known to directly affect the separation of the mixture. In this experiment, thin-layer and column chromatography will be utilized to separate the numerous chlorophyll and carotenoid pigments of a spinach extract.