Distinction Level BTEC Applied Science Assignment C, Chromatography (Verified)

Distinction Level BTEC Applied Science Assignment C, Chromatography (Verified) Chromatography : a method used to separate chemical mixtures for analysis Soluble :solubility is the degree to which a substance dissolves in a solvent to make a solution Solvent : the substance in which a solute dissolved to produce a homogeneous mixture Mobile phase : the liquid that transports the substance mixture through the absorbing material which travels along the stationary phase and carries the substance components with it Stationary phase : the solid material that absorbs the mixture flowing through it Adsorption : the process by which atoms, molecule or ions from a gas or liquid adhere to a surface the process is not permitted Chromatogram : the resulting paper or plate produced showing the substance Immiscible: liquids that do not mix together Porosity : a measure of the volume of tiny holes in a material divided by the total volume of the material measuring rf values When the solvent front reaches the top of the TLC plate or chromatography paper, it is measured to determine how far it has travelled. We can tell how far the solution has moved and how far the spots have migrated by calculating the rf. Draw a line from the solvent front to the original line and measure it with a ruler to see how far the solvent has travelled. Then draw a line from the middle of the spot to the original line and measure it again with a ruler. This would display how far the spot has travelled. This equation may be used to calculate the rf value. rf= distance travelled by substance/ distance travelled by solvent font Polarity Thin layer chromatography produces more usable chromatograms than paper chromatography because it shows more separation of the components in the mixture, making analysis easier. The distance travelled by the sample is determined by the size of the molecules. Larger molecules require more time to migrate up the TLC plate or chromatography paper, whereas smaller molecules are more mobile. The solvent you choose influences how far the spot travels in the same way that the polarity of the molecule affects how far the spot travels. Polar molecules are more attracted to polar solvents and so travel further if a polar solvent is used instead of a non-polar solvent. paper chromatography of plant pigments I conducted a practical to investigate the techniques and separation methods used in paper chromatography to detect the pigment in spinach leaves aim: Using paper chromatography to identify the pigments in spinach leaves Pigments may be split into different colour bands using paper chromatography. Chromatography is the separation of a mixture into its elements. Separation occurs by absorption, and capillarity pushes the mixture up the paper at various speeds. On the paper, the pigments separate and appear as coloured streaks. The pattern of separated components is referred to as a chromatogram. cautions o avoid poisonous or expired plants o make sure to organise the leaf by type e.g. sample of spinach leafs , sample of maple leafs o for a higher concentrated solution find the grana and chloroplast of the plant o chromatography solvent like propane are flammable , make sure that no flames are open as this can lead to a hazard o make sure to do the chromatography in a well ventilated room as this would avoid inhalation of the fumes equipment needed in paper chromatography o safety goggles o chromatography solvent ( propane ) o chromatography paper or filter cut into rectangle strips . 1cm x 15cm o fresh spinach o chromatography chamber o capillary tube o pencil and ruler o paper clip or tape o mortar and pestle o sand procedure for a paper chromatography prep: The leaves should be grouped into type. Take, for example, a sample of spinach leaves and a separate sample of maple leaves. Attach the paper inside the chromatography cylinder with a paper clip or tape. Be certain that the paper does not come into contact with the inside of the beaker containing the spinach leaves. This permits us to conduct a fair test because we are only experimenting on spinach leaves and not any other leaves. 1. Cut the filter paper or chromatography paper into a rectangle form that fits within the chromatography cylinder. 2cm from the bottom of the paper, draw a thin pencil line. This would be your starting point. 2. The spinach leaf should be cut into little pieces, the size of a button. Place them in the mortar along with a pinch or two of sand. It is included to assist in the grinding process. Then, using a pipet, add around 5ml of propane. Then, using the pestle, grind the leaves in a circular motion until a fine mixture forms. The liquid contained in the leaf pigments has now been dissolved in the pigment extract. 3. Apply a little drop of the extract to the centre of the pencil line on the paper strip using a capillary tube. Using a hairdryer, dry the drop. Then repeat the process twenty times more. This is done to concentrate and build up the pigment in a single area. Important: After placing the spot, let the dot to dry. This prevents the pigment dot from spreading out too much. 4. Fill the chromatography cylinder with 5ml of propane. Attach the paper to the interior of the chromatography cylinder with a paper clip or tape. Make certain that the paper does not come into contact with the inside of the beaker. Ensure the paper just slightly touches the solvent and not the tube's side. The pigment dot must be above the solvent level. then watch the solvent ascend up the paper, carrying and separating the pigments as the solvent rises . Remove the paper as soon as the solvent reaches the top and let it to dry. Take note of the coloured bands. as the bands on the dry strip can be identified and labelled. On a data sheet, I entered the leaf species as well as the colours produced