Reference no: EM132555299

Experiment - Separating and Identifying the Active Ingredient of an Analgesic

Objectives -

To design a separation scheme which uses differences in physical properties of materials to separate the components of a drug using liquid - liquid extractions.

To quantify the amount of sugar and aspirin in the drug sample.

To identify and quantify the active ingredient in a drug sample.

Prelaboratory Tasks -

IN YOUR LAB NOTEBOOK:

a. Design a separation scheme (Flow chart) to separate and collect the sucrose, aspirin and active ingredient from the drug using the solvents given. You may use liquid extractions, filtration and solvent extractions. Prepare a flow diagram including all steps in the separation, collection and identification of the unknown. Stick this in your laboratory notebook. Use the experimental below and the introduction to help.

ON MOODLE:

a. Complete the Laboratory Planning Quiz. You will be given your unknown here.

b. Download the Spectra and TLC plates for you unknown.

c. View the videos on the moodle page on TLC, filtration technique and melting point determination.

Method for Thin Layer Chromatography -

1. Assemble a TLC Tank: You will need a small beaker, a piece of filter paper, a Petri dish, a pencil, a TLC spotter and a TLC plate. Place the filter paper around the inner wall of the beaker, pour 4 mL of the TLC solvent (ethyl acetate: hexane you will need to experiment to get the right ratio!) in the bottom of the beaker (to a depth of about 3 mm) and place the Petri dish over the top. The filter paper must be touching the solvent. The purpose of the filter paper is to help saturate the air inside the beaker with the TLC solvent.

2. Place two rice grain sized portions of your unknown in a vial and add approx. 1 mL of dichloromethane (CAUTION: toxic). Ensure the compound has dissolved.

3. Try not to touch the white side of the plate with your fingers. With your pencil (not pen!!!), mark a line across the plate, about 5 mm from, and parallel with, its bottom edge. Mark 4 points (e.g. "product", "pure acetanilide" & "pure paracetemol" and "pure phenacetin") on the line, equally spaced, with the outer ones at least 5 mm from the side of the plate (see figure attached).

4. Make a capillary spotter (See your demonstrator for this): Place a melting point capillary tube or a Pasteur pipette in the dark blue part of a Bunsen burner flame. Hold it there until it softens and starts to sag. Quickly remove the capillary from the flame and pull on both ends until it is 2-3 times its original length. If you pull the capillary inside the flame, you will have a "piece of art", but not a good spotter.

Allow the capillary to cool down, and then break it i n the middle. Make sure that you break off the closed end on one of them. Do not use gloves when you pull capillaries. You will have much better control without them!

5. Dip your capillary spotter in your unknown solution and you should see your solution rise up the tube. S pot it three times on the left mark, being sure to allow each spot to dry before adding the next one.

The aim is to get a very small concentrated spot of the solution. Take some of the pure solutions supplied and spot three times on the other marks. When the spots are completely dry, carefully place the plate vertically in the TLC tank, with the markings at the bottom. The solvent level must be below the level of the line. Cover the beaker with the Petri dish and allow the solvent to flow up the plate. When it is approx. 5 mm from the top of the plate, remove the plate and quickly mark the level the solvent reached. This is known as the "solvent front." Do not allow the solvent front to reach the top of the plate.

6. Allow the plate to dry and view it under a UV lamp. Circle the spots you see with a pencil. You may then develop your TLC plate using an iodine vapour bath. Areas where the analytes are included are stained a red/brown colour. Include images of your developed TLC plate with your report. Calculate the Rf value for each of the spots. This is the distance the spot moves up the plate divided by the distance between the bottom line and the solvent front. If you found that the spots did not move or are not separated by the solvent system, alter the ratio of ethyl acetate:hexane.

Report Requirements and Post Lab Questions -

This laboratory task will be assessed orally though a conversation with your lab demonstrator. Organise a time as soon as you are ready. We will be assessing you in 5 areas:

Your description of your separation method.

Correct identification of your Active Ingredient.

Your use and understanding of TLC to confirm the identity of the ingredient.

Your use and understanding NMR to confirm the identity of the ingredient.

Your use and understanding IR to confirm the identity of the ingredient.

This is analytical chemistry lab with virtually need help for analysis of IR, NMR and TLC to determine the 3 unknown ingredients of the tablet.

Attachment:- Experiment - Ingredient of an Analgesic.rar