CHROMATOGRAPHY

What are my objectives while studying this topic?


By studying this topic you’ll learn about chromatography, colorimetry, and group work skills.


Why is this important?


You will see that chromatography is very important to biotechnology. It is a process which can separate complex mixtures with great precision. Even very similar components, such as proteins that may only vary by a single amino acid, can be separated with chromatography. In fact, this process can purify any soluble or volatile substance if the right adsorbent material, carrier fluid, and operating conditions are used. Furthermore, chromatography can be used to separate delicate products because it performs under conditions which are not typically severe.


You will also be looking at a new method of analysis called colorimetry. Colorimetry is the science of measuring and describing colours in numbers, and it is essential for the colour reproduction industry.


More importantly, you will carry out group work. Okay, so you’ve worked in groups since you first started school, but this is different. You will all have different roles in your small groups and you'll have to make sure you work well together as a team. This is really important in the workplace and it will give you a good idea of how it works in the real world.


Can I get an introduction to this topic?


Yes, why not have a look at the following clip:



So, let’s get to it: what are chromatography and colorimetry?


Chromatography is a method for analysing complex mixtures (such as ink) by separating them into the chemicals from which they are made. Components are distributed between two phases, one of which is stationary (stationary phase) while the other (the mobile phase) moves in a definite direction. Chromatography is used to separate and identify all sorts of substances in forensic police work. For example, you can detect drugs ranging from narcotics to aspirin in samples of urine and blood.


Type of Chromatography

How it is used in the real world

What is it?

Liquid Chromatography

test water samples to look for pollution,

Used to analyze metal ions and organic compounds in solutions. It uses liquids which may incorporate hydrophilic, insoluble molecules.

Gas Chromatography

detect bombs in airports, identify and quantify such drugs as alcohol, used in forensics to compare fibres found on a victim

Used to analyze volatile gases. Helium is used to move the gaseous mixture through a column of absorbent material.

Thin-Layer
Chromatography

detecting pesticide or insecticide residues in food, also used in forensics to analyze the dye composition of fibers

Uses an absorbent material on flat glass plates. This is a simple and rapid method to check the purity of the organic compound

Paper Chromatography

separating amino acids and anions, RNA fingerprinting, separating and testing histamines, antibiotics

The most common type of chromatography. The paper is the stationary phase. This uses capillary action to pull the solutes up through the paper and separate the solutes.


Chromatography 1

Colorimetry is the science that describes colours in numbers, or provides a physical colour match using a variety of measurement instruments. It creates standards by which to measure colour, using mathematical techniques and software to ensure reliability across media, allow accurate colour mixing, and to develop colour optimisation.


ReflCurve

Two spectral reflectance curves. The object in question reflects light with shorter wavelengths while absorbing those in others, lending it a blue appearance.


What will I be expected to be able to do after studying chromatography?


  • Know the scientific principles of chromatography

  • Describe two applications in which chromatography can be used

  • Explain the meaning of the mobile and stationary phases in chromatography

  • Be able to prepare a sample for chromatographic analysis

  • Separate a mixture using a simple chromatographic technique

  • Produce a comprehensive risk assessment for the procedure

  • Use Rf values to process and interpret the results of an investigation


What will I be expected to be able to do after studying Colorimetry?


  • Know the scientific principles of colorimetry

  • Describe two applications in which colorimetry will be used, one using simple colour change and the other using light absorption

  • Be able to prepare a sample for colorimetric analysis

  • Follow a standard procedure to calibrate and use a colorimeter to determine the concentration of a solution

  • Produce a comprehensive risk assessment for the procedure

  • Process and interpret results to determine the concentration of a solution


Once you have studied both methods and carried out your practical work and analysis, you will be expected to present your information to the rest of the class, telling them what you have learnt. You will do this in the groups that you worked in whilst discovering the information you needed to.


What are the key words to learn and use?


  • Mobile phase

  • Stationary phase

  • Rf value

  • Calibration

  • Absorption

  • Transmittance


How long will this topic take to study?


On average you’ll be looking at about six hours of study time.


What are the main activities on this topic?


In groups, research scientific principles behind chromatography to develop your understanding of:


  • Mobile and stationary phase in both thin layer and paper chromatography

  • Rf values. How to use them to analyse and interpret results


Experiment!


Demonstrate your learning by carrying out an investigation, either using paper or thin layer chromatography. Ideas and standard procedures are available from the following sites:




You’ll also need to research scientific principles behind Colorimetry. In particular, you’ll need to show knowledge of the following:


  • That light passes through a sample solution in a colorimeter. The colorimeter is calibrated by a reference sample (usually distilled water), so that the percentage of radiation absorbed and transmitted by the test sample can be measured.

  • That coloured filters are used so that a narrow band of visible radiation is absorbed and/or transmitted by the test sample. The absorption/transmittance by the test sample is proportional to the concentration of the test sample.

  • That a calibration curve is obtained by placing samples of known concentrations in the colorimeter and measuring the absorption and/or transmittance. The calibration curve can then be used to find the concentration of the test sample.


Experiment!


Ideas for investigations and limited information on the uses of colorimetric techniques can be found on the following sites:





Portfolio Activity


You can provide the following information in any way you choose. For example, you can produce a PowerPoint, posters or videos. You may want to show the class how you carried out your investigations.


For your group presentation, you need to produce and present a comprehensive risk assessment for the investigation. You also need to show:


  • That you can follow a standard procedure

  • That you can analyse and interpret results

  • How and why you prepared your sample for chromatographical/colorimetric analysis

  • How effective your investigation was and how good the technique is at doing what you wanted it to do


Use the Exemplar Risk Assessment Form



When the presentations have been completed you will have to write a report on the performance of your group - this will be part of your assessment on this topic.


You will need to write about the following:


  • How effective do you think the group was at decision-making

  • Did discussions of issues take place in order to reach agreement?

  • Did everybody contribute in a positive way to the work of the group?

  • Were tasks completed on time?

  • The quality of the presentation and visual aids


NOTE! You will also be assessed on your evaluation of whether your group worked as a team.


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