Chemical analysis as part of Quality Control Overview Learn how analytical chemistry techniques such as chromatography and volumetric analysis can be used to control the quality of products produced in an industrial process.

After completing this lesson you should be able to : In chromatography, differences in the polarity and/or size of molecules are exploited to separate the components present within a mixture. Learners are not required to know the details of any specific chromatographic method or experiment. Depending on the type of chromatography in use, the identity of a component can be indicated either by the distance it has travelled or by the time it has taken to travel through the apparatus (retention time). The results of a chromatography experiment can sometimes be presented graphically showing an indication of the quantity of substance present on the y-axis and retention time on the x-axis.

Chromatography Chromatography is one technique widely used for analysis Chromatography derives from the Greek word ‘Chroma’ meaning colour and ‘graphia’ to mean writing. COPY

Chromatography Separation depends on the equilibrium between 2 phases – a mobile phase (shoppers) – a stationary phase ( shops) COPY

Paper chromatography Stationary phase: paper Mobile phase : solvent Substances that are more soluble in the solvent travel further Substances that have more of an affinity for the paper (stationary phase) travel less far COPY

To Affinity… and beyond! Lets go shopping.. We are all on a train going to Glasgow Central. When we get off the train we all have a different ‘affinity’ to different shops. Some will go to Costa, some to the Tie Rack and some to WH Smith. It is how we, as the mobile phase, separate out on the stationary phase, Glasgow Central.

To Affinity… and beyond! Short retention time Long retention time The girls in 4 th year approve of this analogy!

Chromatography Indigo ink is a mixture of dyes (liquids) Solvent As the solvent travels up the paper the different liquids travel different distances Indigo ink contains yellow and green dyes – the mixture of inks has been seperated

Calculating Rf. COPY

Paper Stationary phase – solid, liquid supported on a solid i.e. uniform absorbent paper. Mobile phase – liquid or gas. Common use – separating ball point pen inks. COPY Chromatography simulation

Thin layer chromatography Stationary phase: glass or Al supports thin layer of cellulose or silica Mobile phase : solvent TLC quicker and prevents spots spreading Fluorescent dye can be incorporated to enable spots to be located by UV COPY

Thin Layer Stationary phase – silica/alumina backed metal/plastic/glass (can include UV plates) Mobile phase – solvent or a mixture of solvents. Common use – cannabis analysis and amino acid separation. COPY

Column chromatography The column is packed with inert material Substances take a different time to travel through the column according to their relative affinity for the solvent and the column material Each substance has a specific retention time that can be used to identify it. COPY

Column olumnChrom.htmlhttp://chemsite.lsrhs.net/FlashMedia/html/c olumnChrom.html Stationary phase – usually silica. Mobile phase – eluent and sample. Common use – separating food dyes. COPY

Gas Liquid chromatography Widely used in many industries Locally used by Diageo to test every mash produced by a distillery and every batch of alcohol produced Ensures the distillery is converting as much sugar to alcohol as possible Checks for impurities in the whisky COPY

Gas-Liquid Chromatography Stationary: High bp liquid held on an inert powdered support material, packed into a coiled column in an oven! Mobile phase : inert gas eg Helium or nitrogen Heat vaporises sample, carried by gas through hot column COPY

Gas Liquid chromatography

GLC cont Rate of travel through column depends on relative affinity for gas or inert material As substance emerged, analysed by detector, producing a graph Identification is by ‘retention time’ Area of the graph under peak is directly related to the amount of a particular compound COPY

Gas column Stationary phase- the column which contains a liquid stationary phase. Mobile phase – flow of inert gas. Usually Ne, Ar, N 2 Common use – drink driving – breath test analysis. COPY

GC Chromatograms

Retention Time The retention time of a solute is taken as the elapsed time between the time of injection of a solute and the time of elution of the peak maximum of that solute. COPY

Identification The Retention times of known compounds can been measured and recorded in a data base The Retention times of substances in the sample can then be compared to the data base and identified COPY

Chromatography is used to identify drugs in urine samples taken from athletes. The mixture of liquids in the urine is injected, samples of known drugs have already been analysed. Steroid A takes 18mins 50 sec to pass through the chromatography machine. Has the athlete tested below been using Steroid A? COPY

Chemical analysis Analaysis is very important in industry for quality control purposes Checking for contaminants Checking the level of product e.g alcohol in whisky, aspirin in tablets etc COPY

Analysis Analysis is widely carried out for a range of applications. A few examples are: 1. soil analysis 2. samples of blood, urine etc in health 3. Water purification analysis 4. swimming pools etc 5. environmental health COPY

Variety is the spice of life! Column Chromatography Paper Chromatography Ion Exchange Thin Layer Liquid Chromatography Gas Chromatography High Performance Liquid Chromatography Gel Permeation COPY