Analysing Substances
- Created by: Katie
- Created on: 20-05-13 16:35
View mindmap
- Analysing Substances
- Chromatography - Paper
- E numbers - a number assigned to a food additive that has been approved for use in Europe. It is displayed on food packaging as it is used to preserve food.
- It works due to some compounds in a mixtue dissolving easier than others in particular solvents.
- Solubility determines how far they travel across the paper.
- Additives may be added to foood in orfer to improve is appearance, taste or how long it lasts
- Instrumental Methods
- Machines are used to analyse products or special chemical products instead of humans.
- Advantages
- Accurate and sensitive
- Quicker
- It enables very small substances to be analysed
- Disadvantages
- Expensive
- Takes special training in order to be able to use
- Can only be interpreted in comparison with data from unknown substances
- Uses
- Analysing priducs
- Health Care
- Fighting pollution
- Mass Spectrometry
- Compounds can be identified using this method.
- The first step is vapourisation - this is where a sampe is 'injected' into a high temperature chamber where it is vapourised. The particles in the vapour are sucked through the mass spectrometer by a pump.
- Ionisation - electrons are fired at the sample to ionise it to form positive ions.
- Acceleration - a strong electric field accelerates the ions forward.
- The ions pass through a velocity sector, where electrical ad magnetic fields ensure that all the particles passing through have the same velocity.
- Deflection - the charged particles pass through a uniform magnetic firls which deflects them sideways. The heavier the particle, the less it is deflected.
- The ions pass through a velocity sector, where electrical ad magnetic fields ensure that all the particles passing through have the same velocity.
- Acceleration - a strong electric field accelerates the ions forward.
- Ionisation - electrons are fired at the sample to ionise it to form positive ions.
- Gas Chromatography
- Compounds in a mixture can be sperated using this mixture.
- First the sample mixture is vaporised.
- Second, the 'carrier' gas moves the vapour through the coiled column.
- The compounds in the sample have differet attractions to the material in the column. The compounds with stronger attractions will take longer to get through the column.
- We say they have a longer retention time. The compounds with weak attractions to the material in the column leaft first - shorter retention time.
- Retention time - the time it takes a component in a mixture t pass through the column in gas chromatography.
- Different compounds have different retention times due to how strong or weak the attractions are towards the material.
- Retention time - the time it takes a component in a mixture t pass through the column in gas chromatography.
- We say they have a longer retention time. The compounds with weak attractions to the material in the column leaft first - shorter retention time.
- The compounds in the sample have differet attractions to the material in the column. The compounds with stronger attractions will take longer to get through the column.
- Second, the 'carrier' gas moves the vapour through the coiled column.
- Chromatography - Paper
Comments
No comments have yet been made