C3bL9 Modern Instrumental Methods
Key Words
Accurate - determining a number to a very small fraction.
Analysis - finding out what chemicals there are in a sample and how much of each chemical there is.
Identify - recognise and name
Sample - a small amount taken from a larger amount
Sensitive - something that detects a very small change.
Spectroscopy - studying the radiation given off by very hot samples to identify chemical patterns.
Spectrum - colours of the rainbow.
Grade E
Nowadays the analysis of chemical samples is a lot easier than it was. In the old days, skilled analytical chemists would spend hours with highly expensive glassware analysing samples, a job which can be done much more quickly with highly expensive machines. The techniques available today include:
- Atomic absorption spectroscopy;
- Infra red spectroscopy;
- Ultraviolet spectroscopy;
- Gas liquid chromatography;
- High pressure liquid chromatography.
All these techniques are more accurate, more sensitive, and require smaller samples than traditional methods.
Grade C (Higher Tier only)
| Technique | How it works |
| Atomic absorption spectroscopy | White light is made up of a spectrum. Samples of substances absorb certain colours, but not others. The pattern is distinctive for each element. The amount of light absorbed reflects the amount of of substance in the sample |
| Infra red spectroscopy | Bonds of different types absorb different wavelengths of infra red in a distinctive pattern than can be picked up by sensitive detectors and interpreted by a computer. |
| UV spectroscopy | The concentration of nitrate ions can be measured using UV spectroscopy |
Steel is an alloy of iron and carbon, and other metals. Other metals like chromium are mixed in to make specialist steels. The correct mix is important, otherwise the steel would be quite useless.
The furnaces in which these steels are made are very expensive to run, so it is important that the analysis is done quickly The amounts of each metal are worked out within one hour, and the quantity adjusted.
Grade A
Modern instrumental techniques are used widely in forensic science. It is vital that the results are accurate and reliable, since they will form the basis of criminal evidence which could send a person to prison for years. The evidence has to prove the case "beyond reasonable doubt". The worst thing that could happen is that an innocent person is punished for a crime they did not commit.