Analysing Substances
It is possible to detect and identify elements and compounds using instrumental methods, which are accurate, sensitive and rapid, and are particularly useful when there is only a small amount of a sample available.
Chemical analysis can be used to identify additives and paper chromatography can be used to detect and identify artificial colours in foods.
An example of an instrumental method used to identify elements and compounds is gas chromatography used in conjunction with mass spectroscopy (GC-MS).
In gas chromatography, different travel, carried by a gas, at different speeds through a column packed with a solid material, so that they become separated.
By measuring the time a substance takes to travel through the column, it is possible to identify the substance. The number of peaks on the output of the gas chromatograph shows the number of compounds present.
By linking the output from the gas chromatography column to a mass spectrometer, it can be used to identify substances leaving the end of the column. The position of the peaks on the output indicates the retention time of the substances.
The mass spectrometer can identify substances very quickly and accurately, detect very small quantities of substances and provide the relative molecular mass of each of the substances separated in the column.
The molecular ion peak indicates the molecular mass.
