additives may be added to food and food scientists can analyse the food and identify the additives, modern instruments provide fast, accurate and sensitive ways of analyzing chemical substances,
1 of 6
Instumental Methods
Advantages:
onky need a small amount of the sample
dosnt use toxic methods
quick
sensitive
accurate
reliable
Diadvantages:
machines need energy to run
equipment is expensive
traind chemists are needed to analize results
Uses:
forensic
health
environmental
2 of 6
Paper Chromatograpghy
used for dyes and pigments
dots of single dyes are placed alongside a dot of unknown mixture on a piece of chromatograghy paper
placed in a solvent
solvent seeps up the paper, taking the dyes with it
dyes form spots in different places
patten of the singles dydes can be compared to that of the mixture
3 of 6
Gas Chromatography
used in analytical labs
drug testing
moblie phase is inert gas
gas is used to carry the substance through a column
substance travels through the tube at different speeds, so they are seperated
some substances are more attracted to the matrix than others - take longer to react
retention time - time taken to reach the detector
data plotted on a graph - the number of the peaks show the number of different compounds in the sample & the position of the peaks shows the retention time of each substance
4 of 6
Mass Spectrometry
gas chromatography linked to a mass spectrometre = GC-MS
identifys the substance leaving the column v. accuratly
the mass spectrometer can be used to find the relative molecular mass of a compound from its molecular ion peak
molecular ion peak - found as the last peak on the right as you look at the mass spectrum.
5 of 6
Key Points
compounds in a mixture can be separated using gas chromatography
once seperated, compounds can be identified using a mass spectrometer
the mass spectrometer can be used to find the relative molecular mass of a compound from its molecular ion peak (found as the last peack on the right)
Comments
No comments have yet been made