Definitions Flashcards
Qualitative analysis
Determining what types of substances are present, whether the correct ingredients have been used or whether impurities are present
Quantitative analysis
As the ‘body of chemical knowledge’ increased, the emphasis was directed to determining how much of
a particular component (or group of components) is present. E.g : determining the amount of an
ingredient, the amount of an impurity or the proportion of water in a sample etc
Analyte
The subject of the analysis
Spectroscopy
amount of electromagnetic radiation absorbed or emitted at a particular wavelength
Chromatography
measuring the rate at which analytes migrate through a column containing an insoluble material
Mass spectroscopy
observing the types of molecular fragments produced after bombarding the analyte with sub-atomic particles
NMR
monitor the amount of radio energy absorbed by an analyte when placed in a magnetic field.
Accurate result
one in which systematic errors are small and the average result or measurement of a set of replicates equals, or is very close to the true result
absolute error (Ea)
Ea = Tv - r
relative error (E%)
E% = (Ea/Tv )x 100
Precise result
random errors are small and the analyst is seeking to obtain a set of very similar replicate analyses. This is often described as a high level of reproducibility
coefficient of variation (CV)
CV% = s/r x 100
How do you obtain results that are both accurate and precise
observing good laboratory practice to reduce systematic errors and by carrying out replicate analyses to reduce random errors and improve precision.
Stationary phase
One phase is retained completely by the chromatography equipment
mobile phase
is allowed to percolate through, ‘carrying’ the
sample components.
