Year 12 Chemistry
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An analytical technique is a method that is used
to determine the presence and concentration of a
chemical compound or chemical element. There
are a wide variety of techniques used for analysis,
from simple weighing (gravimetric) to titrations
and very advanced techniques using highly
specialized instrumentation. The most common
techniques used in analytical chemistry are:
Titrations
Spectroscopy
Chromatography
Mass spectrometry
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A titration is a common laboratory method
of quantitative chemical analysis that is
used to determine the unknown
concentration of a known reactant. Because
volume measurements play a key role in
titration, it is also known as volumetric
analysis.
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Examples of common titrations in industry:
Karl Fischer titration: a method to analyse
trace amounts of water in a substance.
Iodine number: a redox titration with colour
indication which indicates the amount of
unsaturated fatty acids present.
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Spectrometry is the spectroscopic technique used
to assess the concentration or amount of a given
chemical (atomic, molecular, or ionic) species. In
this case, the instrument that performs such
measurements is a spectrometer,
spectrophotometer, or spectrograph.
Emission spectroscopy uses the range of
electromagnetic spectra in which a substance
radiates (emits). The substance first must absorb
energy.
Absorption spectroscopy uses the range of the
electromagnetic spectra in which a substance
absorbs. This includes atomic absorption
spectroscopy and various molecular techniques,
such as infrared and ultraviolet-visible.
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Chromatography is the collective term for a
set of laboratory techniques for the
separation of mixtures
Gas Chromatography
Liquid Chromatography
Column Chromatography
Paper Chromatography :
Thin Layer Chromatography
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Mass spectrometry is an analytical technique for
the determination of the elemental composition
of a sample or molecule. It is also used for
clarifying the chemical structures of molecules,
such as peptides and other chemical compounds.
The technique has both qualitative and
quantitative uses. These include identifying
unknown compounds, determining the isotopic
composition of elements in a molecule as well as
determining the structure of a compound by
observing its fragmentation. Another use
includes quantifying the amount of a compound
in a sample.
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Monitoring the environment
Transport safety – analysis of fuel source
Wine making
Food manufacturing - not for just labelled
processed products, also for fresh fruit & fish
Forensic science
Diagnosis of disease
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Qualitative – types of chemicals present in
plant extracts
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Quantitative – amount of pesticide residue
found on crops
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Physical properties: colour, mass, solubility,
melting/boiling point
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Chemical properties: reactions with
acid/base, oxidation
Technique
Physical or Chemical Property
Examples of Analysis
Mass of chemical, isolated from a mixture or
precipitated in a reaction
Percentage of water in wheat stored in a silo.
Concentration of salt in a jar of baby food
Acid-Base Titrations
Neutralisations reactions by acid or base
Concentration of ammonia in window cleaner
Redox Titration
Reactant as an oxidant or reductant
Concentration of hydrogen peroxide in hair
bleach.
Chromatographic Analysis
- Paper
- Thin Layer
- Gas
- High Performance Liquid
Adsorption onto a stationary phase and
solubility in a mobile phase
Analysis of codeine in a tablet
Concentration of alcohol in the blood
Spectroscopic Analysis
-Flame Tests
-Atomic Emission
-Atomic Absorption
-Ultraviolet-Visible
-Infrared
-Nuclear Magnetic Resonance
Absorption or emission of part of the
electromagnetic spectrum
Monitoring level of calcium in the blood
Mass Spectrometry
Mass/charge ratio of ionised compound
Identification of lead isotope ratios in meteors
Analysis by Mass
Gravimetric Analysis
Volumetric Analysis