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Analytical TechniquesYear 12 Chemistry
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
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.
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.
Titration
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.
Spectroscopic Analysis
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
Chromatography
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.
Mass Spectrometry
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
Where are these applications used?
Qualitative – types of chemicals present in plant extracts
Quantitative – amount of pesticide residue found on crops
Physical properties: colour, mass, solubility, melting/boiling point
Chemical properties: reactions with acid/base, oxidation
What properties are examined?
Technique Physical or Chemical Property Examples of Analysis
Analysis by Mass
Gravimetric 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
Volumetric Analysis
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 tabletConcentration 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
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