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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. 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 Quantitative – amount of pesticide residue found on crops Physical properties: colour, mass, solubility, melting/boiling point Chemical properties: reactions with acid/base, oxidation
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TechniquePhysical or Chemical PropertyExamples of Analysis Analysis by Mass Gravimetric AnalysisMass 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 TitrationsNeutralisations reactions by acid or baseConcentration of ammonia in window cleaner Redox TitrationReactant as an oxidant or reductantConcentration 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 SpectrometryMass/charge ratio of ionised compoundIdentification of lead isotope ratios in meteors
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