Year 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.

 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.

 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

 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.

 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

 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

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