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