Year 12 Chemistry Unit 3 – AOS 1 Chemical Analysis.

Year 12 Chemistry

Unit 3 – AOS 1 Chemical Analysis

Quantitative and Qualitative Analysis

• Qualitative Analysis: - Identification of chemicals present

• Quantitative Analysis: - Identification of how much of each chemical is present

Physical Properties

• Physical Properties: - Colour, mass, solubility, melting point, response to electromagnetic radiation.

• Chemical Properties: - reactions with acids, bases, oxidants or reductants, precipitates.

• Gas Chromatography – Nick & Arafath• High Performance Liquid Chromatography – Thilag

& Stephen• UV-Visible Spectroscopy – Pricilla, Maria, Samira • Atomic Absorption Spectroscopy – Mae & Claire• Infra-Red Spectroscopy – Sandip, Amy & Jocelyn• Nuclear Magnetic Resonance Spectroscopy – Sahil

& James• Mass Spectroscopy– Sandip, Amy & Jocelyn

Types of Analysis

Gas Chromatography (GC) Description

Stationary Phase: Gel coated solidMobile Phase: GasA sample is injected into a column with a carrier gas. The components of the sample travel through the column at different rates to a flame.

Basic TheoryComponents of a sample move at different rates through a column. Qualitative results based on rt.. Once the components have been separated a quantitative results can be obtained based on the flame responds to the material.

Gas Chromatography (GC)Major Uses

Provides both qualitative and quantitative analysis of compounds with a molar mass of less than 300. Compounds must be easily vapourised, without decomposing. Used for analysis of blood and urine for the presence of drugs

Typical Analyte:Low molecular mass compounds

Typical Sample:Foods, drugs, biological samples

Advantages:Highly sensitive and precise

Disadvantages:Moderately expensive

Gas Chromatography

High Performance Liquid Chromatography (HPLC)

DescriptionStationary Phase: Gel covered solidMobile Phase: SolventA sample is injected into a column under high pressure, The components of the sample travel through the column at different rates.

Basic TheoryComponents of a sample move at different rates through a column. Qualitative results based on rt..

High Performance Liquid Chromatography (HPLC)

Major UsesProvides both qualitative and quantitative analysis of large molecular substances. Ideal for identifying compounds that do not vaporise or will decompose. Used for the analysis of proteins and organic compounds.

Typical Analyte:Medium to high mass organic compounds

Typical Sample:Foods, drugs, biological samples

Advantages:High sensitivity and precision

Disadvantages: Moderately expensive

High Performance Liquid Chromatography (HPLC)

Ultra-Violet Visible Spectroscopy Description

UV light of a complimentary colour to the colour of the substance tested is passed through the substance to a receiver.

Basic TheoryLight is absorbed by some molecules. The amount of light absorbed is proportional to concentration of the molecule, allowing in quantitative results being obtained.

Ultra-Violet Visible SpectroscopyMajor Uses

Generally used as a quantitative analysis to determine the concentration of organic compounds and metal ions in urine, blood, plastics or water. Can be used as qualitative using the unique spectra as a fingerprint

Typical Analyte:Low mass organic compounds

Typical Sample:Liquid and gas samples

Advantages:Simple to operate

Disadvantages:Not suitable for low concentrations

Ultra-Violet Visible Spectroscopy

Atomic Absorption Spectroscopy (AAS)

DescriptionA light of a specific wavelength is passed through a flame which contains a vaporised sample. The light passes through a wavelength selector to a detector

Basic TheoryWhen a metal atom absorbs energy its electrons will jump to higher energy states. The wavelength of the light absorbed identifies the element, the intensity of the light absorbed identifies the concentration.

Atomic Absorption Spectroscopy (AAS)

Major UsesUsed in quantitative analysis to determine the concentration of metals in blood, urine, air, soil, water and foods. May by used qualitatively to determine the presence of metals.

Typical Analyte:Metals

Typical Sample:Low viscosity solutions

Advantages:Highly sensitive and precise

Disadvantages:Moderately expensive

Atomic Absorption Spectroscopy (AAS)

Infrared Spectroscopy (IR)

DescriptionInfrared light is passed through a sample to a detector. The percentage absorption and wavelength is measured, resulting ina unique IR spectrum.

Basic TheoryFunctional groups absorb infrared light at specific wavelengths. Based on the was the sample responds to IR light the functional groups and overall structure can be identified

Infrared Spectroscopy (IR)Major Uses

Used for qualitative analysis to determine the types of bonds and functional groups present.

Typical Analyte:Organic molecules

Typical Sample:Solids, liquids or gases

Advantages:Huge range of analytes

Disadvantages:Moderately expensive

Infrared Spectroscopy (IR)

Nuclear Magnetic Resonance Spectroscopy (NMR)

DescriptionA sample is placed in a test tube that spins between a powerful magnet. A radio transmitter coil produces a short powerful pulse of radio waves, a radio then detects the radio frequencies emitted from the nuclei as they relax to a lower energy level

Basic TheoryAny atom with an odd number of protons or neutrons will absorb energy, resulting in being in a state of resonance. Atoms in different configurations result in different energy shifts. The resulting shift in energy can be used to identify the configuration of the atom.

Nuclear Magnetic Resonance Spectroscopy (NMR)

Major UsesUsed in qualitative analysis to provide information in the determination of the structure of the carbon-hydrogen backbone of organic compounds

Typical Analyte:Organic molecules

Typical Sample:Liquid or solids

Advantages:Highly sensitive and precise

Disadvantages:Very expensive

Nuclear Magnetic Resonance Spectroscopy (NMR)

Mass SpectroscopyDescription

A gaseous sample is injected into the chamber, where it is ionised. Positive ions are accelerated in a magnetic field. Ions move in a curved path depending on their mass/charge ratio. The detector measures the relative abundance of each m/e ratio.

Basic TheoryCharged particles move in a curved path relative to the mass/charge ratio. Using an ion collector we can detect the amount of ions in each mass/charge ratio. The mass/charge ratios can be compared to a book of data to identify fragments.

Mass SpectroscopyMajor Uses

Used in qualitative analysis to determine the structure and identity of a compound. Can be used in quantitative analysis as a detector for Atomic Emissions Spectroscopy, Gas Chromatography and Liquid Chromatography

Typical Analyte:Any elements/compounds that can be volatised

Typical Sample:Anything that can be volatised

Advantages:Highly sensitive and precise for wide range of analytes

Disadvantages:Expensive and requires training to operate

Mass Spectroscopy