4103FSBMOL - Lecture 7 - Heavy Metal Detection. Flashcards
What are the properties of Heavy Metals?
- They have high densities.
- They are persistent in the environement.
- They can’t degrade or be destroyed.
How many heavy metals are there? Can you name a few examples?
There are 23 heavy metals: antimony, arsenic, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, gold, iron, lead, manganese, mercury, nickel, platinum, silver, tellurium, thallium, tin, uranium, vanadium, and zinc.
How can Heavy metals get into the body?
- Ingestion (food and drink).
- Inhalation.
Finish the quote: “Some heavy metals are essential to the body. But at a high concentration they lead to ____________”.
Give examples.
Poisoning.
Zinc and Selenium.
What are the 5 heavy metal elements which are toxic to the body?
Mercury, Cadmium, Chromium, Lead and Arsenic.
How is Mercury toxic to the body?
It is absorbed quickly and can cause damage to the nerves, kidney, stomach, intestines and DNA.
How is Cadmium toxic to the body?
It can cause damage to the skeletal, cardiovascular, nervous and respiratory systems.
How is Chromium toxic to the body?
It can cause Respiratory issues, lug cancer, kidney and liver damage, nose bleeds and upset stomach’s.
How is Lead toxic to the body?
It can cause damage to the Liver, kidney, brain and bones.
How is Arsenic toxic to the body?
It can cause Gastrointestinal issues, problems with the nervous system and issues with DNA.
What does AAS stand for?
Atomic Absorption Spectroscopy.
What is Atomic Absorption Spectroscopy used for?
The detection of metals and metalloids. It is reliable and sensitive and can be used quantitatively - can quantify a concentration of an element.
Metalloid - a chemical element which has properties that are a mixture of, those of metals and nonmetals
What is the Sensitivity of AAS?
It works in ppb (parts per billion).
How many different elements can AAS analyse?
Over 62 different elements.
What does AAS measure?
The amount of emission given back after absorption.
In AAS, is Energy proportional or inversely proportional to the Wavelength?
Inversely Proportional.
Are AAS systems more stable at higher or lower energy?
They are more stable at a lower energy (ground state). Even in the flame, most of the atoms will be in their lowest energy state.
Is AAS a single or multi element technique?
Single-element. Separate measurements must be made if more than one metal is to be determined.
What are the principles of AAS?
- Free atoms (prepared in a solution) that are gas generated in an atomiser can absorb radiation at a specific frequency (An atomiser converts a liquid into a gas).
- AAS quantifies absorption of ground state atoms in the gaseous state.
- The atoms absorb UV or visible light and make transition to higher electronic energy levels.
- The analyte concentration is determined from the amount of absorption (amount absorbed is directly proportional to the concentration - beer lambert’s law).
- Instrument is calibrated with standards of known concentration (can’t go from zero).
What is AAS based off?
It is based on the properties of specific metal atoms to absorb specific wavelength of light. The electronics will measure light attenuation and convert those readings to the actual metal concentration of the sample.
What are the steps for Atomisation to turn your solution of analyte into atomic ions?
- Nebulization.
- Desolvation.
- Volatilisation.
- Dissociation (reversible).
- Ionisation (reversible).
- Excitation.
How does a Nebulizer work in AAS?
A nebulizer uses a flame oxidant gas to draw a solution into the nebulizer through a capillary tube. The solution is then accelerated through a narrow tube, which creates a fine spray of droplets called an aerosol.
How does Desolvation work in AAS?
The solvent is evaporated, resulting in dry nanoparticles of the sample remaining.
How does Volatilisation work in AAS?
The particles are converted to the gaseous phase by being volatised/ vapourised.