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Identifying background radiation sources in flame photometry

Sources of background interferences are those that emit either light or electronic interference.

These are usually cancelled out from the collected signal source via calibration of a blank, or via the use of grounding to eliminate the stray electrons present in circuitry during voltage measurement.

Types of interference that affect the light emitted from the sample could be atmospheric effects, background radiation, entropy-based random emissions and also stray light sources.


Background radiation

What are atmospheric effects?

Atmospheric effects have a number of impacts on the solar radiation at the surface of the Earth.

Such effects include oxygen and CO2 content.

This affects the combustion of the fuel and the ambient pressure that affects the rate at which combustion occurs, as well as the ambient temperature.


What is background radiation?

Identifying background radiation is important due to the fact that background radiation that affects the detection of concentrations of ions in a sample during photometry is usually a secondary radiation from cosmic radiation.

Cosmic radiation bombards the Earth's atmosphere with positively-charged ions ranging from protons up to iron (by atomic weight).

This then converts to secondary radiation, including electrons alongside a smattering of other particulate and wave type matter, which then exist over the Earth’s surface.

These electrons can be detected by a voltmeter, which detects the voltage emitted from the photodiode array. This is cancelled out with a blank calibration.


What is grounding?

Grounding is a technique that electrical engineers utilise to form a common return path for electric current or directly connect the current to the Earth.

This limits sources which could be picked up by the voltmeter and confused with actual current detected from the photodiode array, from the photon packets emitted from the excitation of the analyte.


What is stray light?

Stray light is another source of background radiation emitted from the sun in the form of photons.

In the sun, elements range from hydrogen up to iron. Therefore, included in the sun's chemical makeup would be quantities of sodium, potassium, calcium, barium and lithium.

All of these would be superheated and constantly radiating photons from excitation due to the sun's extreme temperatures.

This means the light that surrounds us is partially of the same wavelength which the photodiode arrays could detect, and is another source of interference that the blank standard cancels out via calibration.


What are entropy-based random emissions?

Entropy-based random emissions are a type of emission that are due to the absolute random nature of particle-to-particle interactions.

If a puddle of water can slowly evaporate due to this type of interaction - where water molecules of random energy levels interact some can break from the aqueous form and turn to the gaseous form - then it would be indicative that the excitation of atoms or ions could also occur due to random particle collisions.

This type of emission is totally random. However, it is very minute and should not affect the signal detected very much.

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