How does a flame photometer work?
A flame photometer is an analytical tool that uses emission spectroscopy. It has parts for burning gas and flame, an optical part, a photoelectric converter, and a part for detecting and writing down what it sees. The flame’s heat energy is used to make the atoms of a certain element give off light, and an instrument can measure how strong that light is. Then, this can be used to figure out what a certain part of the material is about.
Things that affect how sensitive a flame spectrometer is
1) Analysis line
When there are many analytical lines for each element, the resonance line is usually the most sensitive and is often used as the analytical line. However, this sensitive line should be chosen when measuring samples with higher concentrations. For example, the analysis line for measuring sodium is a = 589.0nm, and when the concentration is higher, the analysis line is a = 330.0nm.
The type and state of the flame are very important to the sensitivity, and different flames should be chosen based on the properties of the thing being measured. At the moment, flames can be split into three types: air-hydrogen flame, air-acetylene flame, and nitric oxide-acetylene flame. The air-hydrogen flame has a low flame temperature and is used to find elements that easily break apart in the flame, like arsenic and selenium.
The air-acetylene flame is a medium-temperature flame, and it is used to find elements that are hard to break apart in the flame, like magnesium and calcium, copper, zinc, lead, manganese, etc. The nitric oxide-acetylene flame is a high-temperature flame, and it is Depending on its state, the flame is called a lean flame, a stoichiometric flame, or a rich flame. When too much oxidant is used, the flame is said to be “lean.”
The flame temperature is low since a lot of cold oxidant takes away the heat in the flame. This flame is good for finding alkali metal elements because there is enough oxidant, the combustion is complete, and the flame has an oxidizing atmosphere. The stoichiometric flame is a flame that burns with the right amount of fuel and oxygen based on the stoichiometric relationship.
It has a high temperature, less interference, is stable, and has a low background. Aside from alkali metals and easily formed refractory oxides, alkali metals and easily formed refractory oxides are the most common elements. People often use this flame. A “rich flame” is one that burns more fuel than it needs to. The flame has a strong reducing atmosphere because it isn’t burning all the way. This flame has reducing properties and can be used to find elements that are more likely to form refractory oxides, such as molybdenum, rare earth elements, etc.
When the element being measured doesn’t have any interference lines next to it, like potassium, sodium, etc., a larger slit can be used. When the element being measured, like calcium, iron, magnesium, etc., has interference lines close together, a smaller slit can be used.
4) Lamp voltage
Most of the light sources used in flame atomic absorption spectrophotometers are hollow cathode lamps, which only require one lamp current to work. How much light a lamp gives off depends on how much current it has. Increasing the lamp current within a certain range can make the light brighter, but it also makes the lamp less stable and lowers the signal-to-noise ratio.
This makes the instrument less sensitive. If the lamp current is too high, the lamp will corrode on its own, which will shorten its useful life. It will also discharge in an odd way, which will make the lamp’s light intensity change. On the other hand, lowering the lamp current within a certain range can lower the intensity of the light and make the instrument more sensitive, but it also lowers the stability of the lamp and the signal-to-noise ratio.
If the lamp’s current is too low, the lamp’s radiation will be less strong, which will cause the stability and signal-to-noise ratio to drop so much that it can’t be used. So, in specific detection work, if the concentration of the sample being tested is high, use a larger lamp current to get better stability. If the concentration of the sample being tested is low, use the premise of making sure the stability meets the requirements. Lower the lamp current to make the light more sensitive.
5) How much lift
The sensitivity is affected by how much lift there is. If the lift is too high or too low, the atomizer will not be stable. Each manufacturer has a different range for how high an instrument can be lifted. Here are some ways to make the lift stronger:
(1) Increase the gas flow rate. In this way, the amount of lifting goes up when the negative pressure goes up.
(2) Cut the length of the tube used to give the injection. When you cut the length of the injection tube, the resistance of the tube goes down and the test solution flows through it faster. On the other hand, if you want to lower the lift, you can lower the flow of combustion gas or make the injection tube longer.
The atomizer’s job is to break up the test solution into tiny pieces. It is a key part of the atomic absorption spectrophotometer, and how well it works has a big effect on the sensitivity, precision, and chemical interference of the assay. The more stable the spray of the atomizer is, the smaller and more uniform the droplets, the higher the atomization efficiency, the higher the sensitivity, the better the precision, and the less chemical interference there is.
At the moment, you can adjust the atomizer by changing where the impact ball is in relation to the capillary. The inspector should adjust the atomizer so that the droplets are small and uniform and that they are spread out evenly around the impact ball. If that can’t be done, the droplets can be spread out evenly around the impact ball.
7) Burner position
Adjust the height and position of the burner’s front and back so that the light beam from the hollow cathode lamp goes through the part of the flame with the most free electrons. At this time, things are at their most sensitive and stable. If you don’t need very high sensitivity, like when measuring a large amount of a test solution, you can change the angle of the burner to make it easier to see.
Stability of the flame: If the temperature of the flame is too low, the sensitivity will go down. If the temperature of the flame is too high, there will be a lot of alkali metal ionization, which will change the linear relationship of the measurement. The ratio of compressed air to combustion gas also has a big effect on how stable the flame is. Whether or not the gas pressure stays the same is another thing that affects how stable the flame is.
- The atomizer’s effect on atomization: The atomizer’s job is to break up the test solution into tiny pieces. The way it works has a big effect on the sensitivity, precision, and chemical interference of the assay. The more stable the spray of the atomizer is, the smaller and more uniform the droplets, the higher the atomization efficiency, the higher the sensitivity, the better the precision, and the less chemical interference there is.
- The quality of the filter: A good filter can reduce the effect of substances that are already there. Also, the filter should be fixed inside the flame photometer so that you don’t have to keep changing it and wearing out the device.
- Measuring Range: The flame photometer has a wide measuring range, which can reduce the sample’s dilution ratio, cut down on human error, and make the results more accurate.
What to look for in a flame photometer
There are a lot of different brands and models of flame photometers on the market, which makes it hard to choose the right one. Before we buy a flame photometer, we can compare them by looking at their parameters, how easy they are to use, and how much they cost.
- How it looks and how safe it is
There are a lot of different analytical tools in the lab, but there isn’t much room. Choose a flame photometer with a small footprint and low noise as your first option. Some flame photometers are not only beautiful to look at, but they also have a quiet air compressor built in and can detect when the flame goes out and turn off automatically, saving you space and stress.
- Device parameters
On one hand, the way it looks is nice. The parameters of the hard instruments still affect what instruments and other tools the lab buys. Examples:
1) Measuring range
The range should be as wide as possible. For the flame photometer to work, the sample may need to be diluted more than once. This could make it harder to measure accurately because of the error logarithmic amplification effect.
2) Stability of the fire
The amount of combustion gas to compressed air and whether or not the gas pressure stays the same affect how stable a flame is. A very stable flame is the only way to make sure that the measurement is sensitive and accurate.
3) Filter quality
The filters are high quality so that they don’t get messed up by other species. The filter should be fixed inside the flame photometer so that it doesn’t have to be changed as often and wear out less quickly.
4) The effect of atomization
How well the nebulizer works has a big effect on the sensitivity, precision, and chemical interference of the assay. A good flame photometer atomizer has a steady spray, small droplets that are all the same size, high sensitivity, and good accuracy.
5) Drift amount: During the detection process, data that keeps changing will make it hard to judge how reliable the data is. A flame photometer that is stable should make sure that the 30 minute drift is as small as possible.
Along with parameters, the ease of using an instrument also affects how the user feels about it. In addition to a simple, easy-to-understand interface and screen display, there are a few other things to think about when it comes to how easy it is to use.
1) Reading Style
If the flame photometer‘s continuous reading mode can read measured values 20 times per second and automatically calculate the average value of the read data, it will be easier to use and less likely that random errors will happen. With the automatic concentration reading feature, the experimenter doesn’t have to figure out the regression equation or draw the working curve. Instead, they can just read the concentration value of the sample liquid directly from the flame photometer.
2) Detection method
Some flame photometers can find a lot of different ions at the same time. This saves a lot of time and trouble because you don’t have to change filters and calibrate each time. This is a big benefit for labs that need to take a lot of measurements.
3) Calibration function
With internal calibration, a flame photometer can save a lot of time and get rid of calibration errors caused by changes in the environment. When you need to measure for a long time, using the single-point calibration function can save you a lot of time. With the multi-ion standard calibration function, you can make sure that different ion calibrations don’t happen at the same time.
4) Report results
By connecting to the control analysis software, the flame photometer with RS232 and USB interfaces can automatically output data, curves, and concentration calculation results in the format you choose. This makes work much more efficient.
Why does the flame photometer’s sensitivity go down over time?
If the sensitivity goes down, get rid of any physical factors first. If the liquid is atomized well and the flame burns normally and the instrument has been used for a long time, the filter may be moldy or the photocell may not be able to release electrons as well as it used to. If any of the above parts are changed, the sensitivity will not change. If the increase is too big, the amplifier may be to blame.
Even though the sensitivity has been improved, it is not ideal to change the measuring amplifier’s power supply to 12V and replace the impedance converter FET and operational amplifier. To make the instrument sensitive again, a high-impedance amplifier is added to the feedback end of the amplifier.
Is a flame photometer the same thing as an atomic spectrophotometer?
The flame’s heat energy is used to excite the atoms of an element so that they give off light. The intensity of the element’s spectral energy is measured by an instrument to figure out how much of that element is in the material.
A flame photometer is the name for this kind of tool. The main components of an atomic spectrophotometer are the light source (a monochromatic sharp line radiation source), the sample atomizer, the monochromator, and the data processing system (including a photoelectric converter and corresponding detection device). There are two main kinds of atomizers: those that use a flame and those that use electricity. So, a flame photometer is a type of atomic spectrophotometer.
How are a flame photometer and a spectrophotometer different from each other?
Atomic emission is used by the flame photometer to break up the corresponding substances into tiny particles (solids are made into solutions, such as being dissolved in acid). The liquid is very hot, and the gas is excited by the discharge. The excited electrons have a high level of energy, are unstable, and will change. Back in the ground state, different atoms have different levels of electron energy, so when they change, they give off light waves of different lengths.
By looking at the waves of light, you can figure out what atoms are. In the same way, the strength of the light wave can be used to figure out what’s inside the atom. The UV-Vis spectrophotometer works on the principle of absorption. The UV region (200–400 nm) is usually used to analyze organic substances.
How is a flame atomic absorption spectrometer different from a flame photometer?
Most metal atoms are measured with a flame atomic absorption spectrometer, while Na, K, and other halogen elements are mostly measured with a flame photometer.