Flame Photometry | Thermometric Sensors

VTU Chemistry

18 Nov 202305:53

Summary

TLDRFlame photometry is a technique for measuring thermal changes, particularly the emission of light from excited metal atoms in a flame. It involves the aspiration of metal compounds into a flame, where they dissociate into atoms, get excited, and emit light at specific wavelengths. The intensity of this light is proportional to the metal's concentration in the solution. The flame photometer uses a nebulizer, a burner, an optical system with a lens and filter, and a photodetector to convert the emitted light into an electrical signal. This method is widely used for qualitative and quantitative analysis of elements like sodium, potassium, and calcium in various samples, including biological fluids, plant material, water, soil extracts, cement, and glass.

Takeaways

🔍 Flame photometry is a thermometric sensor technique used for measuring thermal changes, such as temperature or flame emission, during the interaction between an analyte and a reagent.
🌡 The process involves the aspiration of compounds containing group two metals or alkali and alkaline earth metals into a flame, which leads to their dissociation into atoms.
💧 When a solution is aspirated into the flame, the solvent evaporates, leaving the salt which then vaporizes and dissociates into gaseous atoms.
🔥 The metal atoms in the gaseous state absorb heat from the flame and become excited to a higher energy level, then return to their ground state by emitting light radiation.
📏 The intensity of the emitted light is proportional to the concentration of the solution and the number of atoms in the excited state.
🌈 Different metals emit light at different wavelengths, for example, sodium at 589 nanometers and potassium at 766 nanometers.
🔧 The detector response (E) is measured using the expression E = K * Alpha * C, where K is a constant, Alpha is the efficiency of atomic excitation, and C is the concentration of the solution.
🧪 The flame photometer works by injecting the sample through a nebulizer, mixing it with fuel in a chamber, and then observing the flame emission after ignition.
🔭 The emitted radiation passes through a lens and filter to isolate the specific wavelength of interest, which is then detected and converted into an electrical signal by a photodetector.
🛠️ The optical system of a flame photometer includes a convex mirror and lens to focus the emitted light, a filter to isolate the wavelength, and a photodetector to convert light into an electrical signal.
🔬 Flame photometry is used for both qualitative and quantitative analysis of various materials in biological fluids, plant material, water samples, soil extracts, and even in cement and glasses for the determination of specific ions like sodium, potassium, and calcium.

Q & A

What is flame photometry?
-Flame photometry is a type of thermometric sensor used for measuring thermal changes, such as temperature changes or flame emission, during the interaction between an analyte and a reagent.
How are thermal changes in flame photometry converted into measurable signals?
-The thermal changes are converted into measurable electrical signals through the process of dissociation and excitation of atoms in the flame, which then emit light radiation.
What happens when a compound of group two metals or alkaline earth metals is aspirated into the flame?
-The compound dissociates into atoms, which then get vaporized into a gaseous state and further absorb heat from the flame, leading to the excitation of metal atoms.
How does the metal atom return to its ground state after excitation?
-The metal atom returns to its ground state by emitting energy in the form of light radiation.
Why is the intensity of emitted light radiation proportional to the concentration of the solution?
-The intensity of the emitted light radiation is proportional to the number of atoms in the excited state, which is related to the concentration of the solution fed to the flame.
What is the detector response 'e' in the context of flame photometry?
-The detector response 'e' is given by the expression e = K * Alpha * C, where K is a constant, Alpha is the efficiency of atomic excitation, and C is the concentration of the solution.
How does the emitted radiation differ for different metals?
-The emitted radiation differs for different metals due to the specific wavelengths at which each metal emits light, such as sodium at 589 nanometers and potassium at 766 nanometers.
What is the role of the nebulizer in flame photometry instrumentation?
-The nebulizer's role is to inject the sample into the flame photometer, creating a homogeneous solution that is sent into the flame at a balanced rate.
What is the function of the filter in the optical system of a flame photometer?
-The filter in the optical system allows only a particular wavelength of radiation to pass through, isolating the wavelength to be measured from the emitted radiations.
How does a photodetector contribute to flame photometry?
-The photodetector converts the emitted radiation into an electrical signal, which is then amplified and displayed, providing a measurement that is directly proportional to the intensity of the light.
What are some applications of flame photometry?
-Flame photometry is used for both qualitative and quantitative analysis, including the analysis of materials in biological fluids, plant material, determination of sodium, potassium, and calcium ions in water samples and soil extracts, and the determination of calcium ions in cement and glasses.

Outlines

00:00

🔥 Introduction to Flame Photometry

In this session, the concept of flame photometry is introduced. Flame photometry is described as a type of thermometric sensor used to measure thermal changes such as temperature variations or flame emissions during the interaction between the analyte and the reagent. These thermal changes are converted into measurable electrical signals. The process involves aspirating compounds of Group 2 metals or alkali and alkaline earth metals into the flame, leading to dissociation into atoms, vaporization, and emission of light radiation. The intensity of the emitted light is proportional to the concentration of the solution fed into the flame. Different metals emit radiation at different wavelengths, with sodium emitting at 589 nm and potassium at 766 nm. The detector response is measured using the formula E = K * α * C, where K is a constant, α is the efficiency of atomic excitation, and C is the concentration of the solution.

05:02

🔧 Instrumentation and Working of Flame Photometry

The section explains the instrumentation and working of a flame photometer. The analyte sample is injected into the flame photometer through a nebulizer, where air is applied to suck the sample. Fuel like LPG is mixed with the sample in the mixing chamber, and upon lighting the flame, processes such as solvent evaporation, salt vaporization, atom dissociation, and metal atom excitation occur, leading to flame emission. Different metals emit different radiations, which are focused through a lens onto a filter slit. The filter isolates the desired wavelength, and the photo detector converts the radiation into an electrical signal, which is amplified and displayed. The nebulizer ensures a homogeneous solution flow into the flame, and the optical system focuses the emitted light onto the filter slit. The photo detector's signal is directly proportional to the light intensity.

🌱 Applications of Flame Photometry

This paragraph outlines various applications of flame photometry. It is used for both qualitative and quantitative analysis, applicable for analyzing materials in biological fluids and plant samples. Flame photometry is also used to determine sodium, potassium, and calcium ions in water samples and soil extracts. Additionally, it is employed in the determination of calcium ions in cement, glass, and other materials. These applications highlight the versatility and importance of flame photometry in various fields.

Mindmap

Keywords

💡Flame Photometry

Flame photometry is a technique used to measure the concentration of certain elements in a sample by observing the light emitted when the sample is exposed to a flame. In the context of the video, it is a thermometric sensor that measures thermal changes, such as temperature changes or flame emission, during the interaction between the analyte and the reagent. The script describes how flame photometry is used to determine the concentration of elements like sodium and potassium by measuring the intensity of light they emit at specific wavelengths.

💡Thermometric Sensor

A thermometric sensor is a device that measures temperature or thermal changes. In the script, it is used to describe the general category of sensors that flame photometry falls under, which includes the measurement of thermal changes like temperature changes or flame emission. The video explains how these thermal changes are converted into measurable electrical signals in the process of flame photometry.

💡Analyte

An analyte is the substance being analyzed in a chemical analysis. In the context of flame photometry, the script mentions that the analyte is a compound of group two metals or alkali and alkaline earth metals that, when aspirated into the flame, dissociates into atoms. This dissociation leads to the excitation and subsequent emission of light at specific wavelengths, which is then measured.

💡Dissociation

Dissociation refers to the process where a compound breaks down into its constituent atoms or simpler molecules. In the script, it explains that when the analyte is aspirated into the flame, it undergoes dissociation, turning from a solution into gaseous state atoms, which is a crucial step for the flame photometry process to occur.

💡Excitation

Excitation in the context of flame photometry is the process where atoms absorb energy from the flame and move to a higher energy level. The script describes how the metal atoms, after being dissociated into the flame, get excited to a higher energy level and then fall back to their ground level by emitting light radiation, which is the basis for the measurement in flame photometry.

💡Emission

Emission in this context refers to the release of energy in the form of light radiation that occurs when an atom returns from an excited state to its ground state. The script explains that the intensity of the emitted light radiation is proportional to the concentration of the analyte in the solution, which is essential for the quantitative analysis performed by flame photometry.

💡Wavelength

Wavelength is the distance between two consecutive points in a wave that are in the same phase. In the script, it is mentioned that different metals emit radiation at different wavelengths, such as sodium at 589 nanometers and potassium at 766 nanometers. The flame photometer uses filters to isolate the specific wavelength of interest for the analysis.

💡Nebulizer

A nebulizer is a device that converts a liquid into a fine mist or aerosol. In the script, it is described as the component of the flame photometer that injects the sample into the flame, allowing for a homogeneous solution to be sent into the flame at a balanced rate, which is important for accurate measurements.

💡Photodetector

A photodetector is a device that converts light into an electrical signal. The script explains that in flame photometry, the emitted radiation is received by the photodetector, which then converts it into an electrical signal. This signal is amplified and displayed, providing a measurable output that is proportional to the intensity of the light.

💡Quantitative Analysis

Quantitative analysis is the process of determining the amount or concentration of a substance within a sample. The script mentions that flame photometry is used for both qualitative and quantitative analysis, particularly for determining the concentration of elements like sodium, potassium, and calcium in various materials such as biological fluids, plant material, water samples, and soil extracts.

💡Qualitative Analysis

Qualitative analysis is the process of identifying the presence or absence of certain substances in a sample. Although the script primarily focuses on quantitative analysis, it also mentions that flame photometry can be used for qualitative analysis, which helps in identifying the different materials present in samples like biological fluids and plant material.

Highlights

Flame photometry is a thermometric sensor technique for measuring thermal changes like temperature or flame emission.

Group two metals and alkaline earth metals dissociate into atoms when aspirated into a flame.

The solvent evaporates, leaving the salt to vaporize and dissociate into gaseous atoms in the flame.

Metal atoms absorb heat and get excited to higher energy levels, then emit light radiation as they fall back to their ground state.

The intensity of emitted light radiation is proportional to the concentration of the solution.

Different metals emit radiation at specific wavelengths, such as sodium at 589 nanometers and potassium at 766 nanometers.

Detector response (e) is given by the expression e = K * Alpha * C, where K is a constant, Alpha is the efficiency of atomic excitation, and C is the concentration.

The sample is injected into the flame photometer through a nebulizer, which mixes with air to aspirate the sample.

LPG is passed to the mixing chamber where it mixes with the sample before the flame is lit.

The flame causes evaporation, vaporization, dissociation, excitation, and emission of different radiations based on the metal present.

The emitted radiation passes through a lens and filter, which isolates the specific wavelength to be measured.

A photodetector converts the emitted radiation into an electrical signal, which is then amplified and displayed.

The burner is the source of flame in the flame photometer, and the nebulizer ensures a homogeneous solution is sent into the flame at a balanced rate.

The optical system, consisting of a convex mirror and lens, focuses the emitted light into the slit of the filter.

The photodetector converts the emitted radiation into an electrical signal proportional to the light intensity.

Flame photometry is used for both qualitative and quantitative analysis of materials in biological fluids and plant material.

It is also used for determining sodium, potassium, and calcium ions in water samples and soil extracts.

Flame photometry is utilized for the determination of calcium ions in cement and glasses.