Name: atomic absorption spectroscopy for trace metals
Uploaded: 2024-12-05T18:32:14.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Physical Science

Waves and Electromagnetic Radiation

3.2.9-12.X

Atomic Absorption Spectroscopy: Overview

A espectroscopia de absorção atômica, ou AAS, é uma técnica de análise elementar baseada no princípio da absorção de radiação eletromagnética resultando em excitação eletrônica.
No AAS, a amostra é primeiro atomizada - convertendo analitos em átomos em fase gasosa. Embora a temperatura da chama excite alguns átomos em fase gasosa, a maioria permanece sem excitação.
Quando a radiação eletromagnética de um determinado comprimento de onda irradia um átomo, ela é absorvida se fornecer a energia exata para uma transição eletrônica para um orbital de energia mais alta.
A diferença nas intensidades de radiação incidente e transmitida mede a radiação absorvida, quantificando o analito.
O AAS segue a lei de Beer-Lambert, onde a absorbância depende diretamente da concentração dos átomos da fase gasosa na chama, assumindo um comprimento de caminho constante na chama.
Notavelmente, o AAS oferece alta sensibilidade com limites de detecção em níveis de nanogramas por mililitro e é amplamente utilizado para análise de traços de metais.
No entanto, o AAS requer sólidos em fase líquida ou voláteis. Além disso, requer um espectrômetro de fonte contínua de alta resolução ou fontes de radiação características para cada elemento a ser analisado.

espectroscopia de absorção atômica: visão geral

A espectroscopia de absorção atômica (AAS) é uma técnica usada para analisar elementos medindo a radiação eletromagnética (EMR) absorvida pelos átomos, o que faz com que eles transitem para uma órbita de energia mais alta. A etapa mais crucial na AAS é a atomização, onde o analito é convertido em átomos na fase gasosa, normalmente por meio de uma chama ou forno. Alguns desses átomos tornam-se termicamente excitados na chama, enquanto a maioria permanece no estado fundamental.

Quando irradiados por EMR de um comprimento de onda específico, esses átomos em fase gasosa no estado fundamental absorvem a radiação somente se ela fornecer a energia necessária para sua excitação eletrônica. A diferença entre a potência radiante incidente e transmitida da EMR é a medida da radiação absorvida, que quantifica o analito.

As linhas de absorção atômica são altamente estreitas, pois são geradas a partir de transições eletrônicas características desacompanhadas de transições rotacionais e vibracionais. A AAS segue a lei de Beer-Lambert, que afirma que a quantidade de luz absorvida é diretamente proporcional à concentração dos átomos absorventes, assumindo um comprimento de caminho constante. A AAS é uma técnica seletiva e sensível com limites de detecção na faixa de nanogramas por mililitro. É amplamente utilizada para análise de metais traço nos campos clínico, farmacêutico, alimentício, de mineração, ambiental e agrícola.

As limitações da AAS incluem a necessidade de amostras sólidas voláteis ou em fase de solução para análise. Além disso, as fontes de radiação para AAS devem ser fontes contínuas de alta resolução ou fontes de linha separadas para cada análise elementar.

Espectroscopia de Absorção Atômica: Visão Geral

A espectroscopia de absorção atômica (AAS) é uma técnica utilizada para analisar elementos por meio da medição da radiação eletromagnética (EMR) absorvida pelos átomos, o que causa ...

Education

JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidade 1

Atomic Spectroscopy

Espectroscopia Atômica

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

atomic absorption spectroscopy for trace metals

Atomic absorption spectroscopy (AAS) measures trace metals by tracking how atoms absorb electromagnetic radiation (EMR). The absorbed light makes atoms move to a higher-energy orbit. In AAS, the key step is atomization, which converts the sample into gas-phase atoms. A flame or a furnace is typically used for this step.

Inside the flame, some atoms become thermally excited. Most stay in the ground state, which is the lowest-energy state. These ground-state gas-phase atoms absorb EMR only when the wavelength supplies the right energy for electronic excitation. The change between incident and transmitted radiant power shows how much radiation was absorbed, and that value is used to quantify the analyte.

AAS produces very narrow atomic absorption lines. This happens because the signal comes from characteristic electronic transitions without rotational or vibrational transitions. The method also follows the Beer-Lambert law, which states that absorbed light is directly proportional to the concentration of the absorbing atoms when the path length stays constant.

AAS is selective and sensitive, with detection limits in the nanogram per milliliter range. It is widely used for trace metal analysis in clinical, pharmaceutical, food, mining, environmental, and agricultural work. The method does have limits. It usually needs solution-phase samples or volatile solid samples. It also requires radiation sources that are either high-resolution continuum sources or separate line sources for each elemental analysis.

Atomic Absorption Spectroscopy for Trace Metals

atomic-absorption-spectroscopy-trace-metals

atomic spectroscopy: absorption, emission, and fluorescence

atomic-spectroscopy-absorption-emission-and-fluorescence

Element Analysis with Atomic Light Spectra

Atomic spectroscopy is used to identify and measure elements by their light signals. It supports both qualitative analysis, which tells what is present, and quantitative analysis, which tells how much is present. The optical methods in this group are atomic absorption spectroscopy, atomic emission spectroscopy, and atomic fluorescence spectroscopy. These methods begin with atomization. In this step, a solid, liquid, or solution sample is changed into gas-phase atoms and ions. Once the sample...

atomic spectroscopy: effects of temperature

atomic-spectroscopy-effects-of-temperature

How Heat Changes Atomic Spectra

Heat changes atomic spectra by affecting atomization, excitation, ionization, and line shape. In atomic spectroscopy, atomization means converting a sample into gas-phase atoms and ions. The flame temperature needed for this step changes how efficiently the method works and shifts the balance between excited and ground-state atoms. At thermal equilibrium, the relative numbers of excited and ground-state atoms can be estimated with the Maxwell-Boltzmann distribution. A small temperature rise...

atomic absorption spectroscopy: overview

Atomic absorption spectroscopy (AAS) measures trace metals by tracking how atoms absorb electromagnetic radiation (EMR). The absorbed light makes atoms move to a higher-energy orbit. In AAS, the key step is atomization, which converts the sample into gas-phase atoms. A flame or a furnace is typically used for this step. Inside the flame, some atoms become thermally excited. Most stay in the ground state, which is the lowest-energy state. These ground-state gas-phase atoms absorb EMR only when...

atomic absorption spectroscopy: instrumentation

atomic-absorption-spectroscopy-instrumentation

Atomic Absorption Spectroscopy: Key Parts

Atomic absorption spectrophotometry uses a set of key parts to measure light absorbed by atoms. The main components are a radiation source, an atomizer, a monochromator, and a detector. Each part has a specific job in the instrument. The radiation source is usually a hollow-cathode lamp, or HCL, or an electrodeless-discharge lamp, or EDL. Both produce a narrow emission line at the needed wavelength. Some instruments instead use continuum sources with high-resolution monochromators to narrow...

atomic absorption spectroscopy: radiation and light sources

atomic-absorption-spectroscopy-radiation-and-light-sources

Choosing Light Sources for AAS Measurements

Atomic absorption spectroscopy (AAS) uses a light source that emits a very narrow range of wavelengths. This is needed because the source must match the absorption behavior of the analyte atom. The choice of source also depends on giving a precise, intense emission at the right wavelength for accurate detection. Two common line sources in AAS are hollow-cathode lamps (HCLs) and electrodeless-discharge lamps (EDLs). These lamps are selected based on the element being analyzed and the level of...

atomic absorption spectroscopy: atomization methods

atomic-absorption-spectroscopy-atomization-methods

Atomic Absorption Spectroscopy: Sample Atomization

Atomic absorption spectroscopy uses sample atomization to turn a liquid specimen into free atoms for analysis. The two main approaches are flame atomization and electrothermal atomization. Both methods prepare the sample so its atoms can be measured by the instrument. Flame atomization uses a nebulizer and spray chamber to mix the sample with a fuel-oxidant mixture. This creates a fine aerosol mist that enters the burner. The fuel and oxidant are usually close to a stoichiometric ratio, but a...

atomic absorption spectroscopy: interference

atomic-absorption-spectroscopy-interference

Correcting Errors in Atomic Absorption Spectroscopy

Atomic absorption spectroscopy interference can create systematic error by making the analytical signal or the background look stronger or weaker than it should be. In atomic absorption measurements, these errors are usually grouped as spectral interference, chemical interference, and physical interference. Spectral interference happens when signals from other elements or molecules overlap with the analyte signal, the substance being measured. This overlap can falsely raise or hide the analyte...

atomic absorption spectroscopy: lab

AAS Sample Prep and Calibration

Atomic absorption spectroscopy (AAS) depends on careful sample preparation and calibration. Samples must be turned into clear solutions before measurement. That often means extra treatment to dissolve materials such as soils, animal tissues, and minerals. Common sample prep methods include hot mineral acids, wet ashing, combustion in closed containers, high-temperature ashing, and fusion with reagents. These steps help make the sample suitable for AAS analysis. Solutions that contain organic...

atomic emission spectroscopy: overview

Atomic Emission Spectroscopy for Element Analysis

Atomic emission spectroscopy is used to identify the elements in a sample by measuring the light they emit. Atoms are first excited to higher energy levels by thermal energy from hot sources such as plasma, arcs, or sparks. When they fall back to lower energy levels, they give off light at specific wavelengths. Each element produces its own set of lines, so the emission spectrum can show both what is present and how much is there. AES instruments are similar to atomic absorption spectrometers,...

atomic emission spectroscopy: instrumentation

atomic-emission-spectroscopy-instrumentation

AES Sample Handling and Detection

Atomic emission spectrometry (AES) uses sample handling, atomization, and detection parts to measure emitted light from atoms and ions. The sample must first be changed into a gas-phase form so it can produce a measurable signal. AES uses two main atomizer types. Continuous atomizers, such as flames and plasmas, feed the sample in a steady stream. Discrete atomizers add one sample at a time with syringes or autosamplers. The electrothermal atomizer is the most common discrete type. Many...

atomic emission spectroscopy: interference

atomic-emission-spectroscopy-interference

Reducing Interference in AES Signals

Atomic emission spectroscopy (AES) can produce interfering signals when atoms and molecules in a flame or plasma emit overlapping light. High-temperature atomizers excite many species at once, including oxides, hydroxides, and flame combustion products. These extra emissions can make the analyte signal harder to read. Spectral interference happens when emission lines or bands overlap. One way to reduce it is to improve instrument resolution. Another is to choose a different emission line for...

inductively coupled plasma atomic emission spectroscopy: principle

inductively-coupled-plasma-atomic-emission-spectroscopy-principle

ICP-AES Torch and Sample Analysis

Inductively coupled plasma atomic emission spectroscopy uses a plasma torch to analyze elements in a sample. This method is also called inductively coupled plasma optical emission spectroscopy, or ICP-OES. It is widely used because the plasma creates a strong environment for elemental analysis. The ICP source, or torch, contains three concentric quartz tubes. Argon gas flows through the tubes. A spark from a Tesla coil starts the ionization of argon and creates a high-temperature plasma. The...

inductively coupled plasma atomic emission spectroscopy: instrumentation

inductively-coupled-plasma-atomic-emission-spectroscopy

ICP-AES Instrument Types and Detection

Inductively coupled plasma atomic emission spectroscopy, or ICP-AES, uses an inductively coupled plasma to detect and analyze elements in a sample. The method measures the light given off by atoms, which helps identify and compare different elements. It is a common approach in atomic emission spectroscopy. ICP-AES instruments are built in three main forms: sequential, simultaneous multichannel, and Fourier transform instruments. Fourier transform designs are less commonly used, but they are...

atomic emission spectroscopy: lab

Plasma Sources in Atomic Emission Spectroscopy

Atomic emission spectroscopy uses plasma sources to identify elements by their light. The method creates abundant spectra with characteristic emission lines. Inductively coupled plasma, or ICP, is especially useful because it gives strong quantitative data. It works well under stable conditions, with low noise, low background, and few interferences. Newer air-operated microwave sources are also being studied. These sources may be more cost-effective than conventional ICP systems. Atomic...

atomic fluorescence spectroscopy

Measuring Elements by Atomic Fluorescence

Atomic fluorescence spectroscopy measures elements by detecting the light atoms give off after they are excited by electromagnetic radiation. The atoms are first placed in a flame, furnace, or plasma. They absorb energy, become excited, and then release that energy as they return to their original state. The emitted light is called fluorescence. The fluorescence is observed at a right angle to the incoming beam. This setup helps separate the emitted light from the light used to excite the...

flame photometry: overview

Flame Emission Spectrometry Basics

Flame emission spectrometry uses a flame to excite elements in a sample so their light can be measured. It is also called flame photometry. The method can be used for both qualitative and quantitative analysis of elements. The idea became established in the early 1860s when Kirchhoff and Bunsen showed that specific elements give off characteristic radiation in a flame. The first instrument for this purpose measured sodium in plant ash with a Bunsen flame. A major problem was how to add the...

flame photometry: lab

Flame Photometry and Metal Detection

Flame photometry is a method for detecting metals by measuring the light they emit in a flame. A solution such as potassium chloride is aspirated into the flame. The solvent evaporates first. The remaining salt becomes dehydrated and then dissociates into free gaseous atoms in the ground state. Some of these atoms absorb energy from the flame and move to an excited state. When they return to the ground state, they emit photons at characteristic wavelengths. These emissions are very narrow...

key terms and concepts

Learn how atomic absorption spectroscopy measures trace metals by atomization, light absorption, and the Beer-Lambert law in real samples.

Atomic Absorption Spectroscopy for Trace Metals | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Travelling Waves

A wave is a disturbance that propagates from its source, repeating itself periodically, and is typically associated with simple harmonic motion. ...

Wave Parameters

The simplest mechanical waves are associated with simple harmonic motion and repeat themselves for several cycles. These simple harmonic waves can be ...

Equations of Wave Motion

Mathematically, the motion of a wave can be studied using a wavefunction. Consider a string oscillating up and down in simple harmonic motion, having a ...

Graphing the Wave Function

Consider the wave equation for a sinusoidal wave moving in the positive x-direction. The wave equation is a function of both position and time. From the ...

/files/media/science-education/science-education-thumbs/14721.jpg

Velocity and Acceleration of a Wave

A wave propagates through a medium with a constant speed, known as a wave velocity. It is different from the speed of the particles of the medium, which ...

Speed of a Transverse Wave

The speed of a wave depends on the characteristics of the medium. For example, in the case of a guitar, the strings vibrate to produce the sound. The ...

/files/media/science-education/science-education-thumbs/14722.jpg

problem-solving-tuning-of-a-guitar-string

Problem-Solving: Tuning of a Guitar String

In the case of stringed instruments like the guitar, the elastic property that determines the speed of the sound produced is its linear mass density or ...

/files/media/science-education/science-education-thumbs/14744.jpg

Kinetic and Potential Energy of a Wave

All forms of waves carry energy; this is directly visualized in nature. For instance, the waves of earthquakes are so intense that they can shake huge ...

Energy and Power of a Wave

The total energy associated with a wavelength is the sum of the potential energy and the kinetic energy. The average rate of energy transfer associated ...

Students who demonstrate understanding can use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media. Clarifying Statement: Examples of data could include electromagnetic radiation traveling in a vacuum and glass, sound waves traveling through air and water, and seismic waves traveling through the Earth. Assessment Boundry: Assessment is limited to algebraic relationships and describing those relationships qualitatively.

3.2.9-12.T

Interference and Superposition of Waves

When two waves of the same nature occur in the same region simultaneously, they result in interference. Interference of waves implies that the net effect ...

Sound Waves: Interference

Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure ...

Interference: Path Lengths

Consider two sources of sound, that may or may not be in phase, emitting waves at a single frequency, and consider the frequencies to be the same.
Two ...

/files/media/science-education/science-education-thumbs/14727.jpg

Sound Waves: Resonance

Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical ...

Electromagnetic Waves

James Clerk Maxwell formulated a single theory combining all the electric and magnetic effects scientists knew during that time, calling the phenomena his ...

The Electromagnetic Spectrum

Electromagnetic waves are categorized according to their wavelengths and frequencies, giving the electromagnetic spectrum. These waves are classified as ...

Electromagnetic Wave Equation

Maxwell&#39;s equations for electromagnetic fields are related to source charges, either static or moving. These fields act on a test charge, whose ...

propagation-speed-of-electromagnetic-waves

Propagation Speed of Electromagnetic Waves

Electromagnetic waves are consistent with Ampere&#39;s law. Assuming there is no conduction current Ampere&#39;s law is given as:


Consider a plane ...

Electromagnetic Waves in Matter

Electromagnetic waves can travel in the vacuum as well as in matter. For example light, which is an electromagnetic wave, can travel through air, water, ...

Energy Carried By Electromagnetic Waves

Anyone who has used a microwave oven knows there is energy in electromagnetic waves. Sometimes, this energy is obvious, such as in the summer sun&#39;s ...

Intensity Of Electromagnetic Waves

The energy transport per unit area per unit time, or the Poynting vector, gives the energy flux of an electromagnetic wave at any specific time. For a ...

Momentum And Radiation Pressure

An object absorbing an electromagnetic wave would experience a force in the direction of propagation of the wave. This force occurs because ...

Radiation Pressure: Problem Solving

The radiation pressure applied by an electromagnetic wave on a perfectly absorbing surface equals the energy density of the wave. The wave&#39;s momentum ...

Students who demonstrate understanding can evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model and that for some situations one model is more useful than the other.  Clarifying Statement: Emphasis is on how the experimental evidence supports the claim and how a theory is generally modified in light of new evidence.  Examples of a phenomenon could include resonance, interference, diffraction, and photoelectric effect.  Assessment Boundry: Assessment does not include using quantum theory.

3.2.9-12.V

Absorption of Radiation

The rate of heat transfer by emitted radiation is described by the Stefan-Boltzmann law of radiation:

where &#963; is the Stefan-Boltzmann constant, a ...

Students who demonstrate understanding can evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.  Clarifying Statement: Emphasis is on the idea that photons associated with different frequencies of light have different energies, and the damage to living tissue from electromagnetic radiation depends on the energy of the radiation.  Examples of published materials could include trade books, magazines, web resources, videos, and other passages that may reflect bias.  Assessment Boundry: Assessment is limited to qualitative descriptions.

3.2.9-12.W

Energy Transfer in Chemical Reactions

Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ...

Dye-sensitized Solar Cells

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University
Today&#39;s modern world requires the use of a large amount of energy. While ...

The Wave Nature of Light

The nature of light has been a subject of inquiry since antiquity. In the seventeenth century, Isaac Newton performed experiments with lenses and prisms ...

The electromagnetic spectrum consists of all the types of electromagnetic radiation arranged according to their frequency and wavelength. Each of the ...

Photoelectric Effect

When light of a particular wavelength strikes a metal surface, electrons are emitted. This is called the photoelectric effect. The minimum frequency of ...

dual-nature-of-electromagnetic-em-radiation

Dual Nature of Electromagnetic (EM) Radiation

Electromagnetic (EM) radiation consists of electric and magnetic field components oscillating in planes perpendicular to each other and mutually ...

interaction-of-em-radiation-with-matter-spectroscopy

Interaction of EM Radiation with Matter: Spectroscopy

Electromagnetic (EM) radiation can be considered an oscillating electric and magnetic field propagating through a medium that can interact with matter in ...

molecular-spectroscopy-absorption-and-emission

Molecular Spectroscopy: Absorption and Emission

Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational ...

Spectrophotometry: Introduction

Spectrophotometry is the quantitative measurement of the absorption, reflection, diffraction, or transmission of electromagnetic radiation through a ...

ultraviolet-and-visible-uvvis-spectroscopy-overview

Ultraviolet and Visible (UV&ndash;Vis) Spectroscopy: Overview

Ultraviolet&#8211;visible (UV&#8211;visible or UV&#8211;Vis) spectroscopy is an analytical technique that investigates the interaction between matter and ...

Infrared (IR) Spectroscopy: Overview

When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation ...

Raman Spectroscopy: Overview

The underlying principle of Raman spectroscopy is based on the interaction between light and matter, specifically molecules&#39; inelastic scattering of ...

Atomic absorption spectroscopy (AAS) is a technique used to analyze elements by measuring electromagnetic radiation (EMR) absorbed by atoms, which causes ...

Nuclear Magnetic Resonance (NMR): Overview

Nuclear magnetic resonance (NMR) is a phenomenon exhibited by certain nuclei that can absorb characteristic radio frequency radiation under certain ...

Students who demonstrate understanding can communicate technical information about how some technological devices use the principles of wave behavior and wave interactions with matter to transmit and capture information and energy.  Clarifying Statement: Examples could include solar cells capturing light and converting it to electricity; medical imaging; and communications technology.  Assessment Boundry: Assessments are limited to qualitative information.  Assessments do not include band theory.

Atomic Absorption Spectroscopy for Trace Metals

Description

Transcript

Tags

More videos by Standards