Name: atomic emission spectroscopy for element analysis
Uploaded: 2024-12-05T18:32:15.000Z
Duration: 1 min 20 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Earth and Space Science

Space Systems

3.3.9-12.C

Atomic Emission Spectroscopy: Overview

A espectroscopia de emissão atômica, ou AES, permite a análise multielementar em uma amostra, onde todos os analitos podem ser excitados simultaneamente por descarga elétrica, chama ou plasma.
No AES, os átomos de estado excitado relaxam para fornecer emissões características, e a intensidade da emissão é diretamente proporcional à população de estado excitado.
Populações significativas de átomos de estado excitado são alcançadas empregando plasma de argônio de alta temperatura.
O plasma de argônio - uma mistura gasosa quente e eletricamente condutora de íons de argônio e elétrons - é gerado pela ionização de um fluxo de argônio. O plasma é sustentado indefinidamente por uma fonte de alimentação que mantém uma temperatura ideal para ionização adicional. 
Uma fonte de plasma baseada em radiofrequência chamada plasma indutivamente acoplado, ou ICP, pode atingir temperaturas de até 10.000 K. É uma fonte de excitação amplamente utilizada em AES, comumente referida como ICP-AES ou ICP-OES.
Outras fontes de plasma incluem plasma induzido por micro-ondas, plasma de corrente contínua, microplasmas e plasma induzido por laser.

espectroscopia de emissão atômica: visão geral

A espectroscopia de emissão atômica (AES) é uma técnica analítica utilizada para determinar a composição elementar de uma amostra analisando a luz emitida por átomos excitados. Na AES, os átomos em uma amostra são excitados para níveis de energia mais altos por energia térmica de fontes de alta temperatura, como plasma, arcos ou faíscas. Quando esses átomos excitados retornam a estados de energia mais baixos, eles emitem luz em comprimentos de onda específicos característicos de cada elemento. O espectro de emissão atômica resultante, que consiste em linhas discretas correspondentes a esses comprimentos de onda, permite identificar e quantificar vários elementos dentro da amostra.

A instrumentação de AES compartilha semelhanças com espectrômetros de absorção atômica, mas com adaptações específicas para a detecção de emissão. Fontes de alta temperatura, particularmente plasma indutivamente acoplado (ICP), são essenciais na AES, pois atingem energia suficiente para excitar os átomos para seus estados de emissão. Outras fontes de plasma incluem plasma induzido por micro-ondas (MIP) e plasma de corrente contínua (DCP). A fonte mais amplamente utilizada, ICP, atinge temperaturas de até 10.000 K, criando um ambiente estável para excitação e emissão consistentes. A ICP-AES, também conhecida como ICP-OES (espectrometria de emissão óptica), permite a análise multielementar posicionando vários detectores em uma matriz semicircular ao redor da fonte de emissão para capturar leituras simultâneas em uma faixa de comprimentos de onda.

A AES oferece várias vantagens em relação aos métodos tradicionais de absorção atômica, como técnicas de chama e eletrotérmicas. Devido às fontes de alta temperatura que dissociam moléculas complexas, a AES é menos suscetível a interferências químicas, permitindo leituras espectrais mais limpas. A técnica permite a análise multielementar simultânea, melhorando significativamente a eficiência analítica. Além disso, a AES cobre uma faixa de concentração mais ampla, tornando-a adequada para diversos tipos de amostra.

Apesar dessas vantagens, a AES tem suas limitações. Os espectros complexos produzidos por fontes de alta temperatura aumentam a probabilidade de interferências espectrais, complicando a análise quantitativa. Para lidar com esses desafios, os instrumentos de AES exigem sistemas ópticos de alta resolução, geralmente mais caros do que aqueles usados ​​em espectrometria de absorção atômica. Além disso, embora a AES seja poderosa para análise multielementar, as técnicas de absorção atômica continuam valiosas para a análise de elementos únicos devido à sua simplicidade, custo-benefício e precisão.

A AES é amplamente utilizada em monitoramento ambiental, ciência de materiais e laboratórios clínicos para analisar metais, elementos-traço e outras substâncias inorgânicas. Sua capacidade de realizar análises multielementares rápidas torna a AES particularmente útil para testar amostras de solo, água e biológicas. A alta sensibilidade e a ampla faixa elementar dos instrumentos de AES permitem medições precisas tanto em concentrações de traço quanto significativas, tornando-a uma ferramenta versátil para a análise elementar em vários campos científicos.

Na AES, a análise quantitativa depende da medição da intensidade da luz emitida, que é proporcional à população de átomos excitados. De acordo com a distribuição de Boltzmann, essa população de estado excitado depende da temperatura da fonte de excitação, com temperaturas mais altas produzindo maiores emissões. Curvas de calibração, frequentemente lineares em várias ordens de magnitude, são criadas pela análise de padrões conhecidos para correlacionar intensidades de emissão com concentrações elementares. Técnicas de padronização são cruciais para controlar variações na eficiência de excitação e outros fatores instrumentais, permitindo uma quantificação precisa de elementos em amostras diversas.

Espectroscopia de Emissão Atômica: Visão geral

A espectroscopia de emissão atômica (AES) é uma técnica analítica usada para determinar a composição elementar de uma amostra analisando a luz emitida por ...

Education

JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidade 1

Atomic Spectroscopy

Espectroscopia Atômica

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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, but they are built to detect emitted light. High-temperature sources are essential because they provide enough energy to excite atoms into their emission states. Inductively coupled plasma, or ICP, is the most widely used source. It can reach temperatures up to 10,000 K and creates a stable environment for steady excitation and emission. Other plasma sources used in AES include microwave-induced plasma, or MIP, and direct current plasma, or DCP.

ICP-AES is also called ICP-OES, which stands for optical emission spectrometry. This setup allows multielement analysis by placing multiple detectors in a semicircular array around the emission source. The detectors can record several wavelengths at the same time. That makes the method fast and useful when more than one element must be measured in the same sample.

AES has several advantages over traditional atomic absorption methods such as flame and electrothermal techniques. The high-temperature source helps break apart complex molecules, so chemical interferences are usually lower. The method also supports simultaneous multielement analysis, which improves efficiency. In addition, AES covers a wider concentration range, so it works with many different sample types.

The technique also has limits. High-temperature sources create complex spectra, which increases the chance of spectral interferences and can make quantitative analysis harder. AES instruments need high-resolution optical systems to separate the lines clearly, and these systems are often more expensive than those used in atomic absorption spectrometry. For single-element analysis, atomic absorption methods are still useful because they are simple, cost-effective, and precise.

AES is widely used in environmental monitoring, materials science, and clinical laboratories. It can analyze metals, trace elements, and other inorganic substances in soil, water, and biological samples. This makes it valuable for rapid testing across many scientific fields. The method is sensitive and can measure both trace and significant concentrations.

Quantitative AES depends on the intensity of the emitted light. That intensity is related to the number of atoms in the excited state. According to the Boltzmann distribution, this excited-state population depends on the temperature of the source, so higher temperatures produce more emission. To find concentration, scientists use calibration curves made from known standards, and they apply standardization methods to reduce the effects of changes in excitation efficiency and other instrument factors.

Atomic Emission Spectroscopy for Element Analysis

atomic-emission-spectroscopy-for-element-analysis

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 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...

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 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 emission spectroscopy uses emitted light to identify elements, compare ICP-AES and ICP-OES, and measure samples with calibration curves.

Atomic Emission Spectroscopy for Element Analysis | 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.

Louisiana Student Standards for Science

High School

Earth Science

Earth’s Place In The Universe

HS-ESS1-2

Chemistry

motion-and-stability-forces-and-interactions

Motion And Stability: Forces And Interactions

HS-PS2-6

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South Carolina College and Career Ready Science Standards

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Waves and Their Applications in Technologies for Information Transfer

C-PS4-4

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3.3.9-12.A

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Atomic Emission Spectroscopy: Instrumentation

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Atomic Absorption Spectroscopy: Radiation and Light Sources

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3.3.9-12.B

Spectrophotometry: Introduction

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3.3.9-12.D

Atomic Emission Spectroscopy for Element Analysis

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