Name: icp-aes instrument types and detection
Uploaded: 2024-12-05T18:32:15.000Z
Duration: 1 min 26 s
Channel: JoVE

A espectroscopia de emissão de plasma usa três tipos básicos de instrumentos.
Os espectrômetros sequenciais de emissão de plasma medem uma linha de emissão por vez, enquanto os instrumentos multicanal e de transformada de Fourier medem simultaneamente várias linhas de emissão.
Os espectrômetros sequenciais normalmente usam um monocromador de grade, onde a grade é girada para focar diferentes comprimentos de onda na fenda de saída.
Por exemplo, em espectrômetros de varredura de giro, o monocromador gira rapidamente para um comprimento de onda próximo a uma linha de emissão e, em seguida, gira em pequenos passos através dessa linha.
Em contraste, os espectrômetros echelle de varredura têm um tubo fotomultiplicador móvel atrás de uma placa de abertura, com a grade echelle espalhando os comprimentos de onda em uma ampla matriz que pode ser detectada uma fenda de cada vez.
Alguns instrumentos multicanais usam um policromador de grade para medir várias linhas de emissão simultaneamente com tubos fotomultiplicadores posicionados atrás de fendas de saída fixas.
Outros instrumentos multicanais usam espectrógrafos para medições simultâneas, empregando dispositivos bidimensionais de injeção de carga ou dispositivos de carga acoplada como transdutores.
Embora os espectrômetros com transformada de Fourier ofereçam ampla cobertura de comprimento de onda, eles não são amplamente utilizados no AES devido às suas várias limitações.

espectroscopia de emissão atômica com plasma indutivamente acoplado: instrumentação

Inductively Coupled Plasma Atomic Emission Spectroscopy: Instrumentation

O plasma indutivamente acoplado (ICP) é a fonte de plasma comumente utilizada na espectroscopia de emissão atômica (AES), uma técnica que detecta e analisa vários elementos em uma amostra. Este método é frequentemente chamado de espectroscopia de emissão atômica com plasma indutivamente acoplado (ICP-AES).

Existem três tipos principais de instrumentos de espectroscopia de emissão atômica com plasma indutivamente acoplado (ICP-AES): instrumentos sequenciais, multicanais simultâneos e de transformada de Fourier, sendo este último menos comumente usado. A ICP-AES sequencial analisa cada elemento individualmente, onde o instrumento é programado para se mover de uma linha de elemento para outra, parando alguns segundos em cada uma para medir as intensidades das linhas de forma satisfatória. Por outro lado, os instrumentos multicanais são projetados para medir as intensidades das linhas de emissão para vários elementos simultaneamente ou quase isso. Embora os instrumentos sequenciais sejam mais simples, eles exigem mais tempo e consumo de amostras, tornando-os mais caros a longo prazo.

Espectrômetros de emissão sequenciais e multicanais podem utilizar um espectrômetro de grade clássico ou um espectrômetro echelle. Monocromadores de grade, frequentemente apresentados em instrumentos sequenciais, usam uma grade holográfica com 2400 ou 3600 ranhuras por milímetro. A grade é girada com um motor de passo controlado digitalmente para focar diferentes comprimentos de onda sequencialmente e precisamente na fenda de saída. Espectrômetros de varredura rápida são instrumentos sequenciais que varrem muito rapidamente até um comprimento de onda próximo a uma linha de interesse antes de desacelerar para varrer através da linha em pequenos passos. Este método minimiza o tempo gasto em regiões de comprimento de onda não úteis.

Por outro lado, um espectrômetro echelle pode operar como um instrumento de varredura ou um espectrômetro multicanal simultâneo. Instrumentos multicanais simultâneos incorporam um policromador ou um espectrógrafo. Os policromadores contêm uma série de tubos fotomultiplicadores para detecção, mas os espectrógrafos usam dispositivos de injeção de carga bidimensionais (CIDs) ou dispositivos de carga acoplada (CCDs) como transdutores. Em alguns espectrômetros de emissão multicanal, os fotomultiplicadores estão localizados atrás de fendas fixas ao longo da curva focal de um policromador de grade.

Embora não sejam amplamente utilizados em AES, os espectrômetros de transformada de Fourier oferecem benefícios como ampla cobertura de comprimento de onda, velocidade, alta resolução, medições de comprimento de onda altamente precisas, grande faixa dinâmica, tamanho compacto e grande rendimento óptico. No geral, os instrumentos de AES fornecem diferentes capacidades, desde varredura sequencial até detecção multicanal simultânea e análise de transformada de Fourier, permitindo que pesquisadores e analistas escolham a abordagem mais adequada para suas necessidades analíticas específicas.

Espectroscopia de Emissão Atômica com Plasma Indutivamente Acoplado: Instrumentação

O plasma indutivamente acoplado (ICP) é a fonte de plasma comum usada em espectroscopia de emissão atômica (AES), uma técnica que detecta e analisa v...

inductively-coupled-plasma-atomic-emission-spectroscopy

Education

JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidade 1

Atomic Spectroscopy

Espectroscopia Atômica

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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 part of the instrument family. Each type handles wavelengths and element signals in a different way.

Sequential ICP-AES measures elements one at a time. The instrument moves from one element line to another and pauses for a few seconds at each point so it can measure line intensity well. These instruments are simpler, but they take more time and use more sample, so they can cost more over time.

Multichannel instruments measure emission lines for several elements at the same time, or nearly at the same time. Sequential and multichannel emission spectrometers can use either a classical grating spectrometer or an echelle spectrometer. In many sequential instruments, a grating monochromator uses a holographic grating with 2400 or 3600 grooves per millimeter, and a digitally controlled stepper motor rotates the grating to send different wavelengths to the exit slit.

Some sequential systems are slew-scan spectrometers. They move quickly to a wavelength near the line of interest and then slow down to scan across the line in small steps. This reduces time spent in wavelength regions that do not help the measurement.

An echelle spectrometer can work as a scanning instrument or as a simultaneous multichannel spectrometer. Simultaneous multichannel instruments may use a polychromator or a spectrograph. Polychromators use a series of photomultiplier tubes, while spectrographs use two-dimensional charge-injection devices, or CIDs, and charge-coupled devices, or CCDs, as transducers.

In some multichannel emission spectrometers, photomultipliers sit behind fixed slits along the focal curve of a grating polychromator. Fourier transform spectrometers are not widely used in AES, but they offer wide wavelength coverage, speed, high resolution, accurate wavelength measurements, a large dynamic range, compact size, and high optical throughput. These instrument choices let analysts match the system to the needs of a specific sample and measurement.

ICP-AES Instrument Types and Detection

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 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, 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 ICP-AES instruments work, including sequential, multichannel, and Fourier transform designs, plus the detectors and spectrometers used to measure elements.

ICP-AES Instrument Types and Detection | JoVE K12

analytical chemistry

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ICP-AES Instrument Types and Detection

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