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

La spectroscopie d’émission de plasma utilise trois types d’instruments de base.
Les spectromètres d’émission plasma séquentiels mesurent une raie d’émission à la fois, tandis que les instruments multicanaux et à transformée de Fourier mesurent simultanément plusieurs raies d’émission.
Les spectromètres séquentiels utilisent généralement un monochromateur à réseau, où le réseau est tourné pour focaliser différentes longueurs d’onde sur la fente de sortie.
Par exemple, dans les spectromètres à balayage orienté, le monochromateur tourne rapidement à une longueur d’onde proche d’une raie d’émission, puis tourne par petits pas sur cette ligne.
En revanche, les spectromètres à échelle à balayage ont un tube photomultiplicateur mobile derrière une plaque d’ouverture, le réseau à échelle dispersant les longueurs d’onde dans un large réseau qui peut être détecté une fente à la fois.
Certains instruments multicanaux utilisent un polychromateur à réseau pour mesurer plusieurs raies d’émission simultanément avec des tubes photomultiplicateurs positionnés derrière des fentes de sortie fixes.
D’autres instruments multicanaux utilisent des spectrographes pour des mesures simultanées, en utilisant des dispositifs d’injection de charge bidimensionnels ou des dispositifs à couplage de charge comme transducteurs.
Bien que les spectromètres à transformée de Fourier offrent une large couverture de longueur d’onde, ils ne sont pas largement utilisés dans l’AES en raison de leurs diverses limitations.

spectroscopie d'émission atomique à plasma inductif : instrumentation

Inductively Coupled Plasma Atomic Emission Spectroscopy: Instrumentation

Le plasma inductif (ICP) est la source de plasma couramment utilisée dans la spectroscopie d'émission atomique (AES), une technique qui détecte et analyse divers éléments dans un échantillon. Cette méthode est souvent appelée spectroscopie d'émission atomique à plasma inductif (ICP-AES).

Il existe trois principaux types d'instruments de spectroscopie d'émission atomique à plasma inductif (ICP-AES) : les instruments séquentiels, multicanaux simultanés et à transformée de Fourier, ces derniers étant moins couramment utilisés. L'ICP-AES séquentiel analyse chaque élément individuellement, l'instrument étant programmé pour passer d'une ligne d'élément à une autre, en s'arrêtant quelques secondes à chaque fois pour mesurer les intensités des lignes de manière satisfaisante. D'autre part, les instruments multicanaux sont conçus pour mesurer les intensités des lignes d'émission de plusieurs éléments simultanément ou presque. Bien que les instruments séquentiels soient plus simples, ils nécessitent plus de temps et de consommation d'échantillons, ce qui les rend plus coûteux à long terme.

Les spectromètres d'émission séquentiels et multicanaux peuvent utiliser soit un spectromètre à réseau classique, soit un spectromètre à échelle. Les monochromateurs à réseau, souvent présents dans les instruments séquentiels, utilisent un réseau holographique avec 2400 ou 3600 rainures par millimètre. Le réseau est mis en rotation avec un moteur pas à pas à commande numérique pour focaliser différentes longueurs d'onde de manière séquentielle et précise sur la fente de sortie. Les spectromètres à balayage progressif sont des instruments séquentiels qui balayent très rapidement une longueur d'onde proche d'une ligne d'intérêt avant de ralentir pour balayer la ligne par petits pas. Cette méthode minimise le temps passé dans les régions de longueur d'onde non utiles.

D'autre part, un spectromètre à échelle peut fonctionner soit comme un instrument de balayage, soit comme un spectromètre multicanal simultané. Les instruments multicanaux simultanés intègrent soit un polychromateur, soit un spectrographe. Les polychromateurs contiennent une série de tubes photomultiplicateurs pour la détection, mais les spectrographes utilisent des dispositifs d'injection de charge bidimensionnels (CID) ou des dispositifs à couplage de charge (CCD) comme transducteurs. Dans certains spectromètres d'émission multicanaux, les photomultiplicateurs sont situés derrière des fentes fixes le long de la courbe focale d'un polychromateur à réseau.

Bien qu'ils ne soient pas largement utilisés dans l'AES, les spectromètres à transformée de Fourier offrent des avantages tels qu'une large couverture de longueur d'onde, une vitesse, une haute résolution, des mesures de longueur d'onde très précises, une large plage dynamique, une taille compacte et un débit optique important. Dans l'ensemble, les instruments AES offrent différentes capacités, du balayage séquentiel à la détection multicanal simultanée et à l'analyse par transformée de Fourier, permettant aux chercheurs et aux analystes de choisir l'approche la plus adaptée à leurs besoins analytiques spécifiques.

Spectroscopie d'émission atomique à plasma inductif : instrumentation

Le plasma à couplage inductif (ICP) est la source de plasma couramment utilisée dans la spectroscopie d’émission atomique (AES), une technique qui détecte et analyse ...

inductively-coupled-plasma-atomic-emission-spectroscopy

Education

Enseignement

JoVE Core

Analytical Chemistry

Chimie analytique

Unit 1

Unité 1

Atomic Spectroscopy

Spectroscopie atomique

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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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