Name: flame emission spectrometry basics
Uploaded: 2024-12-05T18:32:16.000Z
Duration: 1 min 2 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Earth and Space Science

Space Systems

3.3.9-12.C

Flame Photometry: Overview

火焰光度法，或称火焰发射光谱法，利用火焰激发样品溶液。
火焰应具有足够的能量以实现原子化，且在相关波长处具有较低的发射和吸收，并能够在低气体流速下运行。
通常使用丙烷-空气火焰，因为丁烷-空气和天然气-空气火焰由于温度较低而灵敏度较差。
火焰光度计采用雾化器-燃烧器系统将样品溶液转化为雾状或气溶胶。燃烧器主要有两种类型。
预混式或层流燃烧器在汽化室中产生细微的雾化液滴，随后与燃料气体和氧化剂气体混合，再到达燃烧器头部。
全消耗型或湍流燃烧器由三个同心管组成，分别输送样品溶液、燃气和助燃气，使它们仅在燃烧器顶端混合。

火焰光度法：概述

火焰光度法（又称火焰发射光谱法），是一种使用火焰作为激发光源对样品中的元素进行定性分析和定量分析的技术。火焰光度法的概念是在 19 世纪 60 年代初由基尔霍夫（Kirchhoff）和本生（Bunsen）提出的，他们发现特定元素在火焰中被激发时会发出特征辐射。根据这一概念所开发出的第一台仪器能够使用本生焰来测量草木灰中的钠（Na）。然而，其中的挑战是：需要找到能够将样品引入到火焰中最有效的方法。直到 1929 年，当伦德加特（Lundegardh）推出雾化器时，才取得了重大突破，从而使其能够将样品重复地引入到火焰中。


 在火焰发射光谱法中，通过将高压气流穿过装有样品的毛细管末端并将其吸入雾室，雾化器便能够将液体样品转化为细雾或气溶胶。产生的气溶胶随后会被输送到燃烧器中，火焰的热量将会使得气溶胶发生脱溶，从而形成干燥颗粒，经过挥发后的颗粒能够产生自由原子以供分析。


 早期的仪器通常会使用石英棱镜摄谱仪和照相记录的方式来原子发射谱线进行分散和捕获。然而，滤光片和光电探测器的进步不仅取代了这些组件，同时还提高了准确度和便利性。


 火焰光度法指的是将样品溶液引入到雾化器，通过雾化器将其转化为细雾或气溶胶到过程。雾化后的样品将会与空气或氧气、丙烷或乙炔等燃料气体一起进入火焰。火焰提供了必要的热激发，这使得样品中的原子能够获得能量。当这些被激发的原子发生弛豫时，它们所发射的辐射就会被光电管或光电倍增管检测到。


 火焰光度法在测量钠、钾、锂和钙元素方面尤为有效。火焰光度法中使用的火焰通常是温度范围为 1900-2000 °C的丙烷-空气火焰，但也可以使用丁烷-空气或天然气-空气来对火焰进行替代。另外，火焰光度法同样也存在一些局限性，这可以通过使用更高的温度、更多的还原焰（例如空气-乙炔）和更高分辨率的光谱检测来进行克服。然而，与适用范围更广的火焰原子吸收光谱法或原子吸收光谱（AAS）技术相比，这些方法在成本上并不具有竞争力。

火焰光度法，又称火焰发射光谱法，是一种用于定性与定量分析样品中所含元素的技术。

Education

教育

JoVE Core

Analytical Chemistry

分析化学

Unit 1

第一单元

Atomic Spectroscopy

原子光谱

KEY TERMS AND CONCEPTS

关键术语与概念

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 sample to the flame in a steady way.

That problem changed in 1929, when Lundegardh introduced a nebulizer. A nebulizer turns a liquid sample into a fine mist, or aerosol. A high-pressure gas stream passes over a capillary tube, draws the sample into a spray chamber, and sends the aerosol to the burner.

At the burner, flame heat removes the solvent and leaves dry particles. These particles volatilize and form free atoms for analysis. Early instruments used quartz prism spectrographs and photographic recording to separate and capture the atomic emission lines. Later, optical filters and electrical photodetectors replaced those parts and made the method more precise and easier to use.

In a flame photometry setup, the sample solution enters the nebulizer and then the flame with air or oxygen and a fuel gas such as propane or acetylene. The flame supplies the thermal energy needed to excite the atoms. When the atoms return to a lower energy state, they emit radiation that is measured by a photocell or photomultiplier.

This method is especially useful for sodium, potassium, lithium, and calcium. A propane-air flame is commonly used and reaches about 1900 to 2000 degrees Celsius. Butane-air and natural gas-air flames can also be used. Some limits can be reduced with higher temperatures and more reducing flames, such as air-acetylene, together with higher-resolution spectrometric detection. Even so, these options are not as cost-competitive as flame atomic absorption spectrometry, also called AAS.

Flame Emission Spectrometry Basics

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

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 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 flame emission spectrometry uses a nebulizer, flame excitation, and photodetectors to measure elements like sodium, potassium, lithium, and calcium.

Flame Emission Spectrometry Basics | 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.

Arizona Science Standards

High School

Physical Science

HS+C.P1

HS+C.P1U1.2

the-principle-of-superposition-and-the-gravitational-field

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3.3.9-12.A

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3.3.9-12.D

Flame Emission Spectrometry Basics

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