Name: correcting errors in atomic absorption spectroscopy
Uploaded: 2024-12-05T18:32:14.000Z
Duration: 1 min 25 s
Channel: JoVE

AAS測定では、スペクトル、化学的、または物理的な干渉に遭遇し、検出された分析物信号の大きさを不明瞭にしたり、変化させたりすることがあります。
スペクトル干渉は、干渉物質または霧化炎からの信号が分析物の信号と重なり、分析物の吸光度が誤って上昇またはマスキングされる場合に発生します。
これは、Zeeman、Smith–Hieftje、または重水素バックグラウンド補正技術を使用して対処できます。さらに、高分解能分光器は、重なり合うスペクトル線によるスペクトル干渉を最小限に抑えることができます。 
化学的干渉の原因には、分析種とマトリックス成分との相互作用があり、不揮発性塩が生成され、霧化効率が低下します。
このような干渉は、高い霧化温度を使用するか、錯体化剤または離型剤を添加することで回避できます。
さらに、一部の原子分析物は分析中にイオン化し、吸収が低下する可能性があります。しかし、よりイオン化しやすい元素を添加することで、分析物のイオン化が抑制されます。
ガスの流量や火炎温度の変動など、化学的要因以外の要因から生じる物理的干渉は、頻繁なキャリブレーション、内部標準、またはサンプルへの既知の量の分析物の添加によって最小限に抑えられます。

原子吸光分光法: 干渉

Atomic Absorption Spectroscopy: Interference

干渉は、分析信号またはバックグラウンドを増強または減少させることにより、原子吸光 (AA) 測定における系統的誤差につながります。これらの干渉は、スペクトル干渉、化学干渉、および物理的干渉の 3 つの主なカテゴリに分類できます。

スペクトル干渉は、他の元素または分子からの信号が分析物信号と重なり、分析物の吸光度を誤って高めたり隠したりするときに発生します。この干渉は、ゼーマン、スミス-ヒーフチェ、または重水素バックグラウンド補正法を使用して補正できます。

ゼーマン補正法では、磁場を使用して吸収線を 3 つの偏光成分 (2 つの σ (シフト) と 1 つの π (シフトなし)) に分割します。分析物とバックグラウンドの吸光度は、磁場を交互に切り替えることで別々に測定され、複雑なマトリックスの精度が向上します。

スミス-ヒーフチェ補正法では、中空カソードランプ (HCL) を高電流でパルス駆動し、発光ラインを広げて自己反転させ、中央の分析ラインを減少させます。これにより、ラインの両側で強い発光が生じ、バックグラウンドに吸収されます。吸光度は通常および高電流条件下で測定され、分析物とバックグラウンド信号を区別できます。必要な光源は 1 つだけですが、特に自己反転が不十分な場合や回復が遅すぎる場合は、感度が低下します。

重水素 (D_2) バックグラウンド補正法では、D_2 ランプを広帯域光源として使用し、原子吸光分光法 (AAS) のバックグラウンド吸収を補正します。回転ミラーが狭帯域中空カソードランプ (HCL) と広帯域 D_2 ランプを交互に切り替えます。D_2 ランプは広い波長範囲にわたってバックグラウンド吸光度を測定し、HCL は特定の波長で分析物とバックグラウンドの吸光度を測定します。 2 つの信号の差から分析物の吸光度が分離されます。安価ではありますが、高精度の測定には適していません。

さらに、高解像度の分光計は、重なり合うスペクトル線によるスペクトル干渉を最小限に抑えることができます。分析前に分析物を溶媒で繰り返し抽出できる場合もあります。

化学干渉は、不要なマトリックス成分が分析物と相互作用して原子化効率が低下する場合に発生します。放出剤や錯化剤などの化学修飾剤をサンプルに追加して原子化を促進したり、干渉化合物の形成を防いだりすることができます。一般的な化学干渉には、イオン化や難溶性化合物の形成による干渉があります。

分析物と同じ温度でイオン化する元素または化合物は、分析物のイオン化を変化させる可能性があります。イオン化しやすい元素を含む溶液を過剰に追加することでイオン化を抑制でき、これにより分析物のイオン化が抑制されます。

さらに、分析物とサンプルマトリックス内の他の種との化学反応により、容易に原子化しない不揮発性化合物が形成されることがあります。これにより、吸収のための自由原子の形成が妨げられます。このような干渉は、化学競合物質の追加または非常に高い温度の使用によって回避されます。

実際のサンプルに類似したサンプルマトリックスを使用して校正標準を準備することができ、マトリックスから生じる化学干渉を補正するのに役立ちます。

ガス流量の変化や炎の温度変化などの非化学的要因から生じる物理的干渉は、噴霧または原子化プロセスに影響します。これらの干渉は、内部標準を使用するか、サンプルを希釈することで解決できます。サンプルマトリックスを変更し、同様のマトリックスを使用して校正標準を準備すると、物理的干渉をさらに減らすことができます。

干渉は、分析信号またはバックグラウンドを増強または減少させることにより、原子吸光(AA)測定の系統誤差につながります。これら。。。

atomic-absorption-spectroscopy-interference

Education

JoVE Core

Analytical Chemistry

分析化学

Unit 1

ユニット1

Atomic Spectroscopy

原子分光法

KEY TERMS AND CONCEPTS

主要用語と概念

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 absorbance. It can be reduced with Zeeman, Smith-Hieftje, or deuterium background correction methods. High-resolution spectrometers can also help minimize overlap from nearby spectral lines, and in some cases the analyte can be repeatedly extracted with a solvent before analysis.

The Zeeman correction method uses a magnetic field to split the absorption line into three polarized components. Two are shifted sigma components, and one is an unshifted pi component. The analyte and the background are measured separately by alternating the magnetic field, which improves accuracy in complex samples. The Smith-Hieftje method uses a hollow cathode lamp at high current. This broadens the emission line and causes self-reversal, where the central analytical line decreases. Strong emission remains on both sides of the line and is absorbed by the background. Absorbance is measured under normal and high-current conditions to separate analyte and background signals, but sensitivity can drop if self-reversal is weak or recovery is slow. The deuterium background correction method uses a D2 lamp as a broad-spectrum light source. A rotating mirror switches between the narrow-band hollow cathode lamp and the broad-band D2 lamp. The D2 lamp measures background absorbance over a wide wavelength range, while the hollow cathode lamp measures analyte and background absorbance at one wavelength. The difference between the two signals isolates the analyte absorbance, although this method is less precise in high-accuracy work.

Chemical interferences occur when matrix components in the sample react with the analyte and reduce atomization efficiency. A chemical modifier, such as a releasing agent or complexing agent, can be added to improve atomization or prevent interfering compounds from forming. Common chemical problems include ionization interference and refractory compound formation. If another element or compound ionizes at the same temperature as the analyte, it can change the analyte ionization. This can be suppressed by adding an excess of an element that ionizes more easily. Chemical reactions can also form nonvolatile compounds that do not atomize easily, which limits free atom formation for absorption. Adding a chemical competitor or using very high temperatures can help prevent this. Matching the calibration standards to the sample matrix also helps correct for matrix effects.

Physical interferences come from non-chemical changes, such as gas flow rate changes or flame temperature changes. These factors can affect nebulization or atomization. They can be reduced with internal standards, sample dilution, and matrix matching. Preparing calibration standards with a similar matrix can also help reduce physical interference and improve measurement reliability.

Correcting Errors in Atomic Absorption Spectroscopy

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atomic spectroscopy: absorption, emission, and fluorescence

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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...

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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...

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atomic absorption spectroscopy: instrumentation

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Atomic Absorption Spectroscopy: Key Parts

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atomic absorption spectroscopy: radiation and light sources

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Choosing Light Sources for AAS Measurements

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atomic absorption spectroscopy: atomization methods

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Atomic Absorption Spectroscopy: Sample Atomization

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atomic absorption spectroscopy: interference

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

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atomic emission spectroscopy: overview

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atomic emission spectroscopy: instrumentation

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AES Sample Handling and Detection

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atomic emission spectroscopy: interference

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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

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ICP-AES Torch and Sample Analysis

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inductively coupled plasma atomic emission spectroscopy: instrumentation

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ICP-AES Instrument Types and Detection

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atomic emission spectroscopy: lab

Plasma Sources in Atomic Emission Spectroscopy

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atomic fluorescence spectroscopy

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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 spectral, chemical, and physical interference affect atomic absorption spectroscopy and how background correction helps improve accuracy.

Correcting Errors in Atomic Absorption Spectroscopy | JoVE K12

JoVE Core 分析化学 は、複雑な化学原理をアニメーションで視覚化することで、SI 単位から NMR 分光法を含むトピックをよりわかりやすくします。実験を撮影した実写動画では、これらの概念が世界中の研究所でどのように応用されているかを取り上げています。

analytical chemistry

Correcting Errors in Atomic Absorption Spectroscopy

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