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

AAS 측정은 검출된 분석물 신호의 크기를 모호하게 하거나 변경하는 스펙트럼, 화학적 또는 물리적 간섭에 직면할 수 있습니다.
스펙트럼 간섭은 간섭 물질 또는 분무 화염의 신호가 분석물의 신호와 겹쳐 분석물의 흡광도를 잘못 높이거나 마스킹할 때 발생합니다.
이 문제는 Zeeman, Smith-Hieftje 또는 중수소 배경 보정 기술을 사용하여 해결할 수 있습니다. 또한 고해상도 분광기는 중첩된 스펙트럼 라인으로 인한 스펙트럼 간섭을 최소화할 수 있습니다. 
화학적 간섭의 원인에는 매트릭스 성분과의 분석물 상호 작용이 포함되며, 이는 분무 효율을 낮추는 비휘발성 염을 생성합니다.
이러한 간섭은 높은 분무 온도를 사용하거나 착화 또는 방출제를 추가하여 방지할 수 있습니다.
또한 일부 원자 분석물은 분석 중에 이온화되어 흡수가 감소할 수 있습니다. 그러나 더 쉽게 이온화되는 원소를 추가하면 분석물의 이온화가 억제됩니다.
가스 유량 또는 화염 온도의 변화와 같은 비화학적 요인으로 인해 발생하는 물리적 간섭은 잦은 보정, 내부 표준물질 또는 샘플에 알려진 양의 분석물을 추가함으로써 최소화됩니다.

원자 흡수 분광법: 간섭

Atomic Absorption Spectroscopy: Interference

간섭은 분석 신호 또는 배경을 증가시키거나 감소시켜 원자 흡수(AA) 측정에서 체계적인 오류를 유발합니다. 이러한 간섭은 스펙트럼 간섭, 화학적 간섭 및 물리적 간섭의 세 가지 주요 범주로 그룹화할 수 있습니다.

스펙트럼 간섭은 다른 원소 또는 분자의 신호가 분석물 신호와 겹치면서 분석물의 흡광도를 잘못 높이거나 가릴 때 발생합니다. 이 간섭은 제이만, 스미스-아예프체 또는 중수소 배경 보정 방법을 사용하여 보정할 수 있습니다.

제이만 보정 방법은 자기장을 사용하여 흡수선을 세 개의 편광 구성 요소로 분할합니다. 두 개의 σ(이동)와 하나의 π(이동되지 않음). 분석물과 배경 흡광도는 자기장을 번갈아가며 개별적으로 측정하여 복잡한 행렬의 정확도를 높입니다.

스미스-아예프체 교정법은 고전류에서 중공 음극 램프(HCL)를 펄싱하여 방출선이 넓어지고 자체 반전을 겪게 하며, 이때 중앙 분석 선이 감소합니다. 이로 인해 선의 양쪽에서 강한 방출이 발생하여 배경에 흡수됩니다. 흡광도는 정상 및 고전류 조건에서 측정하여 분석물과 배경 신호를 구별할 수 있습니다. 단일 광원만 필요하지만 이 방법의 감도는 감소하며, 특히 자체 반전이 불충분하거나 회복이 너무 느릴 때 그렇습니다.

중수(D2) 배경 교정법은 D2 램프를 광범위 스펙트럼 광원으로 사용하여 원자 흡광 분광법(AAS)에서 배경 흡수를 교정합니다. 회전 거울은 협대역 중공 음극 램프(HCL)와 광대역 D2 램프 사이를 번갈아 가며 움직입니다. D2 램프는 넓은 파장 범위에서 배경 흡광도를 측정하는 반면, HCL은 특정 파장에서 분석물과 배경 흡광도를 측정합니다. 두 신호의 차이는 분석물 흡광도를 분리합니다. 저렴하지만 고정밀 측정에는 정밀도가 부족합니다.

또한 고해상도 분광기는 겹치는 스펙트럼 선으로 인한 스펙트럼 간섭을 최소화할 수 있습니다. 때로는 분석 전에 용매로 분석물을 반복적으로 추출할 수 있습니다.

화학적 간섭은 원치 않는 매트릭스 구성 요소가 분석물과 상호 작용하여 분무 효율이 감소할 때 발생합니다. 방출제 또는 착화제와 같은 화학적 개질제를 표본에 추가하여 분무를 향상시키거나 간섭 화합물의 형성을 방지할 수 있습니다. 일반적인 화학적 간섭에는 이온화 및 내화성 화합물 형성으로 인한 간섭이 있습니다.

분석물과 동일한 온도에서 이온화되는 원소 또는 화합물은 이온화를 변경할 수 있습니다. 이온화는 더 쉽게 이온화되는 원소가 포함된 용액을 과잉 첨가하여 분석물의 이온화를 억제함으로써 억제할 수 있습니다.

또한 분석물과 표본 매트릭스의 다른 종 간의 화학 반응은 쉽게 분무되지 않는 비휘발성 화합물을 형성할 수 있습니다. 이는 흡수를 위한 자유 원자의 형성을 방해합니다. 이러한 간섭은 화학적 경쟁자를 추가하거나 매우 높은 온도를 사용하여 방지합니다.

교정 표준은 실제 표본과 유사한 표본 매트릭스로 준비할 수 있으며, 이는 매트릭스에서 발생하는 화학적 간섭을 보상하는 데 도움이 됩니다.

가스 유량 변화 또는 화염 온도 변화와 같은 비화학적 요인에서 발생하는 물리적 간섭은 분무 또는 분무 프로세스에 영향을 미칩니다. 이러한 간섭은 내부 표준을 사용하거나 표본을 희석하여 해결할 수 있습니다. 표본 매트릭스를 수정하고 유사한 매트릭스로 교정 표준을 준비하면 물리적 간섭을 더욱 줄일 수 있습니다

간섭은 분석 신호 또는 배경을 강화하거나 감소시켜 원자 흡수(AA) 측정에서 체계적인 오류를 초래합니다. 이러한...

atomic-absorption-spectroscopy-interference

Education

교육

JoVE Core

Analytical Chemistry

분석 화학

Unit 1

제1단원

Atomic Spectroscopy

원자 분광법

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

correcting-errors-in-atomic-absorption-spectroscopy

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 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 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

analytical chemistry

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Correcting Errors in Atomic Absorption Spectroscopy

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