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

AAS genellikle numuneleri alev veya elektrotermal atomizasyon yoluyla atomize eder.
Alev atomizasyonu tipik olarak numuneyi sürekli olarak aerosol haline getirmek için bir nebulizatör ve yakıt ve oksidan ile karıştırmak için bir püskürtme odası düzeneği kullanır.
Aerosol damlacıklarının sadece yaklaşık yüzde beşi aleve ulaşacak kadar incedir, burada birincil yanma bölgesinde çözülürler ve iç alevde atomize olan çıplak parçacıkları geride bırakırlar.
Gaz halindeki atomlar, iyonlar ve moleküler türler, analiz için bölgeler arası bölgeden hızla akar ve alevden dışarı çıkar.
Numunenin çok azı başarılı bir şekilde atomize edildiğinden ve tespit edildiğinden, alev atomizasyonu düşük analit konsantrasyonlarına veya sınırlı hacimlere sahip numuneler için iyi değildir.
Öte yandan, grafit fırın atomizasyonu olarak da bilinen elektrotermal atomizasyon, yüksek sıcaklıklarda kurutulan, kömürleştirilen ve atomize edilen küçük, ayrı numunelerden analitleri yakalamak ve konsantre etmek için bir grafit tüp kullanır.
Alternatif olarak, daha hafif kimyasal koşullar altında bazı elementler önce uçucu hidrit ürünlerine dönüşür ve daha sonra atomize edilebilir. Ek olarak, cıva tayini, doğal uçuculuğu nedeniyle benzersiz bir soğuk buhar yöntemi kullanabilir.

atomik absorpsiyon spektroskopisi: atomizasyon yöntemleri

Atomic Absorption Spectroscopy: Atomization Methods

Atomik Absorpsiyon Spektroskopisi (AAS), numuneleri alev atomizasyonu ya da elektrotermal atomizasyon yoluyla atomize eder. Alev atomizasyonu genellikle bir nebülizör ve püskürtme odası montajı içerir; bu montaj, numuneyi yakıt-oksidan karışımıyla birleştirir ve ince bir aerosol oluşturur, bu aerosol daha sonra bir fırına girer. Genellikle, yakıt ve oksidan, yaklaşık stokiyometrik bir oranda birleştirilir. Ancak, kolayca oksitlenen atomlar için yakıt açısından zengin bir karışım daha avantajlı olabilir. Aerosol damlacıklarının yalnızca yaklaşık %5'i aleve ulaşır, burada birincil yanma bölgesinde çözünürlüklerini kaybeder ve geriye çıplak partiküller kalır; bu partiküller iç alevde atomize olur. Gaz fazındaki atomlar, iyonlar ve moleküler türler, analiz için hızlı bir şekilde bölgesel alanlardan geçer ve alevden dışarı çıkar. Alev atomizatörleri, büyük aerosol damlacıklarının aleve ulaşamaması ve yanma gazlarından dolayı önemli ölçüde numune seyrelmesi nedeniyle düşük atomizasyon verimliliğine sahiptir. Ancak, alev atomizasyonu verimliliği, numunenin sürekli olarak aspirasyonunu sağlamak, yakıt-oksidan oranlarını optimize etmek, nebülizatör akış hızlarını ayarlamak ve fırın yüksekliğini ayarlamak suretiyle artırılabilir.

Alev atomizasyonu, düşük analit konsantrasyonlarına sahip veya sınırlı hacimli numuneler için uygun değildir, çünkü başarıyla atomize edilen ve tespit edilen numune miktarı çok azdır. Buna karşın, elektrotermal atomizasyon, diğer adıyla grafit fırın atomizasyonu, analitleri yakalamak ve yoğunlaştırmak için bir grafit tüpü kullanır ve küçük, belirli numuneler için iyi sonuçlar verir. Bu teknikte, numune yüksek sıcaklıklarda atomize edilmeden önce kurutulur ve kömürleştirilir.

As, Se, Sb, Bi, Ge, Sn, Te ve Pb gibi elementler, daha kolay koşullar altında önce uçucu hidrürlere kimyasal olarak dönüştürülerek alevin içine taşınabilir ve atomize edilebilir. Ayrıca, cıva belirlemesi, doğal uçuculuğu nedeniyle benzersiz bir soğuk buhar yöntemi kullanarak yapılabilir.

Atomik Absorpsiyon Spektroskopisi: Atomizasyon Yöntemleri

Atomik Absorpsiyon Spektroskopisi (AAS), numuneleri alev atomizasyonu veya elektrotermal atomizasyon yoluyla atomize eder. Alev atomizasyonu tipik olarak bir ...

atomic-absorption-spectroscopy-atomization-methods

Education

JoVE Core

Analytical Chemistry

Analitik Kimya

Unit 1

Ünite 1

Atomic Spectroscopy

Atomik Spektroskopi

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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 fuel-rich mixture can work better for atoms that oxidize easily.

Only about 5% of the aerosol droplets reach the flame. In the primary combustion zone, these droplets undergo desolvation, which means the solvent is removed. The bare particles are then atomized in the inner flame. The gaseous atoms, ions, and molecular species move through the interzonal region for analysis before leaving the flame.

Flame atomizers have low atomization efficiency. Large droplets do not reach the flame, and combustion gases also dilute the sample. Efficiency can be improved by continuously aspirating the sample, adjusting the fuel-to-oxidant ratio, changing the nebulizer flow rate, and setting the burner height. Flame atomization is not a good choice for samples with very low analyte levels or small sample volumes.

Electrothermal atomization, also called graphite furnace atomization, uses a graphite tube to collect and concentrate the analytes. It works well for small, discrete samples. The sample is first dried and charred, then atomized at very high temperatures.

Some elements, including As, Se, Sb, Bi, Ge, Sn, Te, and Pb, can be handled under milder conditions by forming volatile hydrides before they are carried to the flame. Mercury can also be measured with a cold-vapor method because it is naturally volatile.

Atomic Absorption Spectroscopy: Sample Atomization

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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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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 (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...

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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

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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 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

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Correcting Errors in Atomic Absorption Spectroscopy

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atomic absorption spectroscopy: lab

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atomic emission spectroscopy: interference

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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

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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...

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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 AAS atomizes samples with flame and graphite furnace methods, plus hydride and cold-vapor techniques for specific elements.

Atomic Absorption Spectroscopy: Sample Atomization | JoVE K12

JoVE Core Analitik Kimya, karmaşık kimyasal prensiplerini anlaşılır, ilgi çekici animasyonlara dönüştürerek basitleştirir ve SI Birimlerinden NMR spektroskopisine kadar konuları daha erişilebilir ve anlaşılır hale getirir. Buna ek olarak, bilim insanlarının yer aldığı videolar, bu kavramların dünya çapındaki laboratuvarlarda yürütülen gerçek dünya araştırmalarındaki uygulamalarını gösterir.

analytical chemistry

Atomic Absorption Spectroscopy: Sample Atomization

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