Name: preparing complex samples for analysis
Uploaded: 2024-12-05T18:31:55.000Z
Duration: 1 min 8 s
Channel: JoVE

İnorganik analiz için numune hazırlama yöntemleri, malzemenin özelliklerine bağlıdır.
Suda çözünmeyen birçok inorganik madde, güçlü mineral asitler kullanılarak çözündürülebilir. Hala çözünmemişlerse, füzyon tekniği olarak bilinen daha yoğun bir yöntem kullanılır.
Burada numune tartılır ve yaklaşık 1 ila 10 veya 20 oranında bir akı malzemesi ile karıştırılır. Numune akışı karışımı, erimiş bir karışım elde etmek için bir platin pota içinde ısıtılır. Soğuduktan sonra bu, suda veya seyreltik asitte çözünür yeni bir malzeme elde etmek üzere katılaşır.
Buna karşılık, organik maddeler kuru külleme ve ıslak sindirim yöntemleriyle ayrıştırılır. Kuru küllemede, numune atmosferik oksijenli bir kül fırınında ısıtılır. Burada, organik materyalin yanması, daha fazla analiz için inorganik bir kalıntı oluşturur.
Islak sindirim, organik materyali parçalamak için bir asit karışımı kullanır.

analiz İçin numune hazırlama: gelişmiş teknikler

Karmaşık numunelerin doğru analizi, güvenilir ve tekrarlanabilir sonuçlar elde etmek için genellikle gelişmiş hazırlama teknikleri gerektirir. İnorganik veya organik maddeler içeren numunelerin etkili bir şekilde çözülmesi veya ayrıştırılması zor olabilir. Standart numune hazırlama yöntemleri arasında asit ile parçalama, füzyon, kuru külleme ve ıslak parçalama bulunur.

Güçlü asitlerle asit sindirimi, suda çözünmeyen inorganik maddeleri çözmek için yaygın olarak kullanılır. Bu yöntem, toprak veya mineral numunelerini analiz etmek için yararlı olabilir. Asit sindirimi sırasında, çözünmeyen katı numune, yüzey alanını artırmak için ince öğütülür veya ezilir, bu da asitlerle daha etkili bir reaksiyona olanak tanır. Yaygın olarak kullanılan asitler arasında hidroklorik asit, nitrik asit, sülfürik asit ve aqua regia (nitrik ve hidroklorik asit karışımı) bulunur. Her asit, farklı numune tipleri için belirli avantajları sağlar.

<ul style="list-style-type: disc; display: flex; flex-direction: column; gap: 10px; padding: 0 0 0 40px;">
 <li>Hidroklorik asit (HCl), genellikle klorürleri, oksitleri ve karbonatları çözmek için kullanılır ve metaller ve cevherler gibi malzemeler üzerinde de etkilidir. • Nitrik asit (HNO_3), organik maddeleri parçalamak ve metalleri oksitlemek için mükemmeldir ve bu da onu biyolojik dokular veya metal analizleri için yaygın bir seçim haline getirir.
 </li>
 <li>Sülfürik asit (H_2SO_4), örneğin sülfürler veya metaller gibi daha dirençli numuneleri çözerken güçlü bir su giderici maddeye ihtiyaç duyulduğunda kullanılır.
 </li>
 <li>Nitrik ve hidroklorik asitlerin bir karışımı olan Aqua regia, özellikle tek tek asitlere dirençli olan altın ve platin gibi asil metalleri çözmek için etkilidir.
 </li>
</ul>
Numune, uygun bir kapta seçilen güçlü asitle işlenir ve burada çözünür formlara veya iyonlara parçalanır. Parçalanma sürecini hızlandırmak için ısı da uygulanabilir. Parçalanmadan sonra, suyla seyreltilmiş elde edilen karışım daha fazla analiz için uygundur.

Füzyon tekniği, asit sindirimi ile çözünür bir forma parçalanamayan inorganik maddeleri çözmek için alternatif bir yöntemdir. Burada, ağırlıklı numune, tipik olarak yaklaşık 1 ila 10 veya 20 oranında belirli bir oranda bir flux malzemesiyle karıştırılır. Numune-flux karışımı, yüksek sıcaklıklara ve kimyasal reaksiyonlara dayanıklı bir platin lehim kabına yerleştirilir. Bu lehim kabı, erimiş bir karışım elde etmek için yüksek sıcaklıklı bir fırında ısıtılır. Isıtmadan sonra, erimiş karışımın suda veya seyreltik asitte çözünebilen yeni bir madde elde edilene kadar soğuması sağlanır.

Katı ve sıvı bileşikleri çözmek için numune hazırlamada flux kullanımına ilişkin birkaç örnek şunlardır:

<ul style="list-style-type: disc; display: flex; flex-direction: column; gap: 10px; padding: 0 0 0 40px;">
 <li>Demir ve Krom Alaşımları için flux Olarak Na_2CO_3 ve Na_2O_2: Sodyum karbonat (Na_2CO_3) yaygın olarak kullanılan bir flux olsa da, bazı durumlarda daha güçlü oksitleme kabiliyeti nedeniyle sodyum peroksit (Na_2O_2) kullanılır. Bu kombinasyon, özellikle nikel potadaki demir ve krom alaşımlarını çözmek için faydalıdır. 
 </li>
 <li>Hızlı Çözünme için Li_2B_4O_7 ve Li_2SO_4 Karışımı: Ağırlıkça 2:1 oranında lityum tetraborat (Li_2B_4O_7) ve lityum sülfat (Li_2SO_4) karışımı, refrakter silikatları ve oksitleri çözmedeki hızlı yeteneği nedeniyle vurgulanır.
 </li>
</ul>
Kuru külleme ve ıslak parçalama yöntemleri, organik maddeleri ayrıştırmak için yaygın olarak kullanılır. Kuru küllemede, organik numune yüksek sıcaklıkta bir mufla fırınında ısıtılır. Isı, atmosferik oksijenin varlığında organik materyalin yanmasına neden olur ve geride inorganik bir kalıntı veya 'kül' bırakır. Bu kül daha sonra daha ileri analiz için uygun bir çözücüde çözülebilir. Islak parçalama, organik materyali parçalamak için asitlerin kullanılmasını içerir.

Analiz İçin Numune Hazırlama: Gelişmiş Teknikler

Karmaşık numunelerin doğru analizi, güvenilir ve tekrarlanabilir sonuçlar elde etmek için genellikle gelişmiş hazırlama teknikleri gerektirir. İçeren örnekler ...

sample-preparation-for-analysis-advanced-techniques

Education

JoVE Core

Analytical Chemistry

Analitik Kimya

Unit 1

Ünite 1

Method Development and Sampling Techniques

Yöntem Geliştirme ve Örnekleme Teknikleri

method-development-and-sampling-techniques

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

Sample Preparation for Analysis: Advanced Techniques

preparing complex samples for analysis

Preparing complex samples for analysis often requires special digestion and fusion methods. Samples with inorganic or organic material can be hard to dissolve or break down. Common sample preparation methods include acid digestion, fusion, dry ashing, and wet digestion. These steps help turn difficult samples into forms that can be tested reliably and again with similar results.

Acid digestion is often used for inorganic materials that do not dissolve in water. It is useful for soil and mineral samples. The solid sample is first finely ground or crushed to increase surface area, which helps it react better with the acid. Common acids include hydrochloric acid, nitric acid, sulfuric acid, and aqua regia, which is a mixture of nitric and hydrochloric acids.

Each acid has a different use. Hydrochloric acid, or HCl, is often used for chlorides, oxides, and carbonates, and it also works on metals and ores. Nitric acid, or HNO3, is good for breaking down organic matter and oxidizing metals, so it is often used for biological tissues or metal analysis. Sulfuric acid, or H2SO4, is useful when a strong dehydrating agent is needed, such as for more resistant sulfides or metals. Aqua regia is especially effective for noble metals like gold and platinum, which resist individual acids.

During digestion, the sample is placed in a suitable container and treated with the chosen strong acid. Heat may be added to speed up the process. The sample changes into soluble forms or ions, and the final mixture is diluted with water before further analysis. Fusion is another way to dissolve inorganic materials when acid digestion is not enough. In this method, the weighed sample is mixed with a flux in a ratio of about 1 to 10 or 20, then heated in a platinum crucible in a high-temperature furnace until it melts.

After cooling, the fused material becomes soluble in water or dilute acid. Some flux examples are sodium carbonate and sodium peroxide for iron and chromium alloys in a nickel crucible. Potassium disulfate, K2S2O7, works well for refractory oxides and can be made by heating potassium hydrogen sulfate to remove foaming byproducts. A mixture of lithium tetraborate and lithium sulfate in a 2:1 ratio is also used because it dissolves refractory silicates and oxides quickly.

Organic samples are often prepared by dry ashing or wet digestion. In dry ashing, the sample is heated in a muffle furnace at high temperature. The organic material burns in air and leaves behind an inorganic residue called ash. That ash can then be dissolved in a suitable solvent for analysis. Wet digestion also breaks down organic material, but it does so with acids.

Preparing Complex Samples for Analysis

development of analytical methods

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How Analytical Methods Are Checked

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Classical and Instrumental Sample ID

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quantitative analysis

Measuring Analyte Concentration

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Calibrating Lab Instruments for Accurate Results

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Choosing Samples for Reliable Results

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sample preparation for analysis: advanced techniques

Preparing complex samples for analysis often requires special digestion and fusion methods. Samples with inorganic or organic material can be hard to dissolve or break down. Common sample preparation methods include acid digestion, fusion, dry ashing, and wet digestion. These steps help turn difficult samples into forms that can be tested reliably and again with similar results. Acid digestion is often used for inorganic materials that do not dissolve in water. It is useful for soil and...

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Sampling Errors in Sample Preparation

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key terms and concepts

Learn how acid digestion, fusion, dry ashing, and wet digestion prepare complex samples for analysis, including soil, minerals, metals, and organic tissue.

Preparing Complex Samples for Analysis | JoVE K12

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analytical chemistry

Preparing Complex Samples for Analysis

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