Analysis of Salts: Difference between revisions
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With micro-chemical reactions, a salt analysis can be performed on very small samples. Usually this is done using a microscope (polarizing microscope). This method can also be quite convenient locally at the object. The micro-chemical analysis of salt consists in the qualitative detection of individual salt ions in more or less concentrated aqueous solution. | With micro-chemical reactions, a salt analysis can be performed on very small samples. Usually this is done using a microscope (polarizing microscope). This method can also be quite convenient locally at the object. The micro-chemical analysis of salt consists in the qualitative detection of individual salt ions in more or less concentrated aqueous solution. | ||
== [[X-Ray | == [[X-Ray Diffraction analysis (XRD)]] == | ||
With the XRD analysis, qualitative and quantitative salt analyses are carried out. When X-rays hit a crystalline material a series of "reflections" are produces which are characteristic for each phase like a "fingerprint". It is a laboratory method and the amount of the sample can be quite small with special sample holders. | With the XRD analysis, qualitative and quantitative salt analyses are carried out. When X-rays hit a crystalline material a series of "reflections" are produces which are characteristic for each phase like a "fingerprint". It is a laboratory method and the amount of the sample can be quite small with special sample holders. | ||
Revision as of 08:27, 17 August 2011
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Author: Hans-Jürgen Schwarz
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Abstract[edit]
In the presence of a salt load or visible salt damage, a wide variety of methods are used. The methods are presented that usually allow a quantitative determination of the salt-forming ions, or at least a qualitative determination of individual ions or salt phases. The measuring principle, the application and the advantages of each method are briefly outlined.
Mikroscopy[edit]
With the help of the polarizing microscope, the various salts are determined based on their optical properties. This includes in particular the study of the birefringence and light refraction of the salts. Compared to normal by light microscopy the polarizing microscope has two polarizers - the polarizer and the analyzer. The analyzer is used to recognize the optical properties of a salt by the change of the linearly polarized light due to the salt.
Microchemistry[edit]
With micro-chemical reactions, a salt analysis can be performed on very small samples. Usually this is done using a microscope (polarizing microscope). This method can also be quite convenient locally at the object. The micro-chemical analysis of salt consists in the qualitative detection of individual salt ions in more or less concentrated aqueous solution.
X-Ray Diffraction analysis (XRD)[edit]
With the XRD analysis, qualitative and quantitative salt analyses are carried out. When X-rays hit a crystalline material a series of "reflections" are produces which are characteristic for each phase like a "fingerprint". It is a laboratory method and the amount of the sample can be quite small with special sample holders.
Atomabsorptionspectroskopy (AAS)[edit]
The atomic absorption spectroscopy is a method that allows rapid and accurate quantitative determinations of many elements. Since the method relies on the energy absorption by free atoms, it can usually be used without prior separation or isolation steps of other elements present in the sample. The quantity of sample needed for analysis is low. Element concentrations of a millionth (ppm) or one billionth part (ppb) of the sample can be detected.
Induktiv gekoppeltes Plasma (ICP)[edit]
Das ICP dient zur Anregung z.B. bei der Atomemissionsspektroskopie (AES-ICP) oder in der Kopplung mit einem Massenspektrometer (ICP-MS). Das induktiv gekoppelte Plasma ist ein im Hochfrequenzfeld (27 MHz) ionisiertes Gas (Argon), das als Atomisierungs- und Anregungsmedium für die eingesprühte, flüssige oder gelöste Probe dient. Das ICP kann in der Emissions-Spektroskopie mit verschiedenen optischen und elektrischen Systemen entweder mit simultanen oder sequentiellen Multielement-Spektrometern kombiniert werden. Es lassen sich damit sehr geringe Konzentrationen in Größenordnungen von einem millionstel (ppm) oder einem milliardstel Teil (ppb) in der Probe nachweisen.
Ionchromatography (IC)[edit]
Unter Chromatographie versteht man ganz allgemein Verfahren zur Trennung von Substanzen, wobei diese unterschiedlich zwischen einer stationären und einer mobilen Phase verteilt werden. Bei der Ionenchromatographie werden aufgrund ihrer Ladungen Ionen an der stationären Phase gebunden und später durch einen Eluenten durch einen Ionenaustausch in die mobile Phase frei gegeben. Die Quantifizierung geschieht mit Hilfe eines geeigneten Detektors. Unter Nutzung spezifischer Trennsäulen können sowohl Anionen wie auch Kationen quatitativ in geringer Konzentration bestimmt werden.
Photometry[edit]
Das Grundprinzip der Photometrie besteht darin, eine farbige bzw. lichtabsorbierende Lösung herzustellen, wobei der gesuchte Stoff oder das gesuchte Element in eine lichtechte, farbige und lösliche Verbindung eingebaut oder überführt wird oder eine Farbreaktion auslöst bzw. steuert. Die Photometrie beruht dabei auf der Messung der Absorption monochromatischer Strahlung durch die Lösung. Es sind damit quantitative Analysen von Anionen und Kationenin in einer für die Salzanalytik ausreichenden Genauigkeit möglich.