chemistry

Atomic Absorption Home > Analytical Chemistry > Atomic Absorption ATOMIC ABSORPTION Atomic Absorption Spectrometry (AAS) Sampling Techniques for Atomic Absorption Spectrometry Light sources for atomic absorption     Quantitative Analysis by Atomic Absorption       Advantages and Disadvantages of Atomic Absorption Spectrometry and Graphite Furnace       Atomic absorption spectrometry (AAS) is an analytical technique that measures the concentration of an element by measuring the amount of light (intensity of light) that is absorbed - at a characteristic wavelength - when it passes through a cloud of atoms of this element. As the number of atoms in the light path increases, the amount of light absorbed increases in a predictable way. Modern atomic absorption spectrometry was introduced in 1955 as ...

Advantages and Disadvantages of Atomic Absorption Spectrometry and Graphite Furnace Home > Analytical Chemistry > Analytical Chemistry - Atomic Absorption > Atomic Absorption Spectrometry (AAS) > Advantages and Disadvantages of Atomic Absorption Spectrometry and Graphite Furnace   Advantages and Disadvantages of Atomic Absorption Spectrometry and Graphite Furnace Atomic Absorption Spectrometry (AAS) is an analytical technique that measures the concentration of an element by measuring the amount of light (intensity of light) that is absorbed - at a characteristic wavelength - when it passes through a cloud of atoms of this element. As the number of atoms in the light path increases, the amount of light absorbed increases in a predictable way. The main advantages of AAS   are given below: High sample throughput Easy to use High precision Inexpensive technique The main disadvantages of  AAS...

Sampling Techniques for Atomic Absorption Spectrometry Home > Analytical Chemistry > Analytical Chemistry - Atomic Absorption > Atomic Absorption Spectrometry (AAS) > Sampling Techniques for Atomic Absorption Spectrometry Sampling Techniques for Atomic Absorption Spectrometry   Two systems are commonly used to produce atoms from the sample in atomic absorption spectrometry : Aspiration & electrothermal atomization (graphite furnace).   Aspiration involves sucking a solution of the sample into a flame. Figure I.1 shows a typical burner and spray chamber. Ethylene/air or ethylene /dinitrogen oxide are used. A flexible capillary tube connects the solution to the nebulizer. At the tip of the capillary, the solution is “nebulized” that means is broken into small drops. The larger drops fall out and drain off while smaller ones vaporize in the flame. Only 1% of the sample is nebulized...

Light sources for atomic absorption Home > Analytical Chemistry > Analytical Chemistry - Atomic Absorption > Atomic Absorption Spectrometry (AAS) > Light sources for atomic absorption Light sources for atomic absorption It is well known that an atom in its ground state absorbs light at discrete wavelengths (E = h*c/λ). In order to measure this narrow light absorption with maximum sensitivity, it is necessary to use a line source, which emits the specific wavelengths which can be absorbed by the atom. Narrow line sources not only provide high sensitivity, but also make atomic absorption a very specific analytical technique. The two most common line sources used in atomic absorption are the “ hollow cathode lamp, HCL ” and the “ electrodeless discharge lamp, EDL ”.   The Hollow Cathode Lamp HCL The common source of light is a “ hollow cathode lamp ”. This contains a t...

Quantitative Analysis by Atomic Absorption Home > Analytical Chemistry > Analytical Chemistry - Atomic Absorption > Atomic Absorption Spectrometry (AAS) > Light Sources for Atomic Absorption > Quantitative Analysis by Atomic Absorption   Quantitative Analysis by Atomic Absorption   The capability of an atom to absorb very specific wavelengths of light is utilized in atomic absorption spectrometry . Light of a specific wavelength and of initial intensity I o is focused on the flame cell containing ground state atoms. The initial light intensity is decreased by an amount determined by the atom concentration in the flame cell. The light is then directed to the detector where the reduced intensity, I t , is measured. The amount of light absorbed is determined by comparing I t   to I o and according to Beer’s law :   A = log I o / I t = α * c * d         (1)   Abso...

Atomic Absorption Spectrometry (AAS) Home > Analytical Chemistry > Analytical Chemistry - Atomic Absorption > Atomic Absorption Spectrometry (AAS) Atomic Absorption Spectrometry (AAS)   Atomic absorption spectrometry (AAS) is an analytical technique that measures the concentration of an element by measuring the amount of light (intensity of light) that is absorbed - at a characteristic wavelength - when it passes through a cloud of atoms of this element. As the number of atoms in the light path increases, the amount of light absorbed increases in a predictable way.   History of Atomic Absorption Spectrometry The phenomenon of light absorption had already been investigated at the beginning of the 18th century. It was observed that the original radiation intensity is resolved into three components: into reflected, transmitted and absorbed radiation. The two fundamental laws governing the fraction...