chemistry

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...

Troubleshooting a GC chromatograph can be made easier, if one learns to recognize the symptoms produced by an instrument malfunction, column and detector problems, leaks. Many symptoms appear as unusual peaks as shown below: Symptom: No peaks (Fig. 1)  Fig. 1: No peaks appear after the injection of the sample Possible Cause: Main power off, fuse burned out Action: Plug in the instrument, replace fuse Possible Cause: Detector off Action: Turn detector on and adjust its sensitivity Possible Cause: No carrier gas flow Action: Check the carrier gas lines and correct the problem i.e. replace empty gas cylinders, possible obstructed or broken gas lines Possible Cause: Injector temperature too low. The sample is not vaporized Action: Increase injector temperature. Possible Cause: Injector septum is leaking Action: Replace the septum. Possible Cause: The syringe used for the injection of sample is plugged up . Action: Clean the syringe or replace it if it is damaged. Possible Cause: Th...