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Atomic Absorption Spectroscopy (AAS)I Mentor : Prof. Kuniyuki KITAGAWA Assistant: Dr. Eng.Nelfa Desmira.

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Presentation on theme: "Atomic Absorption Spectroscopy (AAS)I Mentor : Prof. Kuniyuki KITAGAWA Assistant: Dr. Eng.Nelfa Desmira."— Presentation transcript:

1 Atomic Absorption Spectroscopy (AAS)I Mentor : Prof. Kuniyuki KITAGAWA Assistant: Dr. Eng.Nelfa Desmira

2 Visible and Ultraviolet Light

3 Uv-Vis Spectrometer Double Beam I0I0 I Diffraction Grating Mirror 3 Mirror 2 Half Mirror Mirror 4 Reference Cuvette Sample Cuvette Filter Mirror 1 Light Source Vis (Tungsten) Light Source UV (Deuterium/D2) Slit 1 Slit 2 Lens 1 Lens 2 Detector-1 Detector-2 Reference Beam Sample Beam 1a 1b 2 3 4 6a 6b7b 7a 5

4 Uv-Vis Spectrometer Double Beam No 1a and 1 b – The UV-Visible spectrophotometer uses two light sources, a deuterium (D 2 ) lamp for ultraviolet light and a tungsten (W) lamp for visible light. Two light sources hit Mirror 1 one pass through slit 1 go to diffraction grating (no.2) No 2 – The grating is able to rotated so a specific wavelength is selectable. From diffraction grating goes to slit 2 and filter (No. 3) No 3 – A filter is used to remove unwanted higher orders of diffraction. No 4 – The light beam hits a second mirror No 5 – splited by a half mirror to 6a and 6b No 6a and 6b – Half of the light is reflected (6a), the other half passes through (6b) No 7a – One of the beams is allowed to pass through a reference cuvette. No 7b – the other passes through the sample cuvette. The intensities of the light beams are then measured at the end

5 Beer-Lambert Law The Beer-Lambert law is the linear relationship between absorbance and concentration of an absorbing species. Experimental measurements are usually made in terms of transmittance (T), which is defined as: T = I / I o where I is the light intensity after it passes through the sample and I o is the initial light intensity. The relation between A and T is: A = -log T = - log (I / I o ) where A is the measured absorbance

6 Transmittance The relationship between absorbance and transmittance is illustrated in the following diagram:

7 Assignment Calculate the transmission for absorbance A 0.6 and 0.06 How to make correction for background absorption caused by sample matrices using a one-beam spectrophotometer? Explain the system of single beam Uv-Vis Spectrometer

8 Atomic Absorption Spectroscopy (AAS) II Mentor : Prof. Kuniyuki Kitagawa Assistant : Dr. Eng. Nelfa Desmira

9 Atomic Spectroscopy A method to analyze the elemental composition using atomic absorption or emission Energy transition electrons of atoms Ground State Excited State AbsorptionEmission 1 2 3 v1v1 v2v2 v3v3 1 2 3 E1E1 E2E2 E3E3 EjEj h = Ej – E i i = 1.2 and 3 E1E1 E2E2 E3E3 h = Ei– E 0 i = 1.2 and 3 E0E0

10 Atomic Absorption Spectroscopy Atomic Absorption Spectroscopy : The term used when the radiation absorbed by atoms is measured E 0 and Ej : energy levels where Ej higher than E 0. Arrow line: Absorption E0E0 EjEj Beer Lambert Law : Where : A = absorbance/Emission T = Transmitance I0I0 I

11 Atomic Absorption Spectrometry Flame Atomic Absorption Spectrometry AAS consist of two type: Flame AAS and Graphite-furnace AAS. Please open this link : Detector Output Atomized Sample (Flame) Lens Radiation Source Monochromator

12 Radiation Source – Hollow-Cathode Lamp Atomization Sample – AAS analyzes atoms in gas phase so atoms in a sample must heated/vaporized in a high- temperature source such as a flame or graphite furnace. Flame AA is suitable to analyze solutions, while graphite furnace AA is able to analyze solutions, slurries, or solid samples. Atomic Absorption Spectrometry

13 Monochromator and Detector – AA spectrometers use monochromators and detectors for UV and visible light. – Monochromator is used to isolate the absorption line from background light due to interferences. Atomic Absorption Spectrometry

14 Assignment Explain the detail of flame atomization absorption spectrometry (FAAS) Explain the detail of graphite furnace atomization absorption spectrometry (GAAS) Compare the detection limits of FAAS and GAAS and mention their applications respectively

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