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

Visible and Ultraviolet Light

Uv-Vis Spectrometer Double Beam Diffraction Grating Mirror 3 Mirror 2 Half Mirror Mirror 4 Reference Cuvette Sample 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 6b 7b 7a 5 I0 I

Uv-Vis Spectrometer Double Beam No 1a and 1 b The UV-Visible spectrophotometer uses two light sources, a deuterium (D2) 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

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 / Io where I is the light intensity after it passes through the sample and Io is the initial light intensity. The relation between A and T is: A = -log T = - log (I / Io) where A is the measured absorbance

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

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

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

Atomic Spectroscopy A method to analyze the elemental composition using atomic absorption or emission Energy transition electrons of atoms Absorption Emission E1 E1 v1 1 1 2 3 Excited State Excited State E2 E2 v2 2 E3 E3 v3 3  Ground State E0 Ground State Ej h = Ei– E0 i = 1.2 and 3 h = Ej – Ei i = 1.2 and 3

Atomic Absorption Spectroscopy Ej Beer Lambert Law : I0 I E0 Where : A = absorbance/Emission T = Transmitance Atomic Absorption Spectroscopy : The term used when the radiation absorbed by atoms is measured E0 and Ej : energy levels where Ej higher than E0. Arrow line: Absorption

Atomic Absorption Spectrometry Detector Output Atomized Sample (Flame) Lens Radiation Source Monochromator Flame Atomic Absorption Spectrometry AAS consist of two type: Flame AAS and Graphite-furnace AAS. Please open this link : http://www.cee.vt.edu/ewr/environmental/teach/smprimer/aa/aadiag.gif

Atomic Absorption Spectrometry 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 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.

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