Atomic Absorption Spectroscopy AASI Mentor Prof Kuniyuki KITAGAWA

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

Visible and Ultraviolet Light

g Uv-Vis Spectrometer Double Beam on G ra tin Light Source UV (Deuterium/D 2) cti Di ffr a 1 b Light Source Vis (Tungsten) 3 Detector-2 Filter Reference Beam i M Mirror 1 Slit 2 r 4 o rr 1 a 2 6 a Reference Cuvette 7 a I Lens 1 Half Mirror 5 4 2 r rro M irr 6 b or 3 Mi Detector-1 Sample Beam Sample Cuvette 7 b Lens 2 I 0

Uv-Vis Spectrometer Double Beam • • No 1 a 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 6 a and 6 b No 6 a and 6 b – Half of the light is reflected (6 a), the other half passes through (6 b) No 7 a – One of the beams is allowed to pass through a reference cuvette. No 7 b – 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 E 1 E 2 E 3 Ground State h = Ei– E 0 i = 1. 2 and 3 E 0 Emission Excited State Absorption E 1 E 2 E 3 Ground State h = Ej – Ei i = 1. 2 and 3 Ej v 1 1 v 2 2 v 3 3 1 2 3

Atomic Absorption Spectroscopy Ej I 0 E 0 Beer Lambert Law : I Where : A = absorbance/Emission T = Transmitance 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

Atomic Absorption Spectrometry Radiation Source Lens Atomized Sample (Flame) Lens Monochromator Detector Output 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 hightemperature 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