4 Uv-Vis Spectrometer Double Beam No 1a and 1 bThe 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 2The grating is able to rotated so a specific wavelength is selectable. From diffraction grating goes to slit 2 and filter (No. 3)No 3A filter is used to remove unwanted higher orders of diffraction.No 4The light beam hits a second mirrorNo 5splited by a half mirror to 6a and 6bNo 6a and 6bHalf of the light is reflected (6a), the other half passes through (6b)No 7aOne of the beams is allowed to pass through a reference cuvette.No 7bthe other passes through the sample cuvette. The intensities of the light beams are then measured at the end
5 Beer-Lambert LawThe 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
6 TransmittanceThe 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
9 Atomic SpectroscopyA method to analyze the elemental composition using atomic absorption or emissionEnergy transition electrons of atomsAbsorptionEmissionE1E1v11123Excited StateExcited StateE2E2v22E3E3v33Ground StateE0Ground StateEjh = Ei– E0i = 1.2 and 3h = Ej – Eii = 1.2 and 3
10 Atomic Absorption Spectroscopy EjBeer Lambert Law :I0IE0Where :A = absorbance/EmissionT = TransmitanceAtomic Absorption Spectroscopy :The term used when the radiation absorbed by atoms is measuredE0 and Ej : energy levels where Ej higher than E0.Arrow line: Absorption
11 Atomic Absorption Spectrometry DetectorOutputAtomized Sample(Flame)LensRadiation SourceMonochromatorFlame Atomic Absorption SpectrometryAAS consist of two type: Flame AAS and Graphite-furnace AAS.Please open this link :
12 Atomic Absorption Spectrometry Radiation SourceHollow-Cathode LampAtomization SampleAAS 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.
13 Atomic Absorption Spectrometry Monochromator and DetectorAA spectrometers use monochromators and detectors for UV and visible light.Monochromator is used to isolate the absorption line from background light due to interferences.
14 AssignmentExplain 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