AES

Atomic emission spectroscopy: 

Atomic emission spectroscopy Presented By: Devanshi soni 1 st sem- pharmaceutics-M.pharm Guided By: Mr. Nishit Patel M.Pharm in Q.A. Dharmaj Degree Pharmacy College.

Slide 2: 

n = 1 n = 2 n = 3 Ground state Excited state

Slide 3: 

n = 1 e n = 2 n = 3 electron hv ← ↑ ↓ → energy

Slide 4: 

n = 1 n = 2 n = 3 ↑ ↓ → ← e Transition An Excited electron is Unstable, must do what?

Slide 5: 

n = 1 n = 2 n = 3 e Drops to Ground State Emits a “Photon” of Light

Principle: 

Principle Emission spectroscopy mainly based on the measurement of intensity of light emitted when metal is introduced in to excitation source. The wavelength of the color tells us what the element is and the intensity of color tells us how much of the element is present.

Example:: 

Example:

Excitation Paths: 

Excitation Paths Flame: Possible to analyze multiple component simultaneously Relatively low temperature Routine analysis of alkali and alkaline-earth metals Arc and Spark: Handle liquid or solid samples Requires frequent replacement of electrodes Plasma: Hotter source Plasma sources allow for wider range of elements

Instrumentation:: 

Instrumentation: Excitation source Electrodes : Self and graphite electrode. Sample holder : Solid and liquid sample holder. Monochromators: Prism, grating, echelle. Slits Detectors: Photomultipliers and photographic. Read out unit

Flame emission spectroscopy:: 

Flame emission spectroscopy: The temperature of the flame which is primarily responsible for the occurrence of the above mentioned processes is controlled by several factors which are , Type of fuel and oxidant & fuel to oxidant ratio. Type of solvent for preparing the sample solution Amount of solvent which is entering in to the flame Type of burner employed in flame photometer Particular region in flame which is to be focused in to the entrance slit

Process Generating Atomic Emission in Flame : 

Process Generating Atomic Emission in Flame Liquid sample enters nebulizer → small droplets of liquid enters in the flame→ evaporation of droplets→ formation of fine solid particles→ decomposition of particles to free atoms →Formation of excited atoms and emission of radiation from atoms as relaxation occurs→ oxidation of atoms.

Burners: : 

Burners: Mecker burner This burner was used earlier & employed neutral gas and oxygen. As this burner produced relatively low temperatures & low excitation energies this was generally used for the alkali metals. It produce chemically non-homogeneous flame.

2. Total consumption burner : 

2. Total consumption burner Produce noisy and turbulent flame.

3. Premix or laminar flow burner : 

3. Premix or laminar flow burner 5% droplets reached to flame. Not used when 2 solvents are employed.

4. Lundergraph burner : 

4. Lundergraph burner

5. Shielded burner: 

5. Shielded burner In this the flame was shielded from ambient atmosphere by a stream of inert gas. This shielding leads to a quieter flame and better analytical sensitivity.

Plasma emission spectroscopy: 

Plasma emission spectroscopy Plasma – An electrically neutral, highly ionized gas composed of ions, electrons, and neutral particles. It is a phase of matter distinct from solids, liquids, and normal gases.

Three types of high-temperature plasmas: 

Three types of high-temperature plasmas The inductively coupled plasma (ICP). The direct current plasma (DCP). The microwave induced plasma (MIP). The most important of these plasmas is the inductively coupled plasma (ICP).

ICP: 

Inductively Coupled Plasma (ICP) Plasma generated in a device called a Torch 3 quartz tubes 2.5 c.m. At the top water cooled induction coil powered by radiofrequency generator. Telsa coil produces initiation spark & ionization of gas. Ions and e- interact with magnetic field and begin to flow in a circular motion. Resistance to movement (collisions of e- and cations with ambient gas) leads to ohmic heating. So the temperature can be maintain. ICP

ICP: 

ICP

A typical inductively coupled plasma source called a torch : 

A typical inductively coupled plasma source called a torch

ICP Sample Introduction: 

ICP Sample Introduction Electro thermal Evaporation

Cross-Flow Nebulization: 

Cross-Flow Nebulization

Slide 26: 

1-3 cm above core: transparent and background free of Ar lines Core: non-transparent and white continuum output and spectrum of Ar Analyte atomization & ionization: Plasma appearance and spectra:

ICP: 

ICP Advantages • Plasma breaks virtually all bonds • Reduced interference (vs. FAAS or Arc/Spark AES) • Qualitative and quantitative measurement Disadvantages • Expensive to operate (Argon consumption) • Destructive and no information about oxidation states • Volatile organic solvents may extinguish plasma • Overlapping emissions lead to an increase of LOD to higher concentrations

Direct Current Plasma (DCP): 

Direct Current Plasma (DCP) 3 graphite anode in an inverted Y. Tungsten cathode at the inverted base. Plasma jet is formed by bringing the cathode into contact with anode. Sample aspiration is done at the area between the two arms of Y. Atomization and excitation is occur at plasma region. Use for organic solutions and aqueous solutions with a high solid content better than ICP.

Direct current plasma (DCP): 

Direct current plasma (DCP)

Slide 30: 

Advantages • Modest cost, linear response with time and concentration • Lower consumption of Ar (g) Disadvantages • Samples have fewer spectral lines vs. ICP, and less sensitive • Small, low intensity plasma • Requires large power supply • Graphite electrodes need to be replaced every few hours

Basic instrumentation in PES:: 

Basic instrumentation in PES:

PES instrument types: 

PES instrument types Three instrument types: 1)sequential (scanning and slew-scanning) 2)Multichannel - Measure intensities of a large number of elements (50-60) simultaneously 3)Fourier transform FT-AES

Slew scan spectrometer: 

Slew scan spectrometer Two slew-scan gratings Two PMTs for VIS and UV Most use holographic grating Rotation of grating by motor. Quick scanning

Applications of AES: 

1.Qualitative analysis : The presence of element is determine qualitatively by observing emission at the wavelength characteristic of the element. e.g. Emission at 766.5 nm indicates that potassium is present in a sample, while the bright yellow emission of sodium at 598 nm indicates its presence. 2. Quantitative Analysis : Flame OES can be used to determine the concentrations of elements in samples. The concentration of the element in the sample is calculated from comparison with an external calibration curve or by the standard addition method. Applications of AES

Slide 35: 

The calibration curve was constructed by aspirating Li standard solutions of 5 and 10 ppm Li and the blank solution (0.0 ppm Li). Each intensity was measured and a plot of intensity vs. concentration and from this we can calculate the concentrations of unknowns. In that an emission signal was detected in the standard that contained no lithium (the zero concentration standard or calibration blank). This is called the background signal or blank emission signal. In this case, the background emission was not subtracted from each standard, but was plotted as the 0.0 ppm Li standard. To use this curve, an unknown sample is aspirated, its emission intensity is measured and the concentration read (or calculated by the computer) from the calibration curve.

3. Specific applications. : 

3. Specific applications. Metals and alloys: Oils Animals and men Plant and soil The technique is used for clinical chemistry, biochemistry, environmental chemistry, geology, specialty and bulk chemical production, materials characterization of metal alloys, glasses, ceramics, polymers and composite materials, atmospheric science, forensic science, conservation and restoration of artworks by museums, agricultural science, food and nutrition science, industrial hygiene, and many other areas. The versatility of plasma emission spectrometry comes from its ability to determine a large number of elements rapidly in a wide variety of sample matrices.

Slide 37: 

The analysis of soil, water, and air for industrial pollutants is a common application. Contaminated soil and water can be analyzed as well as soil and water that have been treated to remove heavy metals. Biological and clinical chemistry applications of plasma emission spectrometry include determinations of those metals required for proper functioning of living systems, such as Fe, Cu, K, Na, P, S, and Se, in urine, blood, serum, bone, muscle, and brain tissue.

References:: 

References: 1) Instrumental methods of chemical analysis by Gurdeep R. Chatwal & Sham K. Anand , published by Himalaya publishing house Pvt.ltd, 2008-fifth edition. 2) Instrumental analysis by Doughs A. Skoog , F. James Holler , Stanley R. Crouch , Published by Cengage Learning India Pvt.ltd, 2008-first edition reprint. 3) Instrumental methods of analysis by Hobart H. Willard, Lynne L. Merritt, John A. Dean, Frank A. Settle, published by CBS publishers & distributors, seventh edition. 4) Vogel’s textbook of Quantitative chemical analysis by J Mendham, R C Denny, J D Barnes, M J K Thomas, published by Dorling Kindersley pvt.ltd, sixth edition. 5)Undergraduate instrumental analysis by James W. Robinson, Eileen M. Skelly Frame, George M. Frame ll, sixth edition.

Slide 39: 

Thank you for your attention …