Embed Size (px)
Citation preview
Atomic Absorption Spectrometer (AAS) PerkinElmer Aanalyst 100
January 5th -6th, 2015
Instrument Center
Science and Technology Faculty Prince of Songkla University
Pattani Campus
Contents
Schedule
Trainee List
Part 1 Introduction and Application of AAS
Part 2 Using and Maintenance of AAS
(Perkins Elmer Aanalyst 100)
Schedule of “Using Atomic Absorption Spectrometer (AAS) Perkins Elmer Aanalyst 100” Training
January 5th -6th, 2015 At Instrument Center, 3th floor, Building 25
Faculty of Science and Technology, Prince of Songkla University *******************************
January 5th, 2015 08.15 - 08.30 am Registration 08.30 - 08.45 am Inauguration 08.45 – 10.15 am Introduction of AAS Assoc.Prof.Dr. Boonsong Krisornpornsan 10.15 – 10.30 am Coffee Break 10.30 – 12.00 am Application of AAS Assoc.Prof.Dr. Boonsong Krisornpornsan 12.00 – 01.00 pm Launch 01.00 – 02.30 pm Using and Maintenance of AAS (Perkins Elmer Aanalyst 100) Mr.Pisipong Meunprasertdee 02.30 – 02.45 pm Coffee Break 02.45 – 03.00 pm Workshop 2 groups 03.00 – 04.30 pm Workshop #1 Preparation of standard and sample for using AAS (Perkins Elmer Aanalyst 100) January 6th, 2015 08.45 – 10.15 am Workshop # 2 Using AAS (Perkins Elmer Aanalyst 100) 10.15 – 10.30 am Coffee break 10.30 – 12.00 am Workshop # 2 Using AAS (Perkins Elmer Aanalyst 100) 12.00 am – 01.00 pm Launch 01.00 – 03.30 pm Workshop # 3 Maintenance Perkins Elmer Aanalyst 100 03.30 – 03.45 pm Coffee break 03.45 – 04.35 pm Test AAS principle and using
***********************************
Training of “Using Atomic Absorption Spectrometer (AAS) Perkins Elmer Aanalyst 100” Training
January 5th -6th, 2015 At Instrument Center, 3th floor, Building 25
Faculty of Science and Technology, Prince of Songkla University
*******************************
No Name - Surname Year/Degree/Major Code Signature 1 Dr. Areefen Rassamesard Lecturer, Physics 1
2 Miss Nussaba Boonyasak 4th year, Bachelor's degree, Food Science and Nutrition
2
3 Miss Pawwida Wongna 4th year, Bachelor's degree, Food Science and Nutrition
1
4 Mr. Bashir Algaily 2nd year, Master's degree, Applied Physics 2
5 Mr. Atthapon Saman 5th year, Bachelor's degree, Agricultural Technology
1
6 Ms. Trinh Ngoc Thao Ngan 2st year, Master's degree, Food Science and Nutrition
2
7 Dr.Sunaree Bordeepong Lecturer, Physics 1
8 Ms.Haleemoh Weasamaae 4th year, Bachelor's degree, Fishery Technology 2
9 Mr. Roslan Chemae 4th year, Bachelor's degree, Fishery Technology 1
10 Mr.Viroj Pinprom Graduate, Bachelor's degree, Chemistry and Biology
2
11 Mrs.Saijai Maneerat Graduate, Master's degree, Soil Management 1
Part 1 Introduction and Application of AAS
05/01/58
1
Atomic Absorption Spectrophotometry
(AAS)
By
Assist. Prof. Dr. Boonsong Krisornpornsan
ผศ. ดร. บญุสง ไกรศรพรสรร1
History of optics and light studies
His experimentl i t- lens, mirrors etc.
His study- Ray of light
Ibn Alhazen965-1039
(Father of optics) 2
05/01/58
2
Historical background of spectroscopy
The first to turn hi t l this telescope to the heavens.
- Moon, sun spots etc.
Galileo Galilei (1564-1642) 3
A quantitative study of light
The first people t t d li htto study light scientifically.
- Prism- Spectrum
Sir Isaac Newton (1643-1727) 4
05/01/58
3
Original studies of light
5
Newton’s contribution to spectroscopy
6
05/01/58
4
Classification of electromagnetic radiation
7
Advancements in the study of light
-Fraunhofer lines in the sun’s spectrumsun s spectrum - Developed a spactroscope- Dratings
Joseph von Fraunhofer (1787-1826)
German optician8
05/01/58
5
Color of light
-heat the element
Gustav Robert Kirchhoff(1824-1887)
German physicist
Robert Wilhelm Eberhard Bunsen
(1811-1899)German chemist
9
Emission spectra complement absorption spectra
10
05/01/58
6
Hydrogen line spectrum
11
Scanning spectrophotometer (side view)
12
05/01/58
7
Scanning spectrophotometer (top view)
13
Computer output from scanning spectrophotometer
14
05/01/58
8
Hydrogen spectrum – The Balmer series
Wavelength( )
color(nm)656.2 red486.1 blue434.0 blue-violet410 1 violet
Johann Jakob Balmer (1825-1898)
410.1 violet
15
Quantum properties of light
ΔE = nhν
ΔE – the change in Energyin Energy
n= 1, 2, 3, …
h – (Planck’s constant)
h = 6.626×10-34 Js
ν - frequency
Max Karl Ernst Ludwig Planck (1858-1947)
German physicist16
05/01/58
9
Quantum model for the Hydrogen atom
Neils Henrik David Bohr (1885-1962)
Danish physicist 17
Bohr’s Model
N lNucleus
Electron
Orbit
Energy Levels18
05/01/58
10
Excitation
+ energy
Mo M*+E
Excited electron
19
Decay and Emission
- EBack to ground state
light
Mo M* Mo+E -E
20
05/01/58
11
Origins of atomic spectra
li htexcited states
λ1
λ3
λ2
light
∆E = hƲ
21
Atomic Spectra
Every chemical element has own unit spectral fi i tfingerprint.
Emission spectrum ofEmission spectrum of hydrogen
Absorption spectrum of hydrogen 22
05/01/58
12
Electrons jump
Emission spectroscopy
j pfrom higher levels to lower ones.
Energy is released or emitted in the form of light of specific energy g p gy(or color).
Electrons must first be excited up to higher levels. This is done either with heat (eg. Flame tests) or light (atomic emission spectra).
23
Electrons jump
Absorption spectroscopy
Electrons jump from lower levels to higher ones.
Energy is absorbed in the form of light of specific energy (or p gy (color).
This is the method used in UV-Vis spectroscopy and atomic absorption spectroscopy (AAS) and many others.
24
05/01/58
13
A spectrum
Emission linesC ti
Absorption linesContinuum
p
A spectrum = the amount of light given off by an object at a range of wavelengths.
25
The colors come from the different energies, frequencies and wavelengths of light.q g g
They are properties of light and all interconnected.
26
05/01/58
14
Calculations for energy levels
)(10178.2 2
218
nZJE −×−=
When Z = atomic number of element
t bn = quantum number & the units are Joules
27
Calculations the Balmer & Lyman series
Rydberg equation
When Ʋ = frequencyn = quantum numberR R db t t
)11( 22
21 nn
R −=ν
R = Rydberg constant= 3.29 x 1015 Hz
1 Hz = 1 s-1
28
05/01/58
15
Frequency (ν) V.S Wavelength (λ)
λ = cλ ν = c
C = speed of light= 2.9979 X 108 m/s
29
Red light has the longest wavelength of visible light This
Violet light has the shortest wavelength of visible light and has
0 4
0.6
0.8
1.0
1.2
bsor
banc
e
light. This also means it has the lowest frequency and lowest energy.
light, and has the highest energy.
0.0
0.2
0.4
400 440 480 520 560 600 640 680 720 760
Wavelengths (nm)
Ab
The maximum absorption occurs 30
05/01/58
16
How are color and light absorption are related?
31
Just as light can be split into its various colors, so these colors can be recombined to form white light.
Mixing all these colored lights would give us white, but we can also use combinations of fewer colors tobut we can also use combinations of fewer colors to get white.
32
05/01/58
17
We can see that red, blue and green light add together to make white light. But where green overlaps magenta, white light is also formed. Same with red and cyan. And with yellow and blue.
We call these colors ‘complementary’
33
Complementary colors are on the opposite sides of the color wheel.
They help us understand the colors we see when light is absorbed. 34
05/01/58
18
If we take blue light away from white light (absorb blue), what color remains?
35
The absorption spectra of individual atoms have very distinct lines showing which energies of light have been absorbed as the electrons jump to higher levels.
36
05/01/58
19
The absorption spectra of compounds tends to have broad overlapping regions for all the possible electron jumps.
37
This is the type of absorption spectra which is obtained using a using a UV-Vis spectrophotometer.
The position of the peak shows the wavelength of the light most strongly absorbed and what % is absorbed.38
05/01/58
20
This substance is absorbing the red/orange light (~600 nm) and transmitting the rest which our eye mixes and interprets as blue/green.
39
White light shining on a white object.
All light is reflected.40
05/01/58
21
White light shining on a red object.
Red light is reflected- other colors absorbed (particularly green and similar colors).
41
This is a more realistic view of this. The reflected colors combine and are mixed in the brain to give the overall red color.
42
05/01/58
22
White light shining on a blue object.
43
44
05/01/58
23
White light shining on a black object.
All light is absorbed. Black is the absence of light.
White light shining on a grey object. A small amount of each color is reflected.
45
Atomic Spectroscopy
EmissionEmissionMo + heat M* Mo + light
AbsorptionMo + light M*
46
05/01/58
24
Atomic Spectroscopy (AS)
1. Atomic Absorption Spectroscopy (AAS)
2. Flame Atomic Emission Spectroscopy (FAES)
3. Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP)
47
Basic principle
AAS is an analytical technique that measures the concentrations of elements. It makes use of the absorption of light by these elements in order to measure their concentration.
-จาํนวนหรอืปรมิาณของ unexcited atoms ที่จะ absorb แสง ซึง่ emit มาจาก excited atoms ของ element ชนดิเดยีวกนั
48
05/01/58
25
- AAS quantifies the absorption of ground state atoms in the gaseous state.- The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. The analyte concentration is determined from the amount of absorption. - Concentration measurements are usually determined from a working curve after calibrating the instrument with standards of known concentrationconcentration.- Atomic absorption is a very common technique for detecting metals and metalloids in a samples.
49
detectable
50
05/01/58
26
AAS
AAS have 4 principal componentsp p p
1. A light source (Continuum and line source) (usually a Hallow Cathode Lamp (HCL))
2. An atom cell (atomizer)
3. A monochromator
4. A detector, and read out device51
Schematic Diagram of an AAS
Light source Atomizer Monochromator Detector and readout device
52
05/01/58
27
53
HCL
HCL contains a tungsten anode and a
Quartz window
hollow cylindrical cathode made of the element to be determined. These are sealed in a glass tube filled with an inert gas
Pyrex body
filled with an inert gas (Ne or Ar).
54
05/01/58
28
How HCL works?Applying a potential difference between the anode and the
cathode leads to the ionzation of some gas atoms (Ne/Ar).These gaseous ions bombard the cathode and eject metal atoms
from the cathode in a process called sputtering. Some sputtered atoms are in excited states and emit radiation characteristic of theatoms are in excited states and emit radiation characteristic of the metal as they fall back to the ground state.
The shape of the cathode which is hollow cylindrical concentrates the emitted radiation into a beam which passes through a quartz window all the way to the vaporized sample.
Since atoms of different elements absorb characteristic wavelengths of light. Analyzing a sample to see if contains a particular element means using light that element. 55
HCL emission process
1. Ionization 2. Sputtering
+-
+
+ +
-
3. Excitation 4. Emission
Neo Ne+ Ne+
Mo
M* M*+ +- -Mo Mo
M M
Ne+ light
56
05/01/58
29
For example with sodium,A lamp containing sodium emits light from excited sodium atoms that produce the light mix of wavelengths to be absorbed by any sodium atoms from the sample.
A beam of the electromagnetic radiation emitted from excited sodium atoms is passed through the vaporized sample. Some of the radiation is absorbed by the sodium atoms inradiation is absorbed by the sodium atoms in the sample. The greater the number of atoms there is in the vapor, the more radiation is absorbed.
57
Considerations
1. Type of HCL
2. Position of HCL
3. Current adjust of HCL
58
05/01/58
30
Atomizer
Elements to be analyzed needs to be in atomic sate.
Atomization is separation of particles into individual molecules and breaking molecules into atoms. This is done by exposing the analyze to high temperatures in a flame or graphite furnacegraphite furnace.
59
The role of the atom cell is to primarily dissolved a liquid sample and then the solid particles are vaporized into their free gaseous ground state form. In this form atoms will be available to absorb radiation emitted from the light source and thus generate a measurable signal proportional to concentration.
There are two types of atomization: Flame and Graphite furnace atomization.
60
05/01/58
31
61
Flame
Flame AA can only analyze solutions, Where it uses a slot type burner to increase the path l th d th f t i th t t llength, and therefore to increase the total absorbance
Sample solutions are usually introduced into a nebulizer the sample is dispersed into tiny droplets which can be readily broken down indroplets, which can be readily broken down in the flame.
62
05/01/58
32
Flame Atomizers
1. Used in all atomic spectroscopic techniquesp p q
2. Converts analyze into free atoms in the form of vapor phase free atoms
3. Heat is required
4. Routes for sample introduction
63
Various flame atomization techniques 64
05/01/58
33
Types of flames used in Atomic spectroscopy
Fuel and Oxidant Temperature, oCGas/air 1700-1900Gas/O2 2700-2800H2/air 2000-2100H2/O2 2550-2700Acetylene/air 2100-2400Acetylene/air 2100 2400Acetylene/O2 3050-3150Acetylene/N2O 2600-2800
65
Processes that take place in flame
Solution of analyze
Nebulization
Spray
Solid/gas aerosol
Gaseous molecules
Desolvation
Volatilization Excited molecules
hƲ molecular
molecules
Atoms
Atomic ions
Dissociation
Ionization
Excited atoms
Excited ions
hƲ atomic
hƲ ionic
66
05/01/58
34
Effect of flame temperature on excited state population
E*, g* = 3 Excited state
n
Eo, go = 2 ground state
∆E
Emis
sion
Abso
rptio
n
Atoms in excited stateEnergy difference
N* = g*e-∆E/kT
No goAtoms in ground state
Statistical factor
Boltzmann constant (1.381x10-23)
Temperature (K)
67
The lowest excited state of a sodium atom lies 3.371X10-19 J/atom above the ground state. The degeneracy of the excited state is 2, while that of the ground state is 1 Let’s calculate thethat of the ground state is 1. Let s calculate the fraction of sodium atoms in the excited state in an acetylene-air flame at 600 K.
N* = g*e-∆E/kT
No go
N* = 2e-3.371x10-19/(1.381x10-23*2600)
No 1= 1.67x10-4
That is, less than 0.02 % of the atoms are in the excited state.68
05/01/58
35
Thus 99 996 % of Na atoms are in the ground stateThus 99.996 % of Na atoms are in the ground state.
Atomic emission uses excited atoms.
Atomic absorption uses ground state atoms.
69
How would the fraction of atoms in the excited state change if the temperature were 2 610 K instead?
N* = 2e-3.371x10-19/(1.381x10-23*2610)
No 1= 1.74x10-4
The fraction of atoms in the excited state is still less than 0.02 %, but that fraction has changed by 100*(1.74-1.67)/1.67 = 4 %
70
05/01/58
36
Ratio of excited- to ground-state atoms for lines with varying excitation energies at increasing temperature
element Line (nm)
g*/go E (J) Ratio of excited- to ground-state atoms2000 K 4000 K 6000 K 8000 K
Cs 852.1 2 2.34x10-19 4.19x10-4 2.90x10-2 1.19x10-1 2.41x10-1
Na 589.1 2 3.38x10-19 9.65x10-8 4.39x10-3 3.38x10-2 9.37x10-2
Ca 422.7 3 4.66x10-19 1.40x10-7 6.47x10-4 1.08x10-2 4.41x10-2
Zn 213.9 3 9.13x10-18 1.30x10-14 1.98x10-7 4.90x10-5 7.70x10-4
71
Atomization devices
Atomization:1. A process of forming free atoms by heat2 At i d i th t t t i ti2. Atomizers are devices that carry out atomization:
2.1 Continuous (constant temperature with time)-Flame-Plasma
2.2 Non-continuous (temperature varies with time)-Electrothermal-Spark discharge
72
05/01/58
37
Sample introduction systems
In continuous atomizers sample is constantly introduced in form of droplets, dry aerosol, vapor.
Nebulizer: A device for converting the solution into fine spray or droplets
Continuous sample introduction is used with continuous nebulizers in which a steady state atomic population is produced. Sample is introduced in fixed or discrete amounts.
73
Discontinuous samplers are used with continuous atomizers
1. Discrete samples are introduced into atomizers in many ways:
Electrothermal atomizers A syringe is used .A transient signal is produced as temperature changes with time and sample is consumed.
2 Indirect insertion (probe)2. Indirect insertion (probe)Sample is introduced into a probe (carbon rod) and
mechanically moved into the atomization region vapor cloud is transient because sample introduced is limited.
74
05/01/58
38
3. Flow injectionThe analyte is introduced into the carrier stream into a
nebulizer as mist
4. Hydride generationThe volatile sample is stripped from the analyte solutionThe volatile sample is stripped from the analyte solution
and carried out by a gas into the atomizer. This strip is followed by chemically converting the analyte to hydride vapor form.
5. With Arc sparkSolids are employed.
6. Laser microbe techniqueA beam of laser is directed onto a small solid sample, gets
vaporized, atomized by relative heating, Either sample is probed by encoding system or vapor produced is swept into a second absorption or fluorescence. 75
Nebulization gas is always compressed, usually acts as the oxidant, it is oxygen in flame and argon in plasma
Nebulization chambers produce smaller droplets p pand remove or drain larger droplets called aerosol modifiers.
Aspiration rate is proportional to compressed gas pressure. The pressure drops through capillary, here ¼ ill di t d d Thi i¼ capillary diameters are recommended. This is inversely proportional to viscosity of the solution.
Peristaltic and/or syringe pumps could be used.76
05/01/58
39
Oxidant and fuel are usually brought into nebulization chamber through a separate port. They mix and pass the burner head called premixed burner system.
Add organic solvents to reduce the size of the drop.
77
The atomic absorption spectrometer
Sample Introduction System
Nubulizer
Capillary
Solution78
05/01/58
40
The fine mist of droplets is mixed with fuel (acetylene), and oxidant (air or nitrous oxide) and burned.
The flame temperature is important because it influences the distribution of atoms. It can be manipulated by oxidant and fuel ratiomanipulated by oxidant and fuel ratio.
79
Monochromators
This is a very important part in an AAS. It is used to separate out all of the thousands of lines. Without a good monochromator, detection limits are severely compromised.
A monochomator is used to select the specific wavelength of light which is absorbed by the sample, and to exclude other wavelengths The selection ofand to exclude other wavelengths. The selection of the specific light allows the determination of the selected element in the presence of others.
80
05/01/58
41
Detector and read out device
The light selected by the monochromator is directed onto a detector that is typically a photomultiplier tube, whose function is to convert the light signal into an electrical signal proportional to the light intensity.
The processing of electrical signal is fulfilled by a signal amplifier. The signal could be displayed for readout or further fed into a data station for printoutreadout, or further fed into a data station for printout by the requested format.
81
Calibration curve
A calibration curve is used to determine the unknown concentration of an element in a solution. The instrument is calibrated using several solutions of known concentrations. The absorbance of each known solution is measured and then a calibration curve of concentration vs absorbance is plotted.
The sample solution is fed into the instrument andThe sample solution is fed into the instrument, and the absorbance of the element in this solution is measured. The unknown concentration of the element is then calculated from the calibration curve.
82
05/01/58
42
Absorbance V.S Concentration
83
Interferences
The concentration of the analyte element is considered to be proportional to the ground state
t l ti i th fl f t th t ff tatom population in the flame, any factor that affects the ground state atom population can be classified as an interference.
Factors that may affect the ability of the instrument to read this parameter can also be classified as anto read this parameter can also be classified as an interference.
84
05/01/58
43
The different interferences that are encountered in atomic absorption spectroscopy are:
1. Absorption of source radiation: Element other than the one of interest may absorb the wavelength being used.
2. Ionization interference: the formation of ions rather than atoms causes lower absorption of radiation. This problem is overcome by adding ionization suppressors.
3. Self absorption: the atoms of the same kind that are absorbing radiation will absorb more at the center of the line than at the wings, and thus resulting in the change of shape of the line as well as its intensity.
4. Background absorption of source radiation: This is caused by the presence of a particle from incomplete atomization. This problem is overcome by increasing the flame temperature.
5. Transport interference: rate of aspiration, nebulization, or transport of the sample (e.g viscosity, surface tension, vapor pressure, and density)85
Atomic emission spectroscopy
Atomic emission spectroscopy is also an analytical technique that is used to measure the concentrations of elements in samples.p
It uses quantitative measurement of the emission from excited atoms to determine analyte concentration.
The analyte atoms are promoted to a higher energy level by the sufficient energy that is provided by the high temperature of the atomization sources.
The excited atoms decay back to lower levels by emitting light . Emission are passed through monochromators or filters prior to detection by photomultiplier tube.
86
05/01/58
44
The instrumentation of atomic emission spectroscopy is the same as that of atomic absorption but without the presence of a radiation source.
In atomic emission the sample is atomized and the analyte atoms are excited to higher energy levels all in the atomizer.
87
Schematic diagram of an atomic emission spectrometer
88
05/01/58
45
The source of energy in atomic emission could be a flame like the one used in atomic absorption, or an ICP.
1. The flame (1700-3150 oC) is most useful for elements with relatively low excitation energies like sodium, potassium and calcium.
2. The flame (6000-8000 oC) has a very high temperature and is useful for elements of hightemperature and is useful for elements of high excitation energies.
89
Comparison between atomic absorption and emission spectroscopy
absorption emission1. Measure trace metal concentrations in complex matrices.
1. Measure trace metal concentrations in complex matrices.
2. Atomic absorption depends upon the number of ground state atoms.
2. Atomic emission depends upon the number of excited state atoms.
3. It measures the radiation absorbed by the ground state atoms.
3. It measures the radiation emitted by the excited state atoms.
4. Presence of a light source (HCL). 4. Absence of the light source.5. The temperature in the atomizer is adjusted to atomize the analyteatoms in the ground state only.
5. The temperature in the atomizer is big enough to atomize the analyteatoms and excite them to a higher energy level.
90
05/01/58
46
AAS applications
They are many applications for atomic absorption:
1 Clinical analysis: Analyzing metals in biological fluids such as blood1. Clinical analysis: Analyzing metals in biological fluids such as blood and urine.
2. Environmental analysis: Monitoring our environment: e.g finding out the levels of various elements in rivers, seawater, drinking water, air, soil and petrol.
3. Pharmaceuticals
4. Industry
5. Mining
6. Food, Cosmetics, Hair, Plant, Animal etc.91
The use of AAS
1. The type and current of HCL2 The wavelength for analysis2. The wavelength for analysis3. The flame4. Chemical treatment5. Interferences
92
05/01/58
47
Detection limit (DL)
3X
noise3X
-Standardization by IUPAC-DL = Conc. Producing signal that is 3 times noise levelDL 3 td d f bl k-DL = 3x std dev of blank
-Defines signal to noise ratio-Provides information on:1. Total instrument performance2. Lower limit of concentration measurement 93
