intro n theory aas

8/13/2019 Intro n Theory AAS

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ABSTRACT

Atomic Absorption Spectroscopy (AAS) instrument is used to measures the absorption of light at

specific wavelengths by elements in the Free State, such as calcium. The objective of this

eperiment is to detect calcium in the supplement tablets. Then, this eperiment was conducted

to compare the concentration of un!nown sample (commercial calcium supplement) with the

amount of calcium that needed by human. "n!nown sample was prepared and the data obtained

was used to construct calibration curve. The concentration values that were obtained from

calibration curve are #$%.&#, ##'.'%, .'%, $*.& and #+.% ppm which respect to the p- ', ,

, %, and +. This showed that the larger the p- level, the less acidic a substance is. Since the

relationship between the p- level and the concentration of the un!nown solution was

determined, the effectiveness of the p- solubility and the digestion system in the human.

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INTRODUCTION

The eperiment was conduct to determine the calcium content present in commercial

tablets using Atomic Absorption Spectroscopy (AAS). alcium is an essential mineral found in

great abundance in the body and also essential for living organisms mostly in cell physiology. As

a major material used in minerali/ation of bones and shells, calcium is the most abundant metal

by mass in many animals and in humans. 0inety1 nine percent (##2) of all the calcium in the

body is found in the bones and teeth. The remaining one percent ('2) is in the blood. alcium

plays important roles in nerve conduction, muscle contraction, and blood clotting. 3tracellular

calcium is also important for maintaining the potential difference across ecitable cell

membranes, as well as proper bone formation. 4f calcium levels in the blood drop below normal

levels, calcium is transferred from the bones to the blood in order to maintain blood calcium

levels. Therefore, it is important to consume sufficient calcium to maintain ade5uate blood and

bone calcium levels.

alcium supplements are used to prevent and to treat calcium deficiencies. 6ost eperts

recommend that supplements be ta!en with food and that no more than * mg should be ta!en

at a time because the percent of calcium absorbed decreases as the amount of calcium in the

supplement increases. 4t is recommended to increase doses throughout the day. 4n addition, they

also recommended that daily calcium inta!e for adults7 ranges from ' to '+ mg and

suggested to ta!e supplements with food to support in absorption.

Atomic spectroscopy is the determination of elemental composition by its

electromagnetic or mass spectrum. The study of the electromagnetic spectrum of elements is

called 8ptical Atomic Spectroscopy. 3lectrons eist in energy levels within an atom. These

levels have well defined energies and electrons moving between them must absorb or emit

energy e5ual to the difference between them. 4n optical spectroscopy, the energy absorbed to

move an electron to a more energetic level and9or the energy emitted as the electron moves to aless energetic energy level is in the form of a photon. The wavelength of the emitted radiant

energy is directly related to the electronic transition which has occurred. Since every element has

a uni5ue electronic structure, the wavelength of light emitted is a uni5ue property of each

individual element. As the orbital configuration of a large atom may be comple, there are many

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electronic transitions which can occur, each transition resulting in the emission of a characteristic

wavelength of light as illustrated in Figure '.

Figure ': The transition resulting in the emission of a characteristic wavelength of light.

The science of atomic spectroscopy has yielded three techni5ues for analytical use:

'. Atomic Absorption.

. Atomic 3mission.

. Atomic Fluorescence.

The process of ecitation and decay to the ground state is involved in all three fields of

atomic spectroscopy. 3ither the energy absorbed in the ecitation process, or the energy emitted

in the decay process is measured and used for analytical purposes.

Atomic Absorption Spectrophotometer (AAS) is designed to determine the amount

(concentration) of an object element in a sample, utili/ing the phenomenon that the atoms in the

ground state absorb the light of characteristic wavelength passing through an atomic vapor layer

of the element. 4n addition, it also provides accurate 5uantitative analyses for metals in water,

sediments, soils or roc!s. Atomic absorption units have four basic parts which are

interchangeable lamps that emit light with element1specific wavelengths, a sample aspirator, a

flame or furnace apparatus for volatili/ing the sample, and a photon detector.

AAS has been used to study structure1function relationships in foods for both li5uid and

solid to improve overall food 5uality, safety and sensory characteristics. Furthermore, it has also

used to investigate fungal infections in plant materials li!e fruits and seeds or to study mobility

of different chemical components in food materials. ;esides that, there are many applications of

AAS in the industries such as in chemical, petrochemical and refineries industries,

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pharmaceutical industries, recycling and waste management, water analytics and water treatment

and many more. 4n petrochemical and refineries industries, they apply AAS for determination of

heavy metals, sulfur, nitrogen, and chlorine in oil, fuel, paraffin, fatty acids and polymers. 4n

addition, they utili/e the AAS in identification of substance, 5uality control and sewages

analysis. 4n pharmaceutical industries, AAS are use in screening of human body and for active

ingredients. Additionally, they also apply for control of cleaning validation procedures and

identification of substances.

OBJECTIVE

'. To determine the commercial calcium supplement by Atomic Absorption

Spectrophotometry.

. To compare the concentration of un!nown sample (commercial calcium supplement)

with the amount of calcium that needed by human.

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THEORY

Atomic absorption units have four basic parts which are interchangeable lamps that emit

light with element1specific wavelengths, a sample aspirator, a flame or furnace apparatus for

volatili/ing the sample, and a photon detector. The techni5ue atomic absorption spectroscopy

typically ma!es use of a flame to atomi/e the sample, but other atomi/ers such as a graphite

furnace are also used. Three steps are involved in turning a li5uid sample into an atomic gas:

'. <esolvation = the li5uid solvent is evaporated, and the dry sample remains.

. >aporisation = the solid sample vaporises to a gas.

. Atomi/ation = the compounds ma!ing up the sample are bro!en into free atoms.

4f light of just the right wavelength impinges on a free, ground state atom, the atom may absorb

the light as it enters an ecited state in a process !nown as atomic absorption. This process is

illustrated in the Figure . Atomic absorption ta!es place when unecited atoms absorb energy

and become ecited atoms. 3lectrons can eist in one of two states:

'. ?round State: 4n this state, the electron contains the least energy possible, orbiting as close as

it can to the nucleus.

. 3cited State: 4n this state, the electron contains more energy than in its ground state,

orbiting further from the nucleus of the atom.

Absorption therefore is carried out by unecited atoms, whereas emission arises from ecited

atoms.

Figure : The atomic absorption process

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Atomic absorption measures the amount of light at the resonant wavelength which is

absorbed as it passes through a cloud of atoms. As the number of atoms in the light path

increases, the amount of light absorbed increases in a predictable way. ;y measuring the amount

of light absorbed, a 5uantitative determination of the amount of analyst element present can be

made. The use of special light sources and careful selection of wavelength allow the specific

5uantitative determination of individual elements in the presence of others. The atom obscure

re5uired for atomic absorption measurements is produced by supplying enough thermal energy to

the sample to dissociate the chemical compounds into free atoms. Aspirating a solution of the

sample into a flame aligned in the light beam serves this purpose. "nder the proper flame

conditions, most of the atoms will remain in the ground state form and are capable of absorbing

light at the analytical wavelength from a source lamp. The ease and speed at which precise and

accurate determinations can be made with this techni5ue have made atomic absorption one of the

most popular methods for the determination of metals.

The use of light absorption measurements to determine concentrations of atoms is called

atomic absorption spectroscopy (AAS). Although this phenomenon has been studied since early

in the nineteenth century, it was about '#* when the techni5ue became part of the analytical

repertoire, in large part as a conse5uence of wor! by @alsh in Australia. ;ecause of the

simplicity of the electronic structure of an atom (compared with a molecule), and the absence of

vibration and rotational transitions, atomic spectra are simpler than molecular spectra. 4nstead of

the band spectra characteristic of molecular absorption in the "> and visible regions, atoms

ehibit line spectra that is, the absorption pea!s are so narrow that they are essentially lines.

Some subtle effects are responsible for producing lines of finite width, but they are etremely

narrow nevertheless, with line widths of .'1.'A being typical. As a conse5uence, AAS is

capable of high specificity, since the narrow lines minimi/e the overlapping absorption so

common in molecular band spectra. As in any form of absorption spectroscopy, the light source

must generate radiation that includes the fre5uency that is absorbed by the sample. 4n AAS,etreme specificity is achieved by using as the light source a lamp whose emitting element is

identical with the element to be determined. The most common AAS flame gas miture is air1

acetylene, which generates a flame temperature of B.

Instrumentation of Atomic absorption spectroscop

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Figure : Schematic of an atomic1absorption eperiment

The e5uipment used in AAS is basically the same as for other spectroscopic absorption

methods. 4t consists of:

•

Ra!iation source

The light source is usually a hollow1cathode lamp of the element that is being measured.

Casers are also used in research instruments. Since lasers are intense enough to ecite atoms to

higher energy levels, they allow atomic absorption and atomic fluorescence measurements in a

single instrument. The disadvantage of these narrow1band light sources is that only one element

is measurable at a time.

• "onoc#romator

The function of the monochromator is to select radiation of the correct wavelength and

eliminate other radiation from the light path. For many elements such as sodium, potassium, and

copper the spectrum is simple and only low resolution monochromator is re5uired. -owever, for

certain other elements, particularly the transition elements, high resolution is necessary to

prevent unabsorbable emission lines.

• Detectors

Dhotomultipliers are used eclusively on commercial e5uipment. 4n practice, it is the

function of the detector to measure the intensity of radiation before and after absorption by the

sample. From this one can calculate how much radiation has been absorbed from the intense

beam.

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• Optica$ s$it sstem

Two slits are included in the optical system, an entrance slit and an eit slit. The entrance

slit serves to obtain a narrow, parallel beam of light from the source. The eit slit is used to select

radiation of the correct wavelength after it emerges from the monochromator.

• Atomi%er

The function of the atomi/er is to convert the combined atoms of the li5uid sample into

free atoms. The most common atomi/er is the flame. 4n practice the li5uid sample is introduced

into the flame in the form of a droplet. The droplets evaporate and leave a solid residue. The

residue, which contains the same atoms, is decomposed by the flame and free atoms are

liberated. These free atoms absorb the radiation which is measured in this procedure.

• Ana$tica$ &ariab$es

The 5uantitative application of atomic absorption spectroscopy is based on two

relationships. First, the degree of absorption is a function of how many free atoms are present in

the light path. Second, the number of free atoms is a function of the concentration of the metal on

the original sample. The process of atomi/ation depends on several variables. This are1

a) ;urner design

b) Sample flow rate

c) Type of flame

d) Solvent

e) @avelength choice

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'ROCEDURES

A stoc! solution with +ppm concentration is prepared using 'mC volumetric flas!.

Then a series of standard solution of +, '.+ and *.+ppm is to be prepared using the stoc!

solution f +ppm. The solutions then are to be used in calibration of the spectrometer. Five

different sample of p- is to be ta!en to be measured using Atomic Adsorption Spectrometer

(AAS). -aving the value of the standard solution, then the calibrating curve is plotted to

determine the concentration of the sample.

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RESU(TS AND CA(CU(ATION

i) Standard Solutions

Sample 0ame Sample oncentration (ppm) Adsorption

' . .

*.+ .#*

'.+ .%'

% +. .+*#

+ + .#%

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ii) Sample Solutions

Sample 0ame Sample oncentration (ppm) Adsorption

p- ' #$%.&# '.%%

p- ##'.'% '.%#

p- .*% .* p- % $*.& .'%

p- + #+.% .'++

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DISCUSSION

From the data obtained, the concentrations of calcium in the un!nown solution were calculated

via calibration curve. The calibration curve plays an important role as the reference to determine

the un!nown solutions. The calibration curve was measured using the standard solution which

had been prepared. The data was then accumulated in present of graph in term of the absorbance

versus the concentration. From the graph obtained, the e5uation of y E .'% .'& is used

to determine the concentration of the un!nown solutions. The un!nown solution of p- ' to p- +

is to be determined. From the graph plotted, the correlation coefficient value is .##$.

For the second graph the value of the concentration is calculated using the first e5uation obtain

from the calibration graph y E .'% .'&. The concentration for p- ' was #$%.&#ppm

with an adsorption of '.%%. Thus the second p- of p- was accumulated to have a

concentration of ##'.'%ppm. 4t adsorption value for p- was '.%#. The concentration of p-

was .*%ppm. The adsorption for the p- was .*. The concentration of p- % was

$*.&ppm. The adsorption for the p- % was .'%. The concentration of p- + was $*.&ppm.

The adsorption for the p- % was .'%ppm. The adsorption for the p- + was .'++.

<ue to the mista!e in calculating the mass need to be measured to prepared the stoc! solution

and the series of standard solution, the calibrating is giving a very slightly value for the edge.

The edge with decimal point (.') giving the concentration to be highly concentrated.

Although the value was in range .'+ to '.%, the highest concentration was turn to almost

'ppm. This is the error related to the second graph measurement for AAS. 3ven the

calibration is slightly wrong, the pattern of the concentration for the second graph is still can be

manually calculated as the value of the adsorption doesn7t correspondent to the calibration value.

As shown on the second graph, the highest concentration stated was in p- . This indicated that

the more acidic the solution, the higher concentration of the calcium. This pattern related that the

acidic solution have the more calcium to dissolved.

There are relationship between the p- and the concentration of the calcium hydroide. The same

scenario happens in the human stomach. The digestion process been divided into some part. The

acidic part was when the gastric acid is release from cells lining the stomach, which are coupled

to systems to increase acid production when needed. ?astric acid is a digestive fluid, formed in

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the stomach. 4t has a p- of ' to and is composed of hydrochloric acid (-l) (around .+2, or

+ parts per million), and large 5uantities of potassium chloride (Gl) and sodium chloride

(0al). The acid plays a !ey role in digestion of proteins, by activating digestive en/ymes, and

ma!ing ingested proteins unravel so that digestive en/ymes can brea! down the long chains of

amino acids. The acidic p- gain from the gastric acid have the possibility to dissolve the calcium

and other nutritious that the body needed. The same ways goes for the eperiment where the

calcium hydroide is strongly reacted with the lower p-. This indicated that at the lower p-, the

calcium hydroide can dissolved very well comparing to the higher value of p- or the basic

solution.

CONC(USION

4n the nutshell, the analytical techni5ue which Atomic Adsorption Spectroscopy (AAS) was used

was to determine the concentration of the calcium inside the un!nown solution. The relation of

the p- and the concentration was then investigated and to be determine to which p- has the

highest concentration. The relation between the concentration and the p- can be determining

from the calibration curve. As from the calibration curve, the e5uation of y E .'% .'&

was obtained. Thus, from the calculation of the concentration of the calcium content was related

to each of the p- investigated. . The concentration values which correspond to p- ', , , %, +

and * are #$%.&#, ##'.'%, .*%, $*.&, and #+.%ppm respectively. This had proven the

eistence of the relationship between the p- and the concentration of the calcium. . 6aimum

amount of calcium that recommended is *mg9C per day. 4n our stomach, gastric juice appears

at p- ' to p- in order to digest our food. The concentration of un!nown sample from p- ' to

p- is suitable for human body. The total concentration from p- ' to p- can be supported by

stomach. ;esides, this showed the concentration for p- in the range of ' to is ade5uate by

blood and bone calcium levels.

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http://en.wikipedia.org/wiki/Stomach

http://en.wikipedia.org/wiki/PH

http://en.wikipedia.org/wiki/Hydrochloric_acid

http://en.wikipedia.org/wiki/Parts_per_million

http://en.wikipedia.org/wiki/Potassium_chloride

http://en.wikipedia.org/wiki/Sodium_chloride

http://en.wikipedia.org/wiki/Proteins

http://en.wikipedia.org/wiki/Digestive_enzymes

http://en.wikipedia.org/wiki/Amino_acids

http://en.wikipedia.org/wiki/Stomach

http://en.wikipedia.org/wiki/PH

http://en.wikipedia.org/wiki/Hydrochloric_acid

http://en.wikipedia.org/wiki/Parts_per_million

http://en.wikipedia.org/wiki/Potassium_chloride

http://en.wikipedia.org/wiki/Sodium_chloride

http://en.wikipedia.org/wiki/Proteins

http://en.wikipedia.org/wiki/Digestive_enzymes

http://en.wikipedia.org/wiki/Amino_acids



RECO""ENDATION

'. 6a!e sure the sample preparation which is the dilution is conducted by a proper

procedure.

. "se digital pipette to ensure the eperiment easy to run and more accurate.

. 4t is better to have the e5uipment chec!ed and maintenance to prevent any error.

%. "se the eact cathode lamp to determine the correct composition.

+. Hinse and dried the apparatus to get a better calibration curve.

RE)ERENCES

http:99dietary1supplements.info.nih.gov9factsheets9calcium.asp

http:99www.calciuminfo.com9about9foodsources.asp

S!oog, <. A., -oller, F. I., J 0ieman, T. A. ('##$). Principles of Instrumental Analysis. ;roo!s

ole.

S!oog, <. A., @est, <. 6., -oller, F. I., J rouch, S. H. (%). Fundamentals of Analytical

Chemistry. ;roo!s ole.

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intro n theory aas

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