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Laporan Uv Vis_ni Kadek Wahyuni Antari

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  • ANALYSIS OF COPPER CONTENT IN COPPER ORES AND ACTIVE COMPOUND IN SUNSCREEN LOTION TROUGH ULTRAVIOLET-VISIBLE SPECTROPHOTOMETER

    Ni Kadek Wahyuni Antari (1213031002)

    Chemistry Education Department, Faculty of Mathematics and Natural Sciences Universitas Pendidikan Ganesha

    INTRODUCTION

    Ultraviolet-visible spectroscopy is a method of analysis based on based on molecular

    absorption by using ultraviolet radiation and visible light. The ultraviolet radiation has wavelength between 160-400 nm and the visible light have wavelength between 400-800 nm. Ultraviolet-visible spectroscopy is one type of spectroscopy that provides a simple way to set a small quantity of a substance in solution form. The principle of this spectroscopy is based on the interaction of electromagnetic radiation energy to chemical substances [2]. This method is widely used in quantitative measurement of organic and inorganic compounds. If certain wavelengths of light absorbed by an atom or molecule, it will produce the spectrum of absorption. Electronic structures of molecule determine the absorption light of molecule.

    Spectroscopy of molecule absorbance is based on the measurement of transmittance T or absorbance A of a solution with concentration C in the transparence cell with length of b cm.

    Absorbance position is related with radiation wavelength ( ), whereas the energy is the same with energy needed for electronic transition, while transmittance or absorbance is depend on the two factors, ability of interaction between radiation energy and electronic system as well as difference between ground state and excited state. Quantitatively, it can be stated as the following Lambert-Beer equation:

    A = b c = - log T = - log0I

    I= log

    I

    I 0

    C b I

    Ilog-

    0

    whereas, A is absorbance , T is transmittance, I is light intensity emmited by solution in cell, I0 is light intensity emmited by solvent in cell on same I. is comparator constant (L cm-1 mol-1), b is length of solution passed by light (generally, 1 cm) and C is concentration of absorbent species in mol L-1 (M) unit.

    The examples of analysis by using UV-visible spectroscopy are analysis of the copper in ore copper and active compound in sunscreen lotion. Copper (II) sulphate pentahydrate (CuSO4.5H2O) is one of complex compound that has blue color. The blue color of CuSO4.5H2O is caused by the metal involved and the number of d orbital, associated with the oxidation state. The ions formed from Cu+ ions are generally colorless; while the ions formed from ion Cu2+ is generally blue. This happens because the configuration of Cu+ ions that has electron configuration [Ar] 4s03d10, it appears that its 3d sub shell fully charged. While the configuration of Cu2+ ions that has electron configuration [Ar] 4s03d9, 3d sub shell was not fully charged. This

  • makes it possible to absorb light energy, which caused the excitation so that, it can emit light energy that matches the color of light can be reflected when it returns to the ground state.

    Many modern technologies depend on the metal. Since it has become must for a chemist to analyze ore to determine the content and developing methods for the discovery of metal that has a commercial value. One of the important metals in technology and economic value is copper, widely used for conductors, water pipes, and a mixture of other metals known as alliances (such as brass, bronze and silver). Spectrophotometry is widely used in analytical laboratories. Most laboratories require identification and determination of organic compounds and inorganic (e.g. pharmaceuticals, fertilizers, mining etc.) by using a spectrophotometer [3]. In this experiment will be determined percentage of mass of copper in copper ore by using spectroscopic techniques. If w is the mass of copper ore was taken and 100 mL is the total volume of solution, so the percentage of copper in ore copper is as follows.

    0.10 63.55 100

    = %

    Besides, active compound in sunscreen lotion is also can be analysis by using UV-visible spectroscopy. The sun emits electromagnetic radiation to the earth with a range of 290 nm to 800 nm. The ultraviolet radiation has wavelength between 160-400 nm. So, the ultraviolet radiation is also emitted by the sun. There are two types of ultraviolet radiation, UV A and UV B. The range of UV A is approximately 320-400 nm and UV-B approximately 280-320 nm. Ultraviolet is very dangerous for skin. Therefore, skin must be protected with sunscreen lotion to avoid radiated directly on the skin of the tropical sun. UV-B is responsible for skin damage (sunburn and tanning). When skin is exposed to ultraviolet radiation, skin cells will produce a brown pigment called melanin and will become more brown skin and thinning. More and more subject to ultraviolet radiation in the range 290-320 nm the more melanin is formed and the skin will be darker. Furthermore, ultraviolet radiation causes skin damage to DNA and proteins, thus causing a very dangerous effect are skin cancer or melanoma [3].

    Sunscreen lotion is a product containing a compound that can absorb, scatter or reflect sunlight on the skin, so it can be used to protect the function and structure of human skin from damage caused by sunlight. Kaemferia galanga L. is one of the many traditional medicinal plants contain natural ingredients compounds, one of them is ethyl p-methoxycinnamate is the main content of Kaemferia galangal L. Ethyl p-methoxycinnamate (EPMS) is one of the compounds that are the basic ingredients of sunscreen lotion that protects skin from UV radiation. EPMS included in the class of ester compounds containing benzene ring and the non-polar methoxy group and the carbonyl group which binds less polar ethyl [4].

    O

    OC 2H 5

    H 3CO

    Picture 1. The structure of EPMS

  • The objectives of this experiment were 1) to make standard curve and analysis of copper content in a copper ore and 2) to analyze active compound contained in sunscreen lotion (Citra Body Lotion).

    METHODS

    1. Materials and Equipment

    This experiment was conducted by using several equipment and materials. Equipment used in this experiment were beaker 100 mL (6 pieces), watch glass (1 piece), spatula, stirrer rod, volumetric flask 100 mL (1 piece), volumetric flask 50 mL (1 piece), volumetric flask 25 mL (2 pieces), and volumetric flask 10 mL (2 pieces), graduated pipette 10 mL (1 piece), and drop pipette (1 piece). Then, materials used in this experiment were CuSO4 hydrate (1.2475 grams), aquades (as needed), copper ore (0.502 grams), concentrated H2SO4 (as needed), ethanol (as needed), and Citra Body Lotion (as needed). The instrument used was UV-Vis spectrophotometer.

    2. Procedure

    2.1 Analysis CuSO4.5H2O as Standard Solution

    A total of 1.2475 grams of CuSO4.5H2O were dissolved in 50 mL of aquades. Then, its solution was diluted until the concentration 0.02 M, 0.04 M, 0.06 M, and 0.08 M. Theirs solution were prepared as a standard. Then, the absorbance of standard solution was measured by using UV-visible spectrophotometer.

    2.2 Analysis Copper Content in Copper Ore

    A total of 0.502 grams of copper ore was weighed and placed in beaker 100 mL. Then, the copper ore was added by 2 mL of concentrated sulfuric acid drop by drop. The reaction was waited until it was stopped and then continued by adding more sulfuric acid until all copper were soluble. The mixture was heated slowly until it boils for 1-2 minutes for complete reaction. Solution was cooled and it was added by 10 ml of aquades. It was kept a few minutes until produce precipitate as the contaminant, and then it was separated by decantation. The filtrate entered into the volumetric flask 100 mL and it was added by aquades until reach the scale. The solution was shaken in order to get homogeneous solution. The absorbance of the solution was measured by using UV-Vis spectrophotometer.

    2.3 Analysis of Active Compound in Citra Body Lotion

    Small amount of Citra Body Lotion was diluted into ethanol in beaker. Then the absorbance was measured by UV-Vis spectrophotometer.

  • RESULTS AND DISCUSSION

    Analysis CuSO4.5H2O as Standard Solution

    In this experiment, it was made sample solution of CuSO4 0.1 M as much as 50 mL by weighing a total of 1.2475 gram of solid CuSO4.5H2O. The color of CuSO4.5H2O is bluish color because CuSO4.5H2O is a complex compound that has bluish color. Ions are formed in the solution in the form of Cu2+ ions that are generally blue. This occurs because of the configuration of Cu2+ ions (4s03d9), 3d orbitals are not fully charged. This allows it to absorb light energy, which is caused by the excitation of electrons that can emit light energy that matches the color of light that can be reflected when you return to the ground state. Cu2+ ions have 3d9 configuration, which is causing Cu2+ cation has coordination number 6. In water, CuSO4 solution is in the form of the complex [Cu(H2O)4]2+ can be written CuSO4.5H2O.

    Picture 2. The Structure of Complex Compound of CuSO4.5H2O

    In the case of copper (II) sulphate, 4 water molecules are covalently bonded to form effectively a square planar complex ion, [Cu(H2O)4]2+ and the 5th water molecule H2O is hydrogen bonded to this ion and hydrogen bonded to a neighbouring sulphate ion SO42- thus helping to hold the crystal lattice together, though the main force of attraction is the electrostatic attraction between copper complex ion and the sulphate ion. Therefore, the water of crystallization number doesn't equal the co-ordination number of the central metal ion.

    [Cu(H2O)4]2+, H2O, SO42- are the three components of the crystal structure of copper (II) sulfate pentahydrate, and all three are linked by hydrogen bonds. The full structure is a bit complicated to draw but the 5th and 6th octahedral positions of the Cu2+ ion are occupied by oxygen atoms of the sulfate ion and the 5th water molecule is held in position by hydrogen bonding. However, this blue crystal lattice is readily broken down on heating, a classical demonstration of a reversible reaction, since the white anhydrous solid turns blue on adding water.

    CuSO4.5H2O CuSO4 + H2O Furthermore, theories of crystal field can explain the color that is produced in complex

    compound, involving d orbital in transition metal ion (copper ion). Based on this theory, orbital d that has same energy will be broken by the influence of ligand field. So, it makes there is four energy level for d orbital in square planar ligand field. Square planar coordination is rare except for d9 metals ion like copper (II) ion.

    Cu 2+

    H 2O

    H 2OH 2O

    H 2O2+

    S

    -O

    -O

    O

    O

    H

    H

    O

  • Picture 3. Splitting d Orbital of Square Planar

    Electrons are located in the dx2-y2 orbital undergo repulsion of the four ligands are located on the x-axis and y; while the electron in dz2 orbital only suffered repulsion of two ligands which place on the z axis. If the ligand field is strong enough, then the energy difference between these two orbitals (orbitals dx2-y2 and dz2) becomes greater than the energy required for electron pairing.

    In such conditions, the complex will be more stable if the dx2-y2 orbitals empty and both electron should occupy eg orbitals arranged in pairs on dz2 orbitals. Thus, four ligands can be bound in a complex on the x-axis and y to be easier because it does not undergo repulsion of dx2-y2 empty orbital. Instead, ligand cannot approach the metal center through the z-axis, due to a very strong repulsion of charged two dz2 orbital electrons. Therefore only four bonds formed between the metal center with the ligand, and the geometric structure to a square planar complex. This splitting energy is same with energy in visible light, so the copper ion in copper (II) sulphate produce the blue color on that complex compound [1].

    Before doing measurement of absorbance by using UV-Vis spectrophotometer, the sample solution was diluted in order to obtain the concentration of 0.02 M; 0.04 M; 0.06 M; 0.08 M respectively. The calculation can be seen as follows:

    - Making of CuSO4 solution from CuSO4.5H2O powder

    =

    1000

    0.1 = mass

    249,5

    1000

    50

    Mass = 1.2475 gram

    So, it was needed 1.2475 gram of solid CuSO4.5H2O to make 50 mL of CuSO4 0.1 M solution.

    - Making of CuSO4 solution 0.02 M V1 x M1 = V2 x M2 V1 x 0.1 M = 25 mL x 0.02 M V1 = 5 mL

    So, in order to make 25 mL of CuSO4 solution 0.02 M , it was diluted CuSO4 0.1 M as much as 5 mL.

  • - Making of CuSO4 solution 0.04 M V1 x M1 = V2 x M2 V1 x 0.1 M = 25 mL x 0.04 M V1 = 10 mL

    So, in order to make 25 mL of CuSO4 solution 0.04 M , it was diluted CuSO4 0.1 M as much as 10 mL.

    - Making of CuSO4 solution 0.06 M V1 x M1 = V2 x M2 V1 x 0.1 M = 10 mL x 0.06 M V1 = 6 mL

    So, in order to make 10 mL of CuSO4 solution 0.06 M , it was diluted CuSO4 0.1 M as much as 6 mL.

    - Making of CuSO4 solution 0.08 M V1 x M1 = V2 x M2 V1 x 0.1 M = 10 mL x 0.08 M V1 = 8 mL

    So, in order to make 10 mL of CuSO4 solution 0.08 M , it was diluted CuSO4 0.1 M as much as 8 mL.

    The following table shows the data of standard solution absorbance using UV-Vis, but before that, it is explaining how to calculate the light intensity emitted by solution. Since I0 is the light intensity emitted by solvent and the value is represented by 100. Then absorbance is equal to - log I/Io, so A = - log I/Io A = - log I/Io 0.242 = - log I/100 0.493 = - log I/100 -0.242 = log I/100 -0.493 = log I/100 I/100 = 10M -0.242 I/100 = 10M -0.493 I/100 = 0.572 I/100 = 0.321 I = 57.2 I = 32.1 A = - log I/Io A = -log I/ Io 0.750 = - log I/100 0.993 = - log I/100 -0.750 = log I/100 -0.993 = log I/100 I/100 = 10M -0.750 I/100 = 10M -0.993 I/100 = 0.178 I/100 = 0.102 I = 17.8 I = 10.2 Here is the table of the relation of Cu standard solution with absorbance.

    Tabel 01. Measurement of standard solution

    Concentration (M) A B C D

    0.02 0.04 0.06 0.08

    I 57.2 32.1 17.8 10.2

    Io 100 100 100 100

    I/Io 0.572 0.321 0.178 0.102

  • -log(I/Io) 0.242 0.493 0.750 0.993

    Based on data above, it can be made calibration curve of standard solution between concentration and absorbance as follows:

    Graph 1. Calibration curve of Cu standard solution

    The curve of concentration toward absorbance of standard solution is appropriate to Lambert-Beer law. The absorbance increase as the increasing of concentration, in which the line equation y = 12.55x 0.008 and R = 0.9999. Therefore, the gradient is 12.55. Based on this equation, the (coefficient) of standard solution can be calculated as follow.

    Standard solution A (A= 0,242)

    A = .b.C 0,242 = x 1 cm x 0,02 mol/L

    cmLmol 102,0

    242,0

    = 12.100 L mol-1 cm-1

    Standard solution B (A= 0.493)

    A = .b.C 0,493 = x 1 cm x 0,04 mol/L

    cmLmol 104,0

    493,0

    = 12.325 L mol- 1 cm-1

    Standard solution C (A= 0.750)

    A = .b.C 0,750 = x 1 cm x 0,06 mol/L

    cmLmol 106,0

    750,0

    = 12.500 L mol- 1 cm-1

    y = 12.55x - 0.008R = 0.9999

    0

    0.2

    0.4

    0.6

    0.8

    1

    1.2

    0 0.05 0.1

    ab

    sorb

    an

    ce

    concentration

    The Relation Curve between Concentration and Absorbance of Copper

    absorbance

    Linear(absorbance)

  • Standard solution D (A= 0.993)

    A = .b.C 0,993 = x 1 cm x 0,08 mol/L

    cmLmol 180,0

    993,0

    = 12.412 L mol- 1 cm-1

    From the calculation above, it can be seen that the unit of extingsi, , is L cm-1 mol-1.

    Analysis Copper Content in Copper Ore

    From standard data above, it is obtained the calibration curve and also the line equation that can stated as follows.

    y = 12.55x 0.008

    where y represented as absorbance, x represented concentration. Therefore, by knowing the absorbance, it can be calculated the concentration. The mass of copper ores used was 0.502 grams. The absorbance of the copper ore is obtained 0.567. Therefore the concentration can be calculated as follows:

    y = 12.55x 0.008 0.567 = 12.55x 0.008 12.55x = 0.567 + 0.008 x = 0.0458

    So, the concentration of CuSO4 solution is 0.0458 M. Then, it can be calculated the mass percentage can be calculated as follows:

    % =0.10

    100%

    % =0.10 0.0458 63.55

    0.502 100%

    % = 57.979% So the mass percentage of copper ores is 57.979%.

    Analysis of Active Compound in Citra Body Lotion

    Sunscreen lotion is designed to protect skin from damage caused by UV rays from the sun. Some products of sunscreen lotion are determined the SPF (Sun Protection Factor) value which can be considered as a factor of time to protect the skin compared to exposure without any protection. The higher SPF values are considered better. But only provide protection against UV-B (ultraviolet B), it does not protect the skin against UV-A (ultraviolet A).

    Sunscreen lotions contain active compounds that can absorb UV-B rays namely oktilmetoksisinamat, butilmetoksisinamat and ethyl parametoksisinamat. In this experiment, the wavelength of maximum absorption of sunscreen lotion on the compound is measured. Sunscreen lotion that used in this experiment is Citra Body Lotion which is dissolved in ethanol.

  • In this case ethanol is used because its an organic solvent, other reason that ethanol has no

    absorption in the wavelength region of 200-1000 nm. The maximum wavelength and absorbance curve of Citra Body Lotion and Ethyl-p-Methoxycinnamate can be seen as follows.

    Picture 4.The absorbance of Citra Body Lotion

    Picture 5. The absorbance of Ethyl-p-Methoxycinnamate

    Table 2. The spectrum and effectiveness to absorb UVB of Citra Body Lotion and EPMS

    Citra Body Lotion Ethyl-p-Methoxycinnamate

    Maximum absorbance, max 0,168, 357 nm 0,544, 310 nm

    Effectivity to absorb UVB Not effective Effective

    Ethyl p-Methoxycinnamate is compound that can be isolated from Kaemferia galanga L. From the curve and the table above, it is known that the maximum absorbance of Ethyl-p-Methoxycinnamate is existed in 310 nm. This absorbance is existed in UV-B absorbance area (280-320 nm), therefore the compounds can absorb UV-B radiation. UV-B radiation is responsible for skin damage and skin cancer. So, the Ethyl-p-Methoxycinnamate can be used as sunscreen lotion. In the solution of EPMS is colorless, it because of the maximal wavelength of EPMS is 310 nm and it is not in the range of visible light that have wavelength between 400-800 nm.

    In this experiment, Citra Body Lotion that existed in the market was tested by diluting a small amount of body lotion to the ethanol. Then, it is tested by UV-Vis spectrometer and it is known from the curve that the maximum absorbances are existed in 357 nm. This maximum absorbance is not in the range of UV-B radiation (280-320 nm), but its absorbance is included in the range of UV-A radiation (320-400 nm). So, Citra Body Lotion contains active compound that can absorb UV-A radiation.

    CONCLUSIONS

    Based on the result and discussion above, so it can be conclude that:

    1. The standard curve can be obtained as follow:

  • The line equation from the curve above can be stated: y = 12.55x 0.008. From the line equation, the concentration of CuSO4 solution can be calculated that is 0.0458 M. Furthermore, it can be known the mass percentage of copper ores is 57.979%.

    2. The maximum absorbances of Citra Body Lotion are existed in 357 nm. This maximum absorbance is not in the range of UV-B radiation (280-320 nm), but its absorbance is included in the range of UV-A radiation (320-400 nm). So, Citra Body Lotion contains active compound that can absorb UV-A radiation.

    REFERENCES

    1. Anonym. 2010. Teori Ikatan dalam Kompleks. Retrieved on February 19th 2015 from: https://kyoshiro67.files.wordpress.com/2010/04/bab-iii-teori-ikatan-dalam kompleks.doc+&cd=2&hl=id&ct=clnk

    2. Muderawan, I. W. 2009. Analisis Instrumen. Undiksha Press: Singaraja. 3. Muderawan, I. W. Jurnal Praktikum 4. Tanjung, Mulyadi. 1999. Senyawa Tabir Surya yang Efektif dengan Bahan Baku Senyaea Aktif

    dari Rimpang Kencur (Kaempferia galang L). Fakultas MIPA: Universitas Airlangga.

    y = 12.55x - 0.008R = 0.9999

    0

    0.2

    0.4

    0.6

    0.8

    1

    1.2

    0 0.05 0.1

    ab

    sorb

    an

    ce

    concentration

    The Relation Curve between Concentration and Absorbance of Copper

    absorbance

    Linear(absorbance)