Lab report icp uitm






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Lab report icp uitm Lab report icp uitm Document Transcript

  • 2 | P a g e 1.0 ABSTRACT This experiment was done to determine the amount of metal Zinc in the unknown concentration of waste water samples and to determine whether they are drinkable or not. This experiment is about to determine the concentration of samples and whether the water sample is safe to drink or not. The ICP-AES instrument was used to analyse the composition of the sample and refer to WHO and USEPA health standards whether the water is potable. This experiment used 0.021 g of Zinc Chloride to dilute with 100 mL water until the concentration reach 100 ppm to prepare an aqueous Zinc chloride (ZnCl2) solution. Then, series of standard solutions needed to be prepared which has the concentration of 5 ppm, 10 ppm and 15 ppm and 20 ppm respectively. Standard solution is a solution of known concentration, used as a standard of comparison or analysis. There are 2 water samples that being tested which are sample A and sample B .This experiment was conducted by using Inductively Coupled Plasma (ICP) Mass Spectrometry, ICP model 600 series. From this experiment, the number of zinc in zinc chloride solution with concentration of 5, 10, 15 and 20 ppm were 5296,5353, 8179 and 11310 ppb respectively .Meanwhile, for the sample A and B, the number of zinc in the sample were - 0.0241907ppm and 121.583 ppm. The composition of the sample can be analyzed and the results obtained were present into a graph of IR versus Concentration Intensity of each sample was recorded and graph intensity of average composition against concentration (ppm) was plotted .Since WHO and USEPA guidelines for level of heavy metals allowed in drinking water was only 5mg/L, we can conclude that sample A is very safe to drink, consumed. and use meanwhile sample B is unsafe to drink . Overall, the experiment was a success since the objectives were achieved.
  • 3 | P a g e 2.0 INTRODUCTION Inductively Coupled Plasma -Atomic Emission Spectrometry (ICP-AES) is an emission spectrophotometric technique, exploiting the fact that excited electrons emit energy at a given wavelength as they return to ground state. The fundamental characteristic of this process is that each element emits energy at specific wavelengths peculiar to its chemical character. Although each element emits energy at multiple wavelengths, in the ICP-AES technique it is most common to select a single wavelength for a given element. The intensity of the energy emitted at the chosen wavelength is proportional to the concentration amount of that element in the analyzed sample. Thus, by determining which wavelengths are emitted by a sample and by determining their intensities, the analyst can quantify the elemental composition of the given sample relative to a reference standard. The ICP-AES is composed of two parts: the ICP and the optical spectrometer. The ICP torch consists of 3 concentric quartz glass tube and a coil of the radio frequency (RF) generator which surrounds part of this torch. Argon gas is typically used to create the plasma. An inductively coupled plasma can be generated by directing the energy of a radio frequency generator into a ICP argon gas. Other plasma gases used are Helium and Nitrogen. It is important that the plasma gas is pure since contaminants in the gas might quench the torch. Coupling is achieved by generating a magnetic field by passing a high frequency electric current through a cooled induction coil. This inductor generates a rapidly oscillating magnetic field oriented in the vertical plane of the coil. Ionization of the flowing argon is initiated by a spark from a coil. The resulting ions and their associated electrons from the coil then interact with the fluctuating magnetic field. This generates enough energy to ionize more argon atoms by collision excitation. The electrons generated in the magnetic field are accelerated perpendicularly to the torch. At high speeds, cations and electrons, known as eddy current, will collide with argon atoms to produce further ionization which causes a significant temperature raise. Within 2 ms, a steady state is created with a high electron density. Plasma is created in the top of the torch. The temperature within the plasma ranges from 6,000-10,000 K. A long, well-defined tail emerges from the top of the high temperature plasma on the top of the torch. This torch is the
  • 4 | P a g e spectroscopic source. It contains all the analyte atoms and ions that have been excited by the heat of the plasma. The detector (photomultiplier tube) is fixed in space at the far end of the spectrometer. Rotation of the diffraction grating sequentially moves each wavelength into the detector. The computer control ensures that the detector is synchronized with the grating so that the intensity at the detector at any given time is correlated with the wavelength being diffracted by the grating. The zinc wavelength is entered which we are wishes to detect into the computer, the grating sequentially moves to the specified wavelengths, and the energy intensity at each wavelength is measured to provide a quantitative result that can be compared to a reference standard. 3.0 THEORY
  • 5 | P a g e The ICP was developed for optical emission spectrometry (OES) by Fassel et al. at Iowa State University in the US and by Greenfield et al. at Albright & Wilson, Ltd. in the UK in the mid-1960s. As shown in Figure 1, the so-called ICP “torch’ is usually an assembly of three concentric fused-silica tubes. These are frequently referred to as the outer, intermediate, and inner gas tubes. The diameter of the outer gas tube ranges from 9 to 27 mm. A water-cooled, two- or three-turn copper coil, called the load coil, surrounds the top section of the torch, and is connected to a RF generator. The outer argon flow (10-15 L min-1) sustains the high-temperature plasma, and positions the plasma relative to the outer walls and the induction coil, preventing the walls from melting and facilitating the observation of emission signals. The plasma under these conditions has annular shape. The sample aerosol carried by the inner argon flow (0.5-1.5 L min-1) enters the central channel of the plasma and helps to sustain the shape. The intermediate argon flow (0-1.5 min-1) is optional and has the function of lifting the plasma slightly and diluting the inner gas flow in the presence of organic solvents. Figure 3.1 Schematic diagram of an ICP assembly showing the three concentric tubes composing the torch, the RF coil, the different plasma regions, and the temperature as a function of height above the load coil. The ICP is generated as follows. RF power, typically 700-1500 W, is applied to the load coil and an alternating current oscillates inside the coil at a rate corresponding to the frequency of
  • 6 | P a g e the RF generator. For most ICP/OES instruments, the RF generator has a frequency of either 27 or 40 MHz. The oscillation of the current at this high frequency causes the same high-frequency oscillation of electri and magnetic fields to be set up inside the top of the torch. With argon gas flowing through the torch, a spark from a Tesla coil is used to produce “seed” electrons and ions in the argon gas inside the load coil region. These ions and electrons are then accelerated by the magnetic field, and collide with the argon atoms, causing further ionization in a chain reaction manner. This process continues until a very intense, brilliant white, teardrop-shaped, high- temperature plasma is formed. Adding energy to the plasma via RF-induced collision is known as inductive coupling, and thus the plasma is called an ICP. The ICP is sustained within the torch as long as sufficient RF energy is applied. In a cruder sense, the coupling of RF power to the plasma can be visualized as positively charged. Ar ions in the plasma gas attempting to follow the negatively charged electrons flowing in the load coil as the flow changes direction 27 million times per second. Figure 3.1 shows the temperature gradient within the ICP with respect to height above the load coil. It also gives the nomenclature for the different zones of the plasma as suggested by Koirtyohann et al. The induction region (IR) at the base of the plasma is “doughnut-shaped” as described above, and it is the region where the inductive energy transfer occurs. This is also the region of highest temperature and it is characterized by a bright continuum emission. From the IR upward towards to the tail plume, the temperature decreases. An aerosol, or very fine mist of liquid droplets, is generated from a liquid sample by the use of a nebulizer. The aerosol is carried into the center of the plasma by the argon gas flow through the IR. Upon entering the plasma, the droplets undergo three processes. The first step is desolvation, or the removal of the solvent from the droplets, resulting in microscopic solid particulates, or a dry aerosol. The second step is vaporization, or the decomposition of the particles into gaseous-state molecules. The third step is atomization, or the breaking of the gaseous molecules into atoms. These steps occur predominantly in the preheating zone (PHZ). Finally, excitation and ionization of the atoms occur, followed by the emission of radiation from these excited species. These excitation and ionization processes occur predominantly in initial radiation zone (IRZ), and the normal analytical zone (NAZ) from which analytical emission is usually collected.
  • 7 | P a g e The main advantages of the ICP over the other excitation sources originate from its capability for efficient and reproducible vaporization, atomization, excitation, and ionization for a wide range of elements in various sample matrices. This is mainly due to high temperature, 6000- 7000 K, in the observation zones of the ICP. This temperature is much higher than the maximum temperature of flames or furnaces (3300 K). The high temperature of the ICP also makes it capable of exciting refractory elements, and renders it less prone to matrix interferences. Other electrical- discharge-based sources, such as alternating current and direct current arcs and sparks, and the MIP, also have high temperatures for excitation and ionization, but the ICP is typically less noisy and better able to handle liquid samples. In addition, the ICP is an electrodeless source, so there is no contamination from the impurities present in the electrode material. Furthermore, it is relatively easy to build an ICP assembly and it is inexpensive, compared to some other sources, such as a LIP. 4.0 APPARATUS AND MATERIAL
  • 8 | P a g e 1. Inductive Coupled Plasma Spectrometer apparatus 2. Accu – Jet 3. Pipette 4. Beaker 5. Plastic test tubes 6. Waste water sample 7. Zinc Chloride, ZnCl2 in solid form 8. Distilled water 9. Sample container 10. 200 ml of volumetric flask 11. 50 ml of volumetric flask 12. Tissue paper 13. Glass rod 5.0 PROCEDURE
  • 9 | P a g e 1. Mass of zinc chloride where the relative molecular mass of zinc chloride is 136.59 g/mol had been calculated. 2. The stock solution is prepared by weighing zinc chloride to be approximately 0.021 g. 3. The mass of zinc that had been weighed filled into the volumetric flask. 4. Ionized water is filled into the volumetric flask until 100 ml. 5. The solution was shake to obtain homogenous solution. 6. When the stock solution was prepared, labeled four 50 ml of volumetric flask to 5 ppm, 10 ppm, 15 ppm and 20 ppm. 7. Volume of stock solution needed had been calculated. 8. For 5 ppm, 2.5 ml volume of stock solution was filled by using accu-jet and pipette into 50 ml of volumetric flask then filled the ionized water until 50ml. 9. Step 5 is repeated for 10 ppm with 5ml volume of stock solution, 15 ppm with 7.5 ml volume of stock solution and for 20 ppm filled with 10 ml volume of stock solution. 10. After shakes the solutions, poured 2/3 solutions from flask into the several plastic test tubes. 11. Placed the plastic test tubes into ICP Spectroscopy machine to be analyses. 12. Results had been collected and discussed. 6.0 RESULT
  • 10 | P a g e 100 ml of stock solution equivalent to 10 mg/L Relative molecular mass of zinc chloride is 136.59 g/mol Relative molecular mass oh zinc is 65.38 g/mol No of mole of zinc = 10 mg L 100 ml × 100 g L = 10 mg Mass oh zinc = 136.59 g mol 65.38 g mol × 10 mg = 2089 mg = 0.021 g Volume of stock solution needed : M1 V1 = M2 V2 For 5 ppm solution, M1 V1 = M2 V2 ( 100) (V1) = (5) (50) V1 = 2.5 ml
  • 11 | P a g e PPM (Flask) Volume of stock solution needed (ml) 5 2.5 10 5 15 7.5 20 10 Figure 6.1 Concentration, ppm Average composition of Zn, Cts/S Standard deviation Relative Standard Deviation (%RSD) Blank 144.2 2.687 1.316 5 5296 14.79 0.2594 10 5353 0.11748 1.10593 15 8179 0.128964 0.819705 20 11310 0.0833189 0.390343 Sample A (0 ppm) -0.0241907 0.0463612 191.649 Sample B (0 ppm) 121.583 0.544576 0.447904 1ppm= 1mg/L Figure 6.2 1ppm=1000ppb 1ppb=1/1000 ppm
  • 12 | P a g e Figure 6.3:- A graph of average composition of Zn against concentration of solution Water sample Average zinc composition, ppm WHO and USEPA guidelines for level of heavy metals allowed in drinking water Conclusion A -0.0241907 5 mg/L @ 5ppm Safe B 121.583 Not safe Figure 6.4 y = 504.29x + 1013.5 R² = 0.9331 0 2000 4000 6000 8000 10000 12000 0 5 10 15 20 25 AveragecomposiionionZcCts/S Concentration ppm Average Compositionof Zn, Cts/S Y-Values Linear(Average composiion ion ZcCts/S)
  • 13 | P a g e 7.0 DISCUSSIONS The objective of this experiment was to determine the amount of metal in the waste water sample A and sample B. The inductively Coupled Plasma (ICP) was chosen as a method of this experiment. Manufacturing activities in industrial areas can introduce dangerous pollutants into waste water system. At the end of this experiment, the result of waste water can conclude whether the water sample is safe to drink or not. There were several advantages that supports the using of ICP which were ICP has a low limit of detection, high stability leading to excellent accuracy and precision, high electron density, high temperature ( 7000 K – 8000 K ), easy to use, fully automated, uses small amount sample volumes and applicable to the refractory elements. The powder cannot be used as a sample. This is due to the ICP instrument want to detect the ions in the samples because the metals are soluble in water as ions. Zinc is used as reference metal in this experiment. If water sample containing higher concentration of zinc, it is not safe to drink. The example of water sample is water river, sea water and other water. Water has a simple molecular structure which composed of one oxygen atom and two hydrogen atoms. Each hydrogen atom is covalently bonded to the oxygen via a shared pair of electrons while oxygen has two unshared pairs of electrons. So that, there are four pairs of electrons surrounding the oxygen atom, two pairs involved in covalent bonds with hydrogen and two unshared pairs on the opposite side of the oxygen atom. The water become acidic when the water sample contain zinc atom. This is due to zinc atom are attached at oxygen and hydrogen atoms. The water becomes unsafe to be consumed or to drink. First of all, the stock solutions must be prepared. There are five solutions needed to test in the ICP-AES method in order to achieve calibration curves. In order to prepare zinc chloride (ZnCl2) solution, 0.0021 g of Zinc Chloride is used to dilute with 100 mL until the concentration reach 100 ppm. By using the same solution, the other solutions needed to prepare such as 10 mL is taken from the 100 ppm solution to prepared 20 ppm solution. For second solution,7.5 mL is taken from the 100 ppm solution to prepared 15 ppm solution. Then, 5 mL is taken from the 100 ppm solution to prepared 10 ppm solution. And lastly 2.5 mL is taken from the 100 ppm solution to prepared 5 ppm solution.
  • 14 | P a g e From a graph in Figure 6.3, sample B contain an extremely high in average of zinc component which is 121.583 ppm. This is exceeding the WHO and USEPA guidelines for level of heavy metals allowed in drinking water. The average composition of zinc component in sample A is lower than sample B with -0.0741907ppm. Thus the sample A is drinkable. This is due to sample A containing no zinc element or presence in small quantity. The contamination in the sample cell affected the reading amount of metal present in water. Regarding to the result, the sample B is not safe to drink but for a sample A considered as a safe drinking water. This experiment was succeed when the main objective was fulfilled. But during conducting this experiment, there were several mistakes done regarding to unability to get correlation as 1. The correlation that we got was 0.9992. This is totally due to human error such as the beaker is not fully clean. The value of zinc chloride (ZnCl2) must be accurate such as 0.021 g when weigh that solution. When measure the stock solution in flask, the reading must meniscus. One way to discharge unsafe wastewater is to treat the wastewater. Modern technologies have done wonders in terms of treating unsafe drinking water by producing a method that is used to remove heavy metals, in this case zinc, by hydroxide precipitation. This method applies the concept of adjusting the pH of the water so that the metals will form an insoluble precipitate. Once the solid is formed, it can be removed by filter process and the water can be discharged. This method is dependent upon two factors: the concentration of the metal and the pH of the water. Heavy metals are usually present in dilute quantities i.e. in the range of 1 to 100 mg/L and its pH values lies at the neutral level or acidic. Both of these are disadvantageous with regard to metals removal. That is why caustic is added. When caustic is added to the dissolved metals, metals would react with the hydroxide ions to form metal hydroxide solid
  • 15 | P a g e 8.0 CONCLUSION From the discussion, it can be concluded that the experiment was successfully conducted and the purpose of this experiment is to determine whether the water samples are safe to drink has been achieved. We can determine the presence of metal Zinc in waste water unknown sample A and B by using Inductively Coupled Plasma (ICP) method. The value of correlation from this experiment is 0.9992. Thus, this shown that the best correlation is 0.9999 or 1.0 which show the almost accurate concentration of standard solution. Mainly we are looking at the concentration of dissolved metal element, zinc in the water samples. ). From the data, graph of Cts/s versus concentration of Zn (ppm) has been plotted, the concentration of zinc in Sample A and B have been determined. There are two samples, A and B. The average compositions of zinc, ppm or mg/L for Sample A and Sample B were -0.0241907ppm and 121.583ppm respectively, Sample B having the higher composition of Zn than composition in sample A. According to WHO and USEPA, the allowed composition of zinc in drinking water is 5 mg/L or ppm. From the results we have concluded that the amount of zinc in sample B was too high and would most probably kill anyone who would consume them if not seriously harm them or give them diarrhea. So that would be no, both water samples are not safe to drink. For the sample A, it is safe to be consumed since it is not exceeding the WHO and USEPA guidelines for level of heavy metals which 5ppm. Sample B is suitable for drinking purpose where the standard value of Zn content is allowed by World Health Organization (WHO) drinking water standard. Meanwhile, Sample A cannot be drink because the Zn value in the sample excess the standard regulation from WHO. The inaccuracy results occurred in this experiment may cause by some errors like parallax errors, equipment efficiency or problem and other things. However, we realized that we have faced a lot of problem and made some errors while we prepared this experiment. Even though the result was not accurate since some errors had been made during the experiment and different from the theory as stated in discussion section, we still consider this experiment has been a success since the objective of this experiment was achieved. After this experiment was carried out, we had learnt some experiences and new knowledge from it. We had understood the concept of Inductively Coupled Plasma (ICP) which is used to analyse the composition of the sample A and sample B. 9.0 RECOMMENDATIONS
  • 16 | P a g e 1. The plasma must be insulated from the rest of the instrument in order to prevent short circuiting and as well as meltdown. 2. The sample is discouraged for a solid sample as clogging of instrumentation may occur. 3. Plasma ICP is used because the source is under atmospheric conditions 4. Carefully handle the bottle sample to avoid any accident occur. 5. Labeled the bottle sample according the concentrations to avoid mistake while conducting the experiments. 6. Carefully pour the chemical and it is very good to wear hand sock to avoid injured. 7. 10.0 REFERENCES 1. 2.[Accessed 24 April 2014] 3. (Robert A. Mayers, 2012, Encyclopedia of Analytical Chemistry) 4. [Accessed 23 April 2014] 5. Accessed 22 April 2014] 6. Accessed 20 April 2014] 7. Accessed 27 April 2014] 8. Accessed 21 April 2014] 9. World Health Organization [Online] Available at: Accessed 23 April 2014] 11.0 APPENDICES
  • 17 | P a g e Figure 11.1:The Inductively Coupled Plasma (ICP) Mass Spectrometry,ICP 600 series