Forensic Food Analysis - Assignment Example

Name Course Date Flame photometry Introduction Sodium and Potassium are two essential elements that perform important biological functions in human body, but they are only required in relatively small quantities. Sodium plays a critical role of maintaining normal blood pressure and blood volume and enables the normal function of the nerves and muscles. But high intake of sodium leads to high blood pressure in some people or a serious build up of fluid in people that result in cardiovascular disease, congestive heart failure, cirrhosis or kidney disease (Grosvenor & Smolim 2009; Sucio 2014). Potassium is critical to heart function and plays a major role in skeletal and smooth muscle contraction which makes it essential for normal digestive and muscular function. Excess amount of potassium leads to palpitations, malaise and muscle weakness. Extreme amount of potassium causes hyperkalemia and fatal abnormal heart rhythms (arrhythmia) in smaller amount. It is therefore important to maintain sufficient amount of these elements in the body to maintain healthy state. But excesses of the elements can lead to health problems. The major source of daily intake of sodium is sodium chloride (table salt) (Williams & Hopper 2015). Flame photometry is atomic spectroscopy that is used to determine the concentration of alkali metal and alkali earth metals ions like potassium, sodium calcium and lithium. The technique is performed by measuring the amount of light that metal species emit in a flame after absorption of energy in form of chemical or heat energy (Aulisa & Gilliam 2015). It is based on the principle that alkali metal ionizes, take energy from the flame and produce light when it is exposed to non-luminous flame. The light emit has a unique wavelength as the excited atom goes back to unexcited state. The emission intensity is directly proportional to the concentration of the solution. Flame photometer is shown in the figure below. Figure 1: Flame Photometer The flame provides the thermal energy needed by the metal to dissociate. In this excitation state, the atom is unstable, and the light absorbed due to the electrons excitation is measured using direct absorption method. But as the atom loss energy, the atom move from the excited state to ground state which is followed by emission of radiations that lies within the visible portion of the spectrum. Direct absorption method measure the light absorbed because of excitation of the atom while emission technique is used to measure the intensity of the emitted electrons, such that each element emit light with specific wavelength (Brimer 2011). This experiment involves determination of sodium and potassium in a low salt soy sauce sample. Low salty soy sauce was diluted and filtered before testing using flame photometer. Objectives The man objectives were: To determine the sodium and potassium in low salt soy sauce using flame photometry. To use calibration curve for quantification of sodium and potassium. Methods The experiment began with preparing standards solutions of potassium and sodium using deionized water (deionized water was used instead of distilled water to prepare all solutions because distilled water has too much sodium in it). Standard solutions of sodium with 5, 10, 15, 20 and 25 ppm were prepared from 1000ppm/μl solution and the standard solutions of potassium with 3, 6, 9, 12 and 15 ppm were also prepared from 1000ppm/μl solution which has been summarized in the following table. Table 1: The table for preparation of standard solution Na K Conc. Required (ppm) Amount required in 100ml from 1000ppm/ μl Conc. Required (ppm) Amount required in 100ml from 1000ppm/ μl 5 500 3 300 10 1000 6 600 15 1500 9 900 20 2000 12 1200 25 2500 15 1500 Measurement was conducted using flame photometer. This began by ensuring that the photometer was connected to the power supply, gas and air before putting the flame photometer on and leaving it for 5-10 minutes to warm up. A filter in place of monochromator was set at the correct wavelength before introducing deionized water into the atomizer. Zero suppression controls were adjusted so as to bring the reading of the instrument to zero. Next, the most concentrated standard solution (25ppm) was aspirated and the uppermost scale was adjusted by turning the inner knob to attain the maximum scale. Deionized water was also aspirated to ensure that the instrument was reading zero and the steps were repeated until the readings were within the scale. Then different readings were taken by aspirating different solution standards with low concentrations. The calibration curve was then plotted using concentration of the solution and the instrumental readings. The system was cleaned by aspirating distilled water for 5 minutes before repeating the same steps for the standard solutions of potassium. A pilot dilution of 1/2000 was prepared and ran at appropriate wavelength before making calibration curve to test if the pilot dilution fits and the range suitable. Finally, the solution with unknown concentration (Soy Sauce) was determined using the analytical curve or calibration curve. Everything was run three times and the average was taken before making calibration curve. Results The results obtained from the two tests were recorded on the tables as shown below. Table 2: The table for Sodium- Pilot Standard Conc. (ppm) Flame Photometer Reading 1 Flame Photometer Reading 2 Flame Photometer Reading 3 Mean 0 0 0 0 0.00 5 23 23 25 23.67 10 45 43 45 44.33 15 65 61 65 63.67 20 84 77 83 81.33 25 101 93 100 98.00     Amoy- 1/2000 88 84 89 87.00 Table 3: The table for Potassium- Pilot Standard Conc. (ppm) Flame Photometer Reading 1 Flame Photometer Reading 2 Flame Photometer Reading 3 Mean 0 0 0 0 0.00 3 31 33 32 32.00 6 57 60 58 58.33 9 85 87 84 85.33 12 109 113 110 110.67 15 133 135 134 134.00 Amoy- 1/2000 17 20 18 18.33 Graphs were obtained by plotting the average readings against the standard concentration on the excel sheet. The graphs are shown below. Figure 2: The curve showing the relationship between the concentrations of sodium with instrument readings The average reading of the unknown solution was obtained and that reading that from the instrument was 78. This corresponds to the concentration of 23.4 ppm. The graph for the data obtained from the potassium solution is shown below. Figure 3: The curve for the concentration of potassium against the readings from the instrument The average reading from the instrument was 18.33 which corresponds to the concentration of 1.5ppm Calculations Concentration of flask solution: = Discussion When sodium and potassium are introduced into the flame, they emit radiation in form of coloured light (red for potassium and yellow for sodium); this is the basis of qualitative flame tests, which is used in flame photometry. Basically, it is the intensity of radiation emitted by atoms that is measured, and has direct proportionality to the concentration of metal ion that is emitting the radiation. Quantitative analysis is performed through measurement of the emission of the flame by the solution that contains metal ions (Brimer 2011). When solution was aspirated into the flame, the solvent evaporated, the atoms were excited and the valence electron was excited to an upper state. Light radiation was also produced at characteristic wavelengths for the two metal ions as the electron went back to the ground state. Quantification of analyte metal in the solution sample was made possible by comparing the light intensities of the unknown solution to that of standard solutions assists, which can be read from the graphs (Brimer 2011, 251). When the solution was exposed to the flame, the solvent evaporates while the metal ions were left in the flame. At this point, the ions evaporates into vapour form and dissociate to from constituent atoms. Due to the energy from the flame due to increase in temperature (temperature of the flame is approximately 18000C), a fraction of the atoms is excited and gets excited electronically to higher energy level. Inside the flame, the equilibrium Na ↔ Na+ + e- is established. Due to their unstable state, the excited atoms fall back to the ground state by emitting energy in form of light radiation with a characteristic wavelength (K-766nm; Na-589) (Gadag 2010). The emitted light intensity is proportional to the number of atoms, which in turn is proportional to the concentration of solution sample fed into the flame. Color filters the light emitted and allow light from K+ and Na+ to pass through. Thus their concentration can be measured from the sample (Gadag 2010, 313). The radiation intensity as measured by the detector is related to concentration and efficiency similar to Beer’s relation, E = kαc Where k = Constant E = Detector response α = the efficiency of the atomic excitation C = Concentration of the solution Thus the detector response is directly proportional to the concentration of the solution and the efficiency of the instrument (Gadag 2010, 313) The results obtained in this experiment for the unknown concentration of soy sauce solution (Na = 23.4ppm and K = 1.5ppm) appear to be reasonable, taking into account the fluctuation that exist on the digital read out of the photometer. The graph appears to be in proper and is within the expected range, taking into account the R value. The main sources of errors relates to the photometer. The photometer reading was fluctuating, but this was minimized by allowing the solution to flush the photometer for some few seconds before taking the reading. Nevertheless, the right amount of flush time may not have been used. Another concern has to do with cleanliness of the apparatus. It is likely that the apparatus may not have been cleaned properly in the past, thus residue may have be present in the photometer capillary tube. Another source of error is interference. There are two types of interference in this method: chemical interference and spectral interference. Chemical interference occurs due to the reaction between the anylate and the interference. This reduces the concentration of the anylate in the flame. Spectral interference occurs due the scattering effect of the potential products in the flame and the molecular species absorption in the flame (Stern 2013). Applications The flame photometry technique is used in qualitative and quantitative applications. Monochromators in flame photometer produce radiations of specific wavelength that can be used in detecting the amount and the types of metals found in a sample. This assist in determining the presence alkali metals are crucial in agriculture. The type and amount of fertilizers required by the soil is analyzed using flame test soil analysis. In health sector, the amount of K+ and Na+ ions in the body fluids, heart and muscles is determined by adding the blood serum into a solvent and aspiration into the flame. In addition, the technique can be applied in the analysis of fruit juices, alcohol beverages and soft drinks using flame photometry (Sharma 2005). Advantages Flame photometry method has the following advantages This analytical test technique is not expensive. It is quick, sensitive, convenient and selective to parts per million to parts per billion The analysis of the elements like alkali metals is done easily with most convenient and reliable technique (Robinson et al. 2004; Sharma 2005) Disadvantages Although this technique can be used in a wide range of applications in chemistry analysis, it has a number of disadvantages that are explained below. The metal ion concentration cannot be determined accurately. Determination of the concentration of ions using this technique requires a standard solution with known molarity, the concentration of the ions corresponds to the spectra emitted. It is not possible to determine the molecular structure of the compound in the test sample. With high concentration of the solution, it is not east to get accurate results of the ions in the sample solution. The elements like halides, carbon and hydrogen cannot be detected through this method because they have non-radiating nature (Sharma 2005). References Aulisa E. & Gilliam D. (2015). A Practical Guide to Geometric Regulation for Distributed Parameter Systems, Monographs and Research Notes in Mathematics, CRC Press Brimer, L. (2011). Chemical food safety. Wallingford, Oxfordshire: CABI. Gadag T. (2010) Engineering Chemistry, I. K. International Pvt Ltd Grosvenor, M. B., & Smolin, L. A. (2009). Visualizing nutrition. Hoboken, N.J: Wiley, 253. Williams, L., & Hopper, P. (2015). Understanding Medical Surgical Nursing. Philadelphia: F.A. Davis Company, 80 Robinson J. W., Frame E. M. S., Frame II G. M., (2004) Undergraduate Instrumental Analysis, CRC Press Sharma d. (2005) A Handbook of Spectroscopy, Mittal Publications Stern, A. C. (2013). Air pollution: Volume 2. Burlington, VT: Elsevier. Sucio D. (2014) Rays of Sunshine Revised and Expanded, Author House Read More