Determination of Calcium - Coursework Example

 Determination of Calcium Introduction Calcium doesn’t exist as a free metal in nature because it is highly reactive. Therefore, it occurs in a large quantity as compounds: such as calcium trioxocarbonate (IV), CaCO3 in marble, chalk, aragonite, calcite and coral; as calcium tetraoxosulphate (VI), CaSO4, in gypsum and anhydrite; as a double trioxocarbonate (IV), CaCO3.MgCO3, in dolomite; as calcium fluoride, CaF2, in Fluorspar. Bones and teeth contain calcium tetraoxophosphate (V) (Cox, 2004) 　　　　　　　　　　　　Image of Calcium (Calcium Image Source: The Internet ENCYCLOPEDIA OF SCIENCE) Explanation of Calcium imaging Calcium imaging requires some high-tech processes: the following procedures are highlighted in Biophysical Journal (Charles et al, 2000). The expressions below are quoted directly from the Biophysical Journal. “Samples of calcium were cooled to 10°C for 10 min (to prevent dye internalization into organelles) before staining with fura-2/AM (5 mM) and 0.25% Pluronic-127 for 30–60 min at room temperature, followed by a 30-min recovery in EBSS at 37°C. Images were acquired using a high-speed Photometrics CCD camera (frame transfer EEV37 chip) on an inverted Zeiss microscope, controlled by Inovision software on a Silicon Graphics workstation. Coverslips were mounted on an open-welled chamber. The cells were bathed in pH-controlled EBSS and maintained at 37°C. Ratio pairs of 340- and 380-nm excitation were collected for some experiments, with emission passed through a rhodamine filter. Using this acquisition protocol, ratio pairs could be collected approximately once a second. Because the BK-induced calcium waves are typically very fast, faster imaging was necessary to resolve the geometry of the calcium wave propagation. Faster imaging was possible using only the 380-nm excitation wavelength, in which images could be obtained every 65 ms. Cell exposure during excitation was kept to a minimum by using 4 3 4 binning (resulting in 128 3 128 images) and increased gain settings, but always maintaining at least a 5-to-1 cell-to-background intensity ratio. BK was added in 20-ml aliquots to the cell chamber, so that the exposure was nearly instantaneous but with as little cellular disturbance as possible.” (Charles et al, 2000). Physical and chemical properties of group II elements Calcium is an element in group II of the periodic table. Hence, it shares similar physical and chemical properties with other elements in this group; for example, Potassium (Wells, 1984). Physical properties: Calcium is a silvery solid, metal and has a melting point of about 64 and boiling point of 773. It can act as a reducing agent. And it reacts slowly with water. Calcium is a divalent element with each of its atom having two valence electrons. Ca Ca2+ + 2e- Chemical properties: Calcium liberates hydrogen from water and forms a hydroxide. Ca(s) + 2H2O(l) Ca(OH)2 (aq) + H2 (g) CaO (s) + H2O Ca(OH)2 (aq) Calcium trioxonitrate (V) salts decompose readily on heating to give oxides, oxygen and the brown gas, nitrogen (IV) oxide (Cotton et al, 1999). Ca(NO3)2 (s) heat 2CaO (s) + O2 (g) + 4NO2 (g) Calcium trioxocarbonates (IV) are insoluble in water. They decompose on heating to give oxides and carbon (IV) oxide. CaCO3 (s) heat CaO (s) + CO2 (g). Analysis of Calcium 1. Flame Test: This is a procedure used in Chemistry to detect if some impurities are present in a particular substance. The test itself is simple and requires a few materials. Some of the materials needed are a nichcrome or Platinum wire, concentrated hydrochloric acid and a Bunsen burner that produces a flame. Flame test procedure is as follows: Clean a platinum wire by dipping it into a concentrated hydrochloric acid and then holding it in a Bunsen flame. This procedure must be repeated until the wire produced no color. When the wire is clean, moisten it again with some of the acid and dip it back into the acid and put the wire with the solid on it into the flame and watch the color. If the color produces is orange-red, it signifies the calcium under analysis is pure and contains no impurities (Heinemann 1984). 2. Flame photometry: This is an atomic emission technique for detecting metal salts, especially that of Calcium, Sodium and Potassium. This is carried out by measuring the flame emission of the solutions containing the metal salts. The procedure for flame photometry is as follows: Solutions of the metal salts are aspirated into the flame. The hot flame makes the solvent of the solution to evaporate and atomizes the metal so that valence electrons are excited to an upper state. Then light, which is characteristic of the metal in salt, is emitted as the electron goes back to the ground state. One could use optical fibers to select the emission wavelength for a certain metal and compared the wavelength with that of a standard to confirm its quality. This procedure is simple, cheap and fast (Harris 1995). 3. High Performance Liquid Chromatography (HPLC): is a very useful analytical tool to separate, identify and quantify substances. It is helpful in determining the quality of a particular compounds as its constituents are analyzed and investigated for purity. The method for carrying out this analysis could be described as follows: The sample to be analyzed is introduced in small volume into the stream of mobile phase in the column. Therefore, some physical or chemical interactions would slow down the analyte’s motion through the column. The extent of slowness depends on the nature of analyte, stationary and mobile phases compositions. And each component of the analyte would come out of the column at different retention time, which is defined as the time it takes for the component to get out of the column. HPLC separates a compound to its constituents in their purified states. In the case of a calcium compound, say chalk, once the solution has been introduced into the column in small volume, the compound journeys through the columns until its constituents are separated based on their retention time (Mant & Hodges 1991) 4. Simple Chromatography: Calcium compounds could also be analyzed using simple chromatography techniques. The compound could be dissolved in a solvent and allowed to move up a chromatography paper until all the components are separated along the paper. Advantages and disadvantages of calcium analysis techniques 1. Easy to use: Some of the techniques explained above concerning the analysis of calcium are easy to use. That is, they don’t require elaborate procedures to apply them in determining the quality of calcium. Examples of these are the flame test, simple chromatography, flame photometry. 2. Inexpensive: Flame test, simple chromatography and flame photometry are cheap; they do not require expensive set of equipment to carry out. On the other, High Performance Liquid Chromatography is expensive, and it needs expensive laboratory set-up to be successfully carried out (Knox & Kauer 1989). 3. High degree of quality: Though useful, flame test and simple chromatography may not produce high quality of analysis. But Flame photometry and High Performance Liquid Chromatography would definitely produce high-quality separation and analysis (Schoeff & Williams 1993). Conclusion Based on the above research, it is interesting to choose Flame photometry as the appropriate technique for analyzing calcium. The reason for this is that it is cheap, easy to use and produces a high quality of analysis. The other techniques are either too expensive to use, like High Performance Liquid Chromatography or they produce not-so-high quality of separations, like Flame test and simple Chromatography. References 1. Schoeff, MS and Williams, RH 1993, Principles of Laboratory Instruments, Mosby, St. Louis. 2. Mant, CT and Hodges RS 1991, eds. High-Performance Liquid Chromatography of Peptides and Proteins: Separations, Analysis, and Conformation, CRC Press: Boston. 3. Knox, JH and Kauer, B. 1989, High Performance Liquid Chromatography, Wiley Interscience: New York. 4. Harris, DC 1995, Qualitative Chemical Analysis, 4th Ed., W.H. Freeman and Company, New York. 5. Heinemann, SB 1984, Chemistry Experiments for instrumental methods, Wiley, New York. 6. Charles CF, Boris S, Ion IM, James, W, James CS and Leslie, ML 2000, “An Image-Based Model of Calcium waves in Differential Neuroblastoma Cells,” Biophysical Journal, Vol. 79 no. 1, pp. 163-183. 7. 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