Aas Lab Report

Abstract The objective of this experiment is to determine calcium content in commercial supplement tablets. The quantity of calcium per tablet that is stated at the supplement bottle was to be 200mg. To investigate this statement, we need to determine experimentally the actual content of calcium in the supplement tablets. The experiment was conducted by using atomic absorption spectroscopy analysis. Before running the analysis using AAS, first a series of standard solutions based on calcium concentration was established. A 50ppm stock solution of calcium is prepared in 100mL flask using CaCl2.2H2O salts. Thus we need exactly 5mg of calcium, Ca to be dissolved in the 100mL flask to get 50ppm. From the stock solution, a series of standard solution of 25ppm, 12.5ppm and 6.25ppm was prepared by diluting a specific volume from the stock solution in three individual flasks to the respected concentration. The volume of 50 ppm needed to be dissolved in 50 mL flask to get 25 ppm, 12.5 ppm and 6.25 ppm are 25 mL, 12.5 mL and 6.25 mL respectively. Further aspect of this experiment is the evaluation of the effect of pH on the solubility of the calcium tablets and the efficiency of digestion in the human body. In the second sets of measurement, five solutions of the dissolved tablets with known pH level from 0 to 5 are analyzed using the AAS. From the AAS analysis, the absorbance value for the solutions with pH 0, 1, 2, 3, 4 and 5 are 0.1441, 0.1676, 0.3650, 1.4077C, 1.4018C and 1.3923C respectively. From the absorbance reading obtained, using the interpolation and extrapolation of the calibration curve, we get the concentration of Ca in the solutions with pH 0, 1, 2, 3, 4 and 5 to be (4.62, 5.64, 14.28, 59.91, 59.65 and 59.23) ppm respectively. The highest concentration of Ca between the five solutions is in pH 2 with 59.91 ppm. It shows that pH 2 is the optimum pH level in dissolving the Ca tablet. From 59.91 ppm, we get the amount of Ca in the tablet to be 59.91 mg. This result disagree with the claim from the commercial tablet box where the amount of Ca to be 200mg per tablet.

Introduction Atomic line absorption spectra are used for analysing various metals. Atomic absorption spectrophotometry ("AAS") offers sensitivity, selectivity and simplicity and was developed by CSIRO Melbourne scientists around 1955. "AAS" is an important tool in analytical laboratories. Using this technique, samples of water and soil can be tested for various metal ion levels. Metals commonly analysed include sodium, potassium, magnesium, zinc, chromium, mercury, cobalt, copper, cadmium, There are a number of situations where elemental composition is important – e.g., how much iron in an ore sample, how much lead in your drinking water, calcium in intracellular fluids. In a sense, it’s the simplest type of analysis, since there are only about 120 possible analytes. But to do the analysis, the sample has to be completely destroyed (chemically and physically) and reduced to individual gas phase atoms (or related species, like ions) in well defined states that can do spectroscopy on. Obviously this requires a very highly energetic environment and a lot of modification of the sample, both of which lead to a number of complications. These problems can be addressed if their presence is anticipated and the physical mechanism is understood. In addition to giving you a little experience with AAS (Atomic Absorption Spectrophotometry) iron and arsenic.

Atomic Absorption Spectroscopy (AAS) is use in order to measure the concentration of gasphase atom by absorbing of light which is ultraviolet light or visible light that will excite an electrons from lower energy levels to higher energy levels. All particular elements that being involves in experiment will be analyzed using an instrument called atomic absorption spectrophotometer. The process of atomic absorption spectroscopy involves two steps which are atomized the sample and absorbed a radiation from the light source by free atoms. At the first stage of the mechanism, the analyte atoms or ions must be vaporized in a flame or graphic furnace. The flame is lined up in a beam of light of the appropriate wavelength. Atom will undergo a transition from the ground state to the first excited state because of flame. When atoms make their transition, they absorb some of the light from the beam. The basic structure of atomic absorption spectrophotometer are hollow cathode lamp, an atomizer section for atomizing the sample, a monochrometer for selecting the analysis wavelength of the target element and also a detector to convert light into an electrical signal. Hollow cathode lamp is consists of hollow cathode, anode, neon or argon gas.

Objective

1. To determine the commercial calcium supplement by Atomic Absorption Spectrophotometry. 2. To find out how to make up a 100 mL 100ppm calcium stock solution 3. How to dilute this solution to give a series of standard solutions (20, 15, 10 and 5 ppm) to be used in the calibration of the spectrometer.

Theory