Absorption Spectroscopy Lab Abstract: The concentration of the red dye in the Gatorade sample was 6. 12×10^-5 g/mol. Also, from the data, we can detect that an average human being weight 60 kg, would have to consume 11,849,510 g of this sample to reach the LD50. Using Absorption Spectroscopy to determine the molar concentration of a solution is affective when there is a stock solution with a known concentration, which in this case is Red dye #40. Introduction: There are some dangers posed by the chemicals found in the food we eat and in drinks. Measuring the amounts of these dangerous chemicals is very important when determining their safety.
Food safety is a continuing public concern in the United States, and the food nearly everyone eats has been processed in some form. During processing, chemicals are added to improve food safety by retarding spoilage and preventing the growth of unwanted organism. Some of the chemicals may be deceiving and this is our primary concern to be aware of. Chemicals that are dangerous in large amounts can be quite beneficial in small amounts. Measuring the amounts of chemicals present in food and drugs is really important, and the common way to measure this done by using absorption spectroscopy.
A most common chemical in the food we eat is food dye. The FDA is in charge of assessing and certifying the safety of chemicals that are added to food and used in drugs everyday, and to this day only nine food dye chemicals are safe for use. The dyes are made up of small organic molecules that absorb light in the visible region. The purpose of this experiment is to identify the amount of dye present in a food product and evaluate its safety. The objective is to prepare a series of standards from a known solution using a serial or parallel dilution, prepare an unknown sample, measure absorbance of all samples, determine olar absorptivity of a food dye, and determine percent composition of the food dye in a food sample by using Beer’s Law A=EbC to analyze the sample, which was Gatorade, with red #40 dye. Results: Known Concentrations Results: 5mL of Red #40, with Molarity of 4. 03×10^-5 | |Dilution |Samples | | | |Cuvet |Dilution factor |Distilled Water |Molarity |Absorbance |Wavelength | |1 |1:1 |5mL red #40 |4. 03×10^-5 |0. 932 |498 nm | |2 |1:3 |10mL red #40 |1. 34×10^-5 |0. 208 |500 nm | |3 |1:4 |15mL red #40 |1. 01×10^-5 |0. 174 |509 nm | |4 |1:5 |20mL red #40 |8. 06×10^-6 |0. 11 |500 nm | |5 |1:6 |25mL red #40 |6. 2×10^-6 |0. 09 |498 nm | |5 |1:7 |30mL red #40 |5. 76×10^-6 |0. 075 |519 nm | |Linear Plot of Diluted Samples: Slope: y=mx+b y=25335x – 0. 0895 R^2=. 9958 25225—->Molar Absorptivity Gatorade Sample: Max Absorbency= 2. 476 Max Wavelength= 490 nm Dilutions: 3mL gatorade: 5mL of distilled water Absorption= . 93 Concentration: A=EbC A=. 93 E=25335 b=1 C= . 93/25335= 3. 67×10^-5 3. 67×10^-5 x 5/3 = 6. 12×10^-5 *More dye in Gatorade sample than the known Red #40 dye Ld50: Average Human= 60 kg Molecular Weight of Chemical 496. 42 g/mol 496. 42 g/mol= 60,000 g x 6/ X(Mol) X(Mol)= 725. 19
V=Moles/Concentration of Gatorade = 725. 19/6. 12×10^-5 = 11,849,510 g Calculations: The equations used for this experiment was: Beer-Lambert Law: A=EbC M1 x V1= M2 x V2 slope of line: y=mx+b Molarity=mol/L Molarity: Ex.. M1= 4. 03×10^-5 x 5mL= M2 x 20 mL M2= 1. 01×10^-5 Slope of the line: y=mx+b Ex.. y=25335x – 0. 0895 Molar Absorptivity= 25335= E Beer-Lambert Law A=EbC A-Absorption E-Molar absorptivity b=path length (1 cm) C= Concentration Ex.. Finding Concentration in the Lab A=. 93 E=25335 b=1 .92= 25335 x 1 x C C= 25225/. 92= 3. 67×10^-5 LD50 of Gatorade: 496. 42 g/mol= 60,000 g x 6/ X(Mol) X(Mol)= 725. 9 V=Moles/Concentration of Gatorade = 725. 19/6. 12×10^-5 = 11,849,510 g Discussion: The dye of the gatorade sample came out to be 6. 12×10^-5. To read an LD50 of this sample you would have to consume 11,849,510 g of this sample to have a lethal dose. This answer could be slightly different considering on what human weight you are testing the sample on. This lab was very intriguing when finding the dye of your unknown sample (gatorade) through the known dyes. Absorption Spectroscopy is a very reliable way to detect the concentration solutions only if there is a stock solution with a known concentration.
The computer spectrometer is very helpful in performing this process to find wavelengths the solution is absorbing and emitting, we can easily find concentration. The Absorption Spectroscopy used Beer’s law equation A=Ebc, to evaluate the concentration of the Gatorade dye that was being tested. The graph of the known samples, created a straight line, y=mx+b giving us the molar absorptivity to help come to the conclusion of the concentration of our dye. Using the cuvets, tested the wavelengths and the absorption of the known and unknown samples to also help come to the conclusion of our sample dye.
