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Garcia 1Jasmine GarciaEmily TiberanoAmber Rolland02/21/17Spectrophotometric Determination of a Food Dye Lab ReportIntroduction:The purpose of this lab was to determine the amount of food dye present indifferent popular drinks. Food dyes are present in different American drinks in varying amounts.The idea is that each dye has a unique “fingerprint” that can be detected throughspectrophotometric analysis. Absorbance of light is directly proportional to concentration; thatallows for determination of different concentrations of food dye in different drinks. The Beer-Lambert Law equation shows the relationship between molarity and concentration:A=εbcA is the absorption,εb is the slope and c is the concentration. When a graph relatingconcentration and absorbance is graphed it results in a straight line. The concentration of anunknown can be found by using the equation and absorbance of the unknown. This equation isproduced in the calibration curve. The maximum absorption is the most important thing in thegraphs because it’s where most of the light gets absorbed. It provides maximum absorbance asmolarity changes and minimizes the impact of error. It is also important for futuremeasurements. The more molecules that are present, the more light is absorbed. Molarity fordiluted solutions can be easily found by using the following equation (where M is molarity and Vis volume):M1V1=M2V2Food dyes are used to distinguish different foods and flavors of things that would otherwise alllook the same.Procedure:In the first part of the lab, my partner and I made a stock solution using FD&C BlueNo.1. In the second part, we diluted our stock solutions so that they contained varying amountsof the stock solution and therefore different molarities. Next, we created a calibration curve todetermineλmaxand an equation for concentration of blue dye. Once we had a calibrationcurve, my partner and I determined the concentration of a solution that had only the FD&C BlueNo.1 dye and then we tested another solution that contained FD&C Blue No.1 and FD&C YellowNo. 5. The blue dye had a molar mass of 792.86 g/mol.
Garcia 2Safety:Nothing in lab should be consumed, smelled directly, or touched directly. Wear glovesand handle glassware with care.My class decided to investigate the following questions: How do we determine the amount offood dye in the unknown? What can influence our results? How does use of multiple dyes affectsolutions? My question was:Are the concentrations of food dyes safe, and if so, when do theybecome toxic?Experimental:Preparation of Stock Solution: The FD&C Blue No.1 dye was in powder form, which was a darkpurple color. I usedM1V1=M2V2to produce the target molarity. The target molarity for theblue dye was3.65x10−5M.