To print the story please do so via the link in the story toolbar. The color of the dye solution depends on the light that is reflected and absorbed.

The purpose of this lab was to determine the unknown dye concentrations in solutions using a spectrophotometer. If we determine the maximum absorbance of different food dyes, then one will be able to determine the idnenty of the food dye in an unkown substance. To begin the experiment you must use a black block to calibrate absolute absorbance and use water to calculate the value for no absorbance.

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Dilute the stockroom dye with a ration so that there will be one-tenth the strength of the dye in the laboratory stockroom. You then dilute the stock solution made in the lab 4 times so that your final solution has a concentration of. You then take a few milliliters of the dye solution and insert it into the spectrophotometer and find the maximum absorbance of the dye.

For part 2 the lab provided an unknown liquid of dye where the type of dye was unknown. To measure the unknown you take a small amount of the dye and determine the maximum absorbance for the unknown. You then compare your known values to determine what the type of dye the unknown contained.

Part 1: Our group used the red and blue dye for our serial dilutions. The goal was to create the calibration curve graph for each dye. We used the dilution factor of to find our concentration of dye in order to do the curve. We did this by inserting 10mL of our previous dye into 90mL of undyed water. We found the concentrations of the blue dye at different concentrations to be: 1. The concentrations for the red dye were:. This shows there is a decrease in absorbance as the concentration of the dye increases.

project 2 food dye spectroscopy lab

Part 2: The unknown was measured to find a concentration of. This would indicate it is a combination of stock red solution, and. The objectives of the experiment were to find the calibration curve and be able to find the identity of an unknown dye identity. The only major source of error present could have been the systematic error present in the tools used as they are only precise to a certain decimal.

project 2 food dye spectroscopy lab

In this experiment, E. King and R.

Analysis of Food Dyes

Garner tested several reagents to determine in order to see what was the most efficient in determine the colorimetric values of blood glucose levels. With this being published inthis was significant because supplies for testing blood glucose levels would be limited, and the current method had the colors disappearing too fast to accurately determine the concentration of glucose in blood. This connects to our story as the more concentrated the glucose is, the more vivid the color is.In this experiment the goal is to determine the amount of dyes present in a powdered beverage in order to examine the allegation that the manufacturer is exceeding the allowable amount of the artificial food dyes in the drinks it produces.

The drink may contain more than one dye, and so the dyes must first be separated by column chomatography and then identified by colourimetric analysis. This is a qualitative analysis of the dyes. Once the dyes have been identified we can determine their concentration in the prepared drink using Beer's Law, another colourimetric technique. This is a quantitative analysis of the dyes. We start with a packet of drink that contains two different dyes. For example, a grape drink may contain a red and a blue dye that blend to result in a purple colour drink.

Our goal is to identify each of the dyes, and then, once identified, we can measure the amount of each. We express the amount as a concentration of the dye in the drink when it is prepared according to the package instructions.

Action: We dissolve a few grains of the solid drink in about a mL of water. We pour this mixture on a chromatographic column and wash it down with a lot of water. Result: The dyes leave the column at different times and we collect them in separate vials. Action: We take a spectrum of each dye, and also a spectrum of each similarly coloured standard dye available in the laboratory.

Result: Each dye has a unique spectral pattern. By matching the unknown dye to one of the standards we uncover its identity.

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Action: We prepare a set of dilutions of the standard dye its concentration is written on the bottle that matched our unknown. We measure the absorbance of each diluted solution at the analytical wavelength.

Result: We obtain a calibration plot of absorbance versus concentration at the analytical wavelength for the standard dye. We can use this plot to determine the concentration of the unknown once we measure its absorbance. Action: We prepare the drink according to package instructions and measure its absorbance at the analytical wavelength for the calibrated dye.

Result: We can read the concentration of the dye from the calibration plot. We can now calculate the amount of the dye in mg per L of the drink and determine the ADI value. The following pages contain tutors to assist you with identification of the dyes and the calculations required in some of the above steps.To get the best possible experience using our website, we recommend that you upgrade to latest version of this browser or install another web browser.

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Adsorption: Dyeing Fabrics with Kool-Aid

Would you drink black water? Clear Pepsi? How about using pink butter or green ketchup? Believe it or not, these products actually existed, and not that long ago either. But there is a reason these food fads did not last. Consumers prefer that the color of food matches its flavor. The link between color and taste is logical. Since oranges are orange, we expect orange-colored drinks to be orange-flavored. Red drinks should taste like cherries, and purple drinks should taste like grapes. If a food is multicolored, it could be moldy and should not be eaten, unless you are eating blue cheese—which gets its distinct flavor from mold!

An astonishing amount of the foods we eat is processed. These foods are altered from their natural states to make them safe, say, to remove harmful bacteria, or to make them appealing and to prolong their shelf life. Much of what we eat would not look appealing if it was not colored. Think of food coloring as cosmetics for your food. Without coloring, hot dogs would be gray. To avoid so much processed food, some have advocated using natural food coloring, whenever possible.Liquid food coloring is inexpensive, nontoxic and easy to find at the grocery store making it perfect for science experiments with young children.

Many food coloring experiments involve mixing colors and watching them travel through water or other liquids. When you are using food coloring for science experiments make sure that everyone is wearing old clothes and cover your work area with newspapers or plastic since food coloring can stain. You can use food coloring to demonstrate how water moves through the root system of a plant or flower.

To do this experiment you will need white carnations. Fill four or five cups with water and place five to 10 drops of food coloring in all but one cup. Leave plain water in the last cup as a control. Place one flower or stalk of celery in each cup and observe the flowers over the next three to four days. Watch and record what happens to the color of each flower. You can also do this experiment with celery, daisies or even white roses.

To watch colors mix in milk, get a plastic dinner plate with a rim and add enough whole or 2 percent milk to cover the bottom of the plate. Allow the milk to settle for five to 10 minutes.

Add one drop each of red, yellow, blue and green food coloring in the center of the plate. Keep them close together but not touching. Touch the tip of a cotton swab to the center of the milk without stirring the colors and watch what happens. Place a drop of dish soap on the clean end of the cotton swab and dip it in the milk again.

Watch what happens this time. Experiment with placing the cotton swab in different places and using different liquids to hold the food coloring. For another chance to observe the way molecules move, simultaneously put one drop of food coloring into a glass of very warm water and another in a glass of very hot water.

Watch how quickly food coloring spreads through each glass of water. You can even do this in a bathtub or small pool although the colors will be much more diluted.

Crafty experiments help children learn the properties of colors while making something attractive. Put drops of food coloring onto paper coffee filters and watch the colors spread and change. Once the colors have spread hang the filters up to dry. Cut them into flower shapes or into small pieces to make a collage.

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Dip a cotton string or pipe cleaner in the mixture leaving part of the string outside of the container. After 24 hours remove the string and lay it flat to dry.

The crystals will harden on the string as the water evaporates. Hang the string in the sun and watch it sparkle with colored light. Add drops of food coloring to ice cube trays to make red, yellow and blue ice cubes. Allow them to freeze until they are solid.

The Spectrophotometer: A demo and practice experiment

Fill three to five clear plastic cups halfway with very warm water. Place two differently colored ice cubes in one cup of hot water and watch what happens. As the ice cubes melt the colors will combine to make a new color. Try adding a different color of ice cube to a cup that already contains two melted cubes and watch what happens to the color of the water.Use paper chromatography to see which dyes are used in the coatings of your favorite colored candies.

Have you ever had a drop of water spoil your nice print-out from an inkjet printer? Once the water hits the paper, the ink starts to run. The water is absorbed into the fibers of the paper by capillary action. As the water travels through the paper, it picks up ink particles and carries them along. This same process that spoils a perfect print-out can also be put to good use. There is even a name for it: paper chromatography.

Chromatography is a group of techniques, including paper chromatography, that are used to separate the various components in a complex mixture or solution. In each chromatography apparatus there is generally a mobile phasewhich is a fluid that runs along the stationary phase, and a stationary phasethat stays stationary while the mobile phase moves through.

For example in paper chromatography, the mobile phase could be rubbing alcohol, while the stationary phase is the paper, or more precisely the water that is adsorbed to the paper. The mobile phase is also called the solvent. How does the chromatography setup separate the components in the solution? The components ideally move at different speeds as they travel through the stationary phase.

This is done by adjusting the mobile and stationary phases so that individual components of the mixture interact with both phases differently.

Properties such as solubilitypolarityelectrical chargeor other chemical properties usually determine how the components within a mixture are separated from each other.

In paper chromatography, different pigments can be separated out from a solution based on the same principles. A pigment that interacts more with the mobile phase, for example because it is more soluble in the solvent than another pigment will generally travel farther because it will be easier for it to dissolve in the mobile phase and be carried with the mobile phase along the stationary phase.

A pigment that is less soluble in the solvent, or interacts more with the stationary phase than the mobile phase, will generally travel a shorter distance. A homemade paper chromatography testing box is made from a tall box with a lid.

A dowel spanning the width of the box is placed near the top to allow a binder clip to hold a paper strip that has been marked by colored pigments. The paper strip is long enough to reach the bottom of the box where there is a small pool of solvent.

project 2 food dye spectroscopy lab

As the solvent is absorbed by the paper and moves upward it brings some of the colored pigment markings with it. In paper chromatography, you can see the components separate out on the chromatography paper and identify the components based on how far they travel.

To do this, we calculate the retention factor R f value of each component. The R f value is the ratio between how far a component travels and the distance the solvent mobile phase travels from a common starting point the origin. For example, if one of the sample components moves 2.

You can use R f values to identify different components as long as the solvent, temperature, pH, and type of paper remain the same. In Figure 2, the light blue shading represents the solvent and the dark blue spot is the colored solution sample.This project is based on an introductory adsorption laboratory experiment from Dr.

Polly R. Piergiovanni at Lafayette College. What happens when you put clothes into a dye bath? As expected, they come out colored. However, the intensity and degree of color can be very different, depending on the type of dye and fabric you use.

Analysis of Food Dyes

Not every dye works with every type of fiber. So how does the color stick to the clothes?

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First, the dye has to get in contact with the fiber and needs to get equally distributed into the fabric. In the second step, the dye has to be retained by the fiber surface. The adhesion of dye to the fiber surface is the most important step in dyeing, and is called adsorption.

During this process, the dye also called the adsorbate forms a film on the surface of the textile, or adsorbent. The interaction between the dye and the fiber depends on their chemical structure and can be driven by chemical adhesion chemisorptionwhich includes ionic or covalent bonding and the formation of hydrogen bonds, or physical adhesion physisorption including van der Waals' forces or electrostatic attractions.

Let us look into that in more detail using the materials for this experiment as an example. Your adsorbent will be wool fabric, which is a natural protein fiber with lots of amino groups -NH 2.

Due to its chemical structure, shown in Figure 1, Red 40 is classified as an acid dye. So what is the dyeing mechanism for wool and Kool-Aid? Acid dyes only work in an acidic environment and you will use vinegar to acidify your dyeing bath. The acid protonates which means it adds a proton to the amino groups of the wool fiber, so they become cationic positively charged.

Red 40, on the other hand, is anionic negatively charged in a solution. During dyeing, the Red 40 will adsorb onto the wool fiber by forming an ionic bond, as shown in Figure 2.

An acid added to wool allows the wool to gain a positive charge while Red 40 is negatively charged while in a solution. An ionic bond is formed between the Red 40 and wool. Knowing the chemistry of how a piece of cloth becomes dyed is very important to the textile industry.This project is based on an introductory adsorption laboratory experiment from Dr.

Polly R. Piergiovanni at Lafayette College. What happens when you put clothes into a dye bath? As expected, they come out colored. However, the intensity and degree of color can be very different, depending on the type of dye and fabric you use. Not every dye works with every type of fiber. So how does the color stick to the clothes? First, the dye has to get in contact with the fiber and needs to get equally distributed into the fabric. In the second step, the dye has to be retained by the fiber surface.

The adhesion of dye to the fiber surface is the most important step in dyeing, and is called adsorption. During this process, the dye also called the adsorbate forms a film on the surface of the textile, or adsorbent. The interaction between the dye and the fiber depends on their chemical structure and can be driven by chemical adhesion chemisorptionwhich includes ionic or covalent bonding and the formation of hydrogen bonds, or physical adhesion physisorption including van der Waals' forces or electrostatic attractions.

Let us look into that in more detail using the materials for this experiment as an example. Your adsorbent will be wool fabric, which is a natural protein fiber with lots of amino groups -NH 2. Due to its chemical structure, shown in Figure 1, Red 40 is classified as an acid dye.

So what is the dyeing mechanism for wool and Kool-Aid? Acid dyes only work in an acidic environment and you will use vinegar to acidify your dyeing bath. The acid protonates which means it adds a proton to the amino groups of the wool fiber, so they become cationic positively charged. Red 40, on the other hand, is anionic negatively charged in a solution.


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