Lab: Chromatography

 Because there is no chemical bonding in a mixture, the phases can be separated by mechanical means. In a heterogeneous mixture like a salad, the pieces can easily be picked out and separated. It is as simple as sifting through the salad and picking out all the tomatoes and radishes, for example. However, many mixtures contain particles that are too small, liquids, or too many particles to be separated manually. We must use more sophisticated methods to separate the mixture.

The main difference between a pigment and a dye is their solubility:

• Pigment: An insoluble substance that is finely ground and suspended in a medium (like paint or ink). Pigments do not dissolve but instead form a separate phase, making them more stable and resistant to fading.

• Dye: A soluble substance that dissolves in a solvent (like water or ethanol) and chemically bonds or adheres to a material (like fabric or paper). Dyes are more likely to fade over time due to light and washing.

In summary, pigments sit on the surface of a material, while dyes penetrate and bond with the material.

Explain the difference between a pigment and a dye.

• A pigment is an insoluble colorant that coats a surface, while a dye is a soluble colorant that bonds with materials at a molecular level.

What kind of mixture are inks (pigments or dyes) in non permanent markers? Determine the solvent and solutes in the ink pens you tested.

• Inks in non-permanent (overhead) markers are typically dye-based mixtures. They use dyes, which dissolve in the solvent, to allow for easy application and removal from non-porous surfaces like whiteboards.

• For overhead markers, the solvent is often water or a mild alcohol (like isopropanol), which evaporates quickly, making the ink dry on contact but erasable. The solutes include dyes (for color) and sometimes additives that improve ink flow and consistency.

What is paper chromatography? Explain why it is a useful technique to separate these types of mixtures.

• Paper chromatography is a technique used to separate and identify components in a mixture by dissolving them in a solvent and allowing them to move along a paper strip. It's useful for separating dye mixtures, like marker inks, because different dyes travel at different rates based on their solubility and interaction with the paper, allowing us to see and identify individual colors within complex mixtures.

"How do the properties of dyes in different ink types (e.g., non-permanent vs. permanent) influence their behavior in a chromatography experiment?"

• The differences in solubility, polarity, and chemical composition lead to distinct behaviors of non-permanent and permanent inks in chromatography, influencing their separation and visibility in the experiment.

• To separate a homogeneous mixture (solution) using the process of paper chromatography.

• To calculate the Rf value of primary colors of ink pigments.

Paper chromatography is an analytical chemistry technique for separating and identifying mixtures that are or can be colored, especially pigments.

1. Expo Vis-a-Vis Wet-Erase Markers

• These markers often use water-soluble dyes rather than pigments. Dyes are generally smaller molecules that dissolve well in the glycol- or water-based solvent, giving the ink a vibrant color that adheres well but can be removed with a wet cloth.

2. Expo Low-Odor Dry-Erase Markers

• These markers use alcohol-soluble dyes or pigments. The choice between dye and pigment depends on the specific formulation, but both are designed to be easily erasable once dry. Pigments are sometimes preferred because they provide a more opaque color, whereas dyes can be used to create intense, bright colors that are easily visible on a whiteboard.

Rank the component colors (magenta, cyan & yellow) of the inks from highest to the lowest Rf values.

For typical inks like magenta, cyan, and yellow:

• Cyan usually has the highest Rf value because it is often more soluble in the solvent and travels further up the chromatography paper.

• Magenta typically has a lower Rf value than cyan but higher than yellow, as it has moderate solubility.

• Yellow generally has the lowest Rf value because it often interacts more strongly with the paper and has lower solubility in the solvent.

How does the behavior of component colors (dyes) in ink vary in paper chromatography based on factors such as their solubility in the solvent (water) and their interaction with the chromatography paper?

In paper chromatography, the behavior of component colors (dyes) in ink can vary based on several factors, including their solubility in the solvent (water, in this case) and their interaction with the chromatography paper. Here’s a breakdown of how the component colors typically behave:

• Cyan: This dye tends to be highly soluble in water, which allows it to travel further up the chromatography paper. Its lower interaction with the paper means it moves quickly, resulting in a higher Rf value.

• Magenta: Magenta generally has moderate solubility. It will travel a shorter distance than cyan but further than yellow. This intermediate behavior reflects its moderate affinity for the paper and solvent.

• Yellow: Yellow dye usually exhibits lower solubility compared to cyan and may adhere more strongly to the cellulose fibers of the chromatography paper. As a result, it travels the least distance, leading to the lowest Rf value.

How do the magenta, cyan, and yellow dye components in ink behave in your paper chromatography experiment based on their solubility in water and their interaction with the chromatography paper? Compare their movement using terms like low (least), intermediate, and high (most) solubility or interaction relative to each other.

In a paper chromatography experiment using water as the solvent, the movement of the magenta, cyan, and yellow dye components depends on their solubility in water and their interaction with the chromatography paper (which is typically made of cellulose and is polar).

• • Cyan dye: Typically has high solubility in water and low interaction with the paper, so it moves the farthest up the paper.

  • Magenta dye: Generally has intermediate solubility in water and moderate interaction with the paper, meaning it moves up the paper but not as far as cyan.

  • Yellow dye: Usually has low solubility in water and high interaction with the paper, so it moves the least distance.

Thus, in ascending order of movement: yellow (least), magenta (intermediate), cyan (most).