Chromatography

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Analytical Chemistry

Naturally dyed skeins
Red dyed yarn. By Madison60 (CC BY-SA 3.0)

Analytical chemistry plays a crucial role in various fields, including food science, environmental monitoring, pharmaceuticals, and forensics. It involves the identification, separation, and quantification of chemical substances. In the food industry, analytical chemistry techniques are essential for quality control, ensuring food safety, and complying with regulatory standards. 

Dactylopius coccus (Barlovento) 04 ies
Cochineal (Dactylopius coccus ) larvae on a cactus pad. By Frank Vincentz (CC BY-SA 3.0).

Natural dyes, like cochineal, create vibrant red colors used for centuries. Cochineal is a natural dye extracted from the dried bodies of an insect of the species Dactylopius coccus. This dye can be found in food and cosmetics, but the laborious nature of harvesting these insects lead to the usage of artificial chemicals for coloring instead.

Cochinel Zapotec nests
Commercial harvest of the cochineal using Zapotec nests. By Oscar Carrizosa (CC BY-SA 3.0)

The Food and Drug Administration (FDA) regulates color additives labeled as  Food, Drug, and Cosmetic (FD&C) dyes. Erythrosine, also known as FD&C Red Dye #3,  has been linked to potential health risks and banned from cosmetics since 1990. In January of 2025, the FDA finally ruled to ban this chemical in food due to the association of thyroid tumor induction in rats and some association with behavioral developmental issues in children. Enforcement of this ban poses a clear example of how analytical chemistry can be applied to ensure food safety.

Chromatography

Chromatography tank
Credit:  Theresa Knott [CC BY-SA 3.0 or GFDL]
Chromatography is a collective term for a set of analytical techniques used to separate mixtures. Chroma means color and graph means to write or draw. Paper chromatography is an analytical technique used to separate mixtures of chemicals (sometimes colored pigments) using a partitioning method. The paper in this method is called the stationary phase because it does not move and serves as a substrate or surface for the separation. Analytes (substances being analyzed) are separated from each other based on a differential affinity to a solvent. The solvent dissolves and carries the analytes along the matrix of the stationary phase. Since the solvent moves through a wicking action, it is called the mobile phase.

The distance that the analyte migrates along the paper related to the total distance that the solvent or mobile phase moves is called the Retention Factor or RF.

R_{F} = \frac{D_{A}}{D_{S}} = \frac{Migration Distance Of Analyte}{Migration Distance Of Solvent}
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