Yellow 5 lake or FD&C Yellow No. 5 lake is a synthetic azo dye, nitrogen-based. It is also known as E102 in the European food coloring list.

The name describes the structure of the molecule.

• FD&C indicates that the color is approved by the United States Food and Drug Administration (FDA) for use in foods, drugs, and cosmetics.
• Yellow No. 5 refers to a particular yellow color, also known as Tartrazine, which is a synthetic dye derived from coal tar.
• Lake indicates that the color has been combined with a substance (often a calcium or aluminum salt) to make it water-insoluble, often used in products that are not meant to dissolve immediately in water.

Description of raw materials used in production. 

• The dye is typically derived from coal and produced using a series of chemical compounds and processes, including the use of aniline, a petroleum derivative.

Step-by-step summary of industrial production process.

• Preparation of Sulfanilic Acid. Aniline is transformed into sulfanilic acid through a sulfonation process.
• Creation of Diazonium Salt. The sulfanilic acid is converted into a diazonium salt through a diazotization reaction.
• Formation of Tartrazine. The diazonium salt is coupled with pyrosulfuric acid and subsequently transformed into Tartrazine through a coupling process.
• Isolation and Purification. The formed Tartrazine is isolated and purified.
• Salt Formation. The dye is converted into its salt form to enhance water solubility.

Form and color. FD&C Yellow No. 5 comes as a yellow powder and is water-soluble, creating a yellow-colored solution.

Commercial applications. 

Tartrazine is widely used in many food products, beverages, cosmetics, and drugs for its ability to create a bright yellow coloring.

The problem associated with azo dyes (monoazo or diazo) is photocatalytic degradation (1) leading to eventual oxidation and subsequent formation of impurities such as aromatic amines (2) some of which have carcinogenic activity.

References_____________________________________________________________________

(1) Li M, He W, Liu Y, Wu H, Wamer WG, Lo YM, Yin JJ. FD&C Yellow No. 5 (tartrazine) degradation via reactive oxygen species triggered by TiO2 and Au/TiO2 nanoparticles exposed to simulated sunlight. J Agric Food Chem. 2014 Dec 10;62(49):12052-60. doi: 10.1021/jf5045052. Epub 2014 Nov 24. PMID: 25393426.

Abstract. When exposed to light, TiO2 nanoparticles (NPs) become photoactivated and create electron/hole pairs as well as reactive oxygen species (ROS). We examined the ROS production and degradation of a widely used azo dye, FD&C Yellow No. 5 (tartrazine), triggered by photoactivated TiO2 NPs. Degradation was found to follow pseudo-first order reaction kinetics where the rate constant increased with TiO2 NP concentration. Depositing Au on the surface of TiO2 largely enhanced electron transfer and ROS generation, which consequently accelerated dye degradation. Alkaline conditions promoted ROS generation and dye degradation. Results from electron spin resonance spin-trap spectroscopy suggested that at pH 7.4, both hydroxyl radical (•OH) and singlet oxygen ((1)O2) were responsible for dye discoloration, whereas at pH 5, the consumption of (1)O2 became dominant. Implications for dye degradation in foods and other consumer products that contain both TiO2 and FD&C Yellow No. 5 as ingredients are discussed.

(2) Belai N, White SR. Determination of Unsulfonated Aromatic Amines in FD&C Yellow No. 5 and FD&C Yellow No. 6 by Liquid Chromatography-Triple Quadrupole Mass Spectrometry. J AOAC Int. 2019 Mar 1;102(2):580-589. doi: 10.5740/jaoacint.18-0165. 

Abstract. Background: This paper describes a simple and sensitive ultra-HPLC-triple quadrupole MS (LC-MS/MS) method for the determination of six unsulfonated aromatic amines in the color additives FD&C Yellow No. 5 (Y5) and FD&C Yellow No. 6 (Y6). The six amines determined by this method are aniline (ANL), benzidine (BNZ), 4-aminobiphenyl (4ABP), 4-aminoazobenzene (4AAB), 2-aminobiphenyl (2ABP), and 4-aminobenzonitrile (4ABN). Objective: This method is intended for use in batch certification of the color additives by the U.S. Food and Drug Administration (FDA) to ensure that each lot meets published specifications for coloring foods, drugs, and cosmetics. Methods: A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure is used for extraction of the amines. Quantitative determination was performed in electrospray positive ionization and multiple-reaction monitoring modes. Results: Validation of the method demonstrated overall recovery of 101-115% and precision of 1.74-9.78% for all analytes. Excellent regression coefficients were obtained, with values >0.999. Conclusions: The validated method was successfully used for the analyses of 30 Y5 and Y6 samples and provided results that are consistent with results from the current method used by FDA, with greater sensitivity and low matrix effects. Highlights: The validation results demonstrate that the new LC-MS/MS method is applicable for use in routine batch certification.