CI 42051 is a chemical compound is a synthetic dye, triphenylmethane. Triphenylmethane is a dark blue hydrocarbon. It is also known as Patent blue V, Acid blue 3. 

Raw Materials Typically Used in the Production of Patent Blue V (E131) and Their Functions

• Aniline. A primary ingredient used in the synthesis of many dyes, including Patent Blue V. It acts as a base molecule that is chemically modified to produce the dye.
• Sulfuric Acid. Often used in the dye-making process as a sulfonating agent to introduce sulfonic acid groups into the molecule, enhancing the dye's water solubility.
• Formaldehyde. Used in the chemical reaction to help in the polymerization process or as a stabilizing agent.
• Other Chemical Reagents. Various other reagents and catalysts may be involved in the synthesis process to facilitate the formation of the dye and to achieve the desired chemical structure.

Industrial Production Process

• Chemical Synthesis. Patent Blue V is produced through a complex chemical synthesis process, which involves the reaction of aniline with other chemicals, including sulfuric acid and formaldehyde, under controlled conditions.
• Purification. After synthesis, the dye is purified to remove impurities and ensure the quality of the color.
• Quality Control. Each batch of Patent Blue V undergoes quality testing to ensure its compliance with safety and purity standards.

Form and Color

Patent Blue V typically appears as a fine powder with an intense blue color

What it is used for and where

Food

It is labelled with the number E131 in the list of European colour additives.

Cosmetics

Blue dye.

Medical

Medical imaging in healthcare monitoring.

Safety

Two of EFSA’s Scientific Panels have both concluded that the colour Patent Blue V (E 131) is not a safety concern for people or animals when used as a food or feed additive at current levels of use. According to EU food and feed legislation, EFSA is required to operate under different regulatory frameworks with separate data requirements. 

From a genotoxic point of view, no effect has also been detected.

However, several studies have found cases of allergy to this dye (1).

Patent blue V studies

Molecular Formula: C₂₇H₃₁N₂O₇S₂Na (sodium salt)

CAS: 20262-76-4

EC Number: 243-654-4

Molecular Formula: C₂₇H₃₁N₂O₇S₂Ca (calcium salt)

CAS: 3536-49-0

Molecular Weight: 1159.422 g/mol

UNII: 8QE473DV1Z

Synonyms:

• Acid blue 3
• New Patent Blue A-CE Extra
• New Patent Blue Extra Pure A
• Acidal Carmine V
• E131
• Mitsui Acid Pure Blue VX
• Dai-ei Acid Pure Blue VX
• Alphazurine 2 G (C.I. 42051)
• Merantine Blue V
• Food Blue 5
• Solar Pure Blue VX
• Schultz No. 826
• Blue ZN 3
• Patent Blue V and L
• Carmine Blue V
• L-Blau 3 [German]
• C.I. Acid Blue 3
• C.I. Food Blue 5

References_____________________________________________________________________

(1) Vidya R, Athwal R, Huissoon AP, Baretto RL, Thirumala Krishna M. Diagnostic application of patent blue V in sentinel lymph node biopsy for breast cancer - Is it time for a change? Indian J Cancer. 2019 Jul-Sep;56(3):269-270. doi: 10.4103/ijc.IJC_139_18. PMID: 31389393.

Abstract. Sentinel lymph node biopsy (SLNB) was introduced in the 1990s, as a minimally invasive procedure for staging the axilla with less morbidity to the traditional axillary lymph node dissection and is now standard management of the axilla in the early breast cancer. SLNB using the combined technique of blue dye and radioisotope is currently the recommended method for lymphatic mapping, and studies have shown high identification rates (IR) (>95%) and low false-negative rates (FNR) 5-10%. However, there are several reports raising awareness regarding patent blue V dye-induced peri-operative anaphylaxis. The main aim of this article is to highlight the emergence of patent blue dye as a new allergen and present evidence regarding the utility of alternative safer methods of evaluation of early breast cancer without compromising IR.

Misir Šitum S, Korečić Zrinjščak I, Pečvarac M, Šoštar A, Žaja A, Tot T. Case report: Atypical anaphylactic reaction to Patent Blue V dye during breast cancer surgery. Front Oncol. 2022 Sep 16;12:979393. doi: 10.3389/fonc.2022.979393.

Costa D, Mendonça M, Lopes M, Fernandes AL, Nunes S, Müller S. Anafilaxia por corante azul patente V: relato de caso e revisão da literatura [Patent blue V dye anaphylaxis: a case report and literature review]. Braz J Anesthesiol. 2020 Nov-Dec;70(6):662-666. doi: 10.1016/j.bjan.2020.05.005.