What's CMIT/MIT? and what's CMIT/MIT used for ?

Basic concept of CMIT/MIT( isothiazolone biocide)

CMIT/MIT (isothiazolone biocide) is a powerful preservative composed of 2-methyl-4-isothiazolin-3-one (MIT) and 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), typically in a 3:1 ratio, stabilized by inorganic salts. Originally developed by Rohmand & Haas in the U.S., CMIT/MIT (isothiazolone biocide) is known for its strong, broad-spectrum antimicrobial activity.

It is widely used in cosmetics, shampoos, conditioners, and other personal care products to inhibit microbial growth. At concentrations as low as 150 ppm, it completely inhibits bacteria, and at 125 ppm, it effectively stops yeast and mold. CMIT/MIT (isothiazolone biocide) is free of heavy metals and offers excellent preservation with high efficiency and safety.

Thanks to its strong biological activity and penetration ability, CMIT/MIT (isothiazolone biocide) is also applied in detergents, paints, industrial water treatment, machine tool coolants, and more. It helps prevent fermentation, spoilage, and microbial contamination. As a non-oxidizing, eco-friendly biocide, CMIT/MIT (isothiazolone biocide) is considered one of the most cost-effective options for preserving products across various industries, including textiles, papermaking, oil refining, and wastewater treatment.

Nature of CMIT/MIT (Isothiazolinones)

Antibacterial mechanism of Isothiazolinones (CMIT/MIT)

Due to the NS bond in the molecule, CMIT/MIT( isothiazolone biocide) plays a bactericidal effect by breaking the bond between bacterial and algal proteins. After contacting with microorganisms, it can quickly inhibit its growth. This inhibition process is irreversible, resulting in microorganisms. cell death. Before cell death, the microorganisms treated with CMIT/MIT( isothiazolone biocide) can no longer synthesize enzymes and secrete adhesive biofilm substances. By penetrating the biofilm adhered to the surface of the cold water system equipment, the microorganisms under the biofilm can be destroyed. effective control. 

As an isothiazolinone derivative, the relationship between CMIT/MIT( isothiazolone biocide) and various fungi has been extensively studied. As a heterocyclic compound, its bactericidal mechanism is mainly non-oxidative bactericidal effect, relying on the active part of the heterocyclic ring to form hydrogen bonds with the bases of DNA in proteins in bacteria, and adsorb on the cells of bacteria, thereby destroying the structure of DNA in cells. It loses its ability to replicate, resulting in cell death. Morley JO et al. further proved this sterilization mechanism by studying the electronic structure characteristics.

Antibacterial properties of Isothiazolinones (CMIT/MIT)

The bactericidal properties of Isothiazolinones (CMIT/MIT) have broad spectrum, can kill algae, fungi, bacteria, and at the same time have a penetrating effect on mucus, so that the microorganisms treated by Kasson cannot synthesize enzymes and secrete substances with adhesion and biofilm formation before cell death, and the sterilization is more thorough. ; Kathon is also effective at low concentrations. Generally, when the effective concentration is 0.5 mg/L, the growth of bacteria can be well controlled, which is unmatched by other agents; It can achieve physical compatibility with chlorine, corrosion inhibitor, scale inhibitor and dispersant and most anionic, cationic and nonionic surfactants. ~16:1, the product has a synergistic and spectral bactericidal effect; CMIT/MIT( isothiazolone biocide) can effectively organize the formation of slime, which can easily pass through the surface of the slime, thereby effectively killing the microorganisms in the slime, when the When the agent is put into a cleaning system, it can effectively prevent the growth of the slime layer; it is harmless to the environment, and the agent degrades quickly in the aqueous solution. Environmental pollution; it has a wide range of application to pH value, and can maintain high stability even in alkaline systems. Generally, the pH value can be applied in the range of 5.5-9.5; low toxicity, long dosing interval, and due to its No surface activity, the agent does not produce foam during use.

Research on Stabilizers of Isothiazolinones (CMIT/MIT)

1. Inorganic stabilizer

Substances that can be used as inorganic stabilizers for CMIT/MIT( isothiazolone biocide) mainly include metal nitrites or nitrates and metal salt complexes. Among them, there are many reports on metal nitrite or nitrate stabilizers. The metal salt complex can increase the thermal stability of the CMIT/MIT( isothiazolone biocide) solution while maintaining its biological activity . When sodium cupric citrate is selected as the stabilizer, the sodium cupric citrate itself also has a killing effect.

2. Organic stabilizer

Organic stabilizers are further divided into carbonyl compounds, halogen-containing organic compounds and other organic stabilizers.

What’s application of Isothiazolinones (CMIT/MIT)?

1. Industrial Biocidal Application

CMIT/MIT (isothiazolone biocide) is a highly effective industrial fungicide. It demonstrates strong bactericidal activity against both Gram-positive and Gram-negative bacteria, particularly Streptococcus and yeasts.

Main industrial uses include:

• Cosmetics & personal care products

• Coatings and water-based polymers

• Metal cutting fluids

• Adhesives, inks, dyes, paraffin fluids

• Leather and wood preservation

• Water treatment systems (e.g. industrial circulating water, swimming pool disinfection)

• Pulp and paper production

In China, CMIT/MIT is primarily applied in industrial open-loop systems, air scrubbers, oilfield water injection, synthetic fiber oils, and breweries, and has led to many patents and industrialized production. Domestic products have reached international quality levels.

2. Use in Cosmetics

CMIT/MIT (isothiazolone biocide) is widely used as a preservative in cosmetics due to:

• Low toxicity

• Broad-spectrum antimicrobial efficacy

• Good compatibility with cosmetic ingredients

• Water solubility and ease of formulation

It can be directly added to shampoos, conditioners, facial cleansers, and other personal care items. Its common trade name in cosmetics is Kathon CG.

3. Marine Antifouling Agent

In the early 1990s, Rohm & Haas developed DCOI (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one), an isothiazolinone derivative sold as Sea-Nine 211.

• DCOI is recognized as an environmentally friendly marine antifouling agent

• It replaces organotin and cuprous oxide compounds

• Awarded the Presidential Green Chemistry Challenge Award (1996)
  and the Chemical Environment Excellence Award (1997)

• Accepted globally as a green antifouling solution

4. Other Applications

CMIT/MIT (isothiazolone biocide) is also used in:

• Photographic chemical sensitizers

• Indoor air fresheners

• Audio tape raw materials

• Plant growth regulators

What’s advantage of isothiazolinones (CMIT/MIT)?

Synthesis of isothiazolinones (CMIT/MIT)

There are three main steps in the synthesis of CMIT/MIT( isothiazolone biocide):

First, by reacting methyl acrylate with sodium bicarbonate and sodium polysulfide to generate dimethyl dithiodipropionate;

Subsequently, dimethyl dithiodipropionate reacts with methylamine to generate N,N’-dimethyldithiodipropionamide;

Finally, N,N’-dimethyldithiodipropionamide reacts with sulfuryl chloride in the presence of dichloroethane as a solvent to form a mixture of MIT and CMIT, namely CMIT/MIT( isothiazolone biocide).

High-quality water-colored isothiazolinone fungicides can be achieved by:

①Select high-purity amide (N,N’-dimethyldithiodipropionamide) to reduce the generation of nitrous amines;

②Add a halogenating agent reasonably, and control the cyclization temperature at 5 ~ 20 ℃;

③The filter cake is washed at the same time by the combination of centrifugation and suction filtration to reduce the residue of solvent, hydrochloric acid and amine impurities;

④The isothiazolinone hydrochloride after vacuum drying should be prepared into liquid storage in time;

⑤ When making magnesium nitrate protective solution, pay attention to pH value adjustment and long enough clarification time to precipitate and remove iron ions and heavy metal ions;

⑥ The pH adjuster should choose the varieties with low content of iron and other chromophoric metal ions, in which the iron can be removed by physical and chemical methods. 

use standard

1. The dosage of ordinary daily cosmetics is 0.2-0.3‰
2. The dosage of high-grade cosmetics is 0.3-0.5‰
3. The dosage of washing supplies is 0.5-1.0‰
4.  

Identification

Analytical Method for Identifying CMIT/MIT (Isothiazolone Biocide) Purity

To identify and analyze the purity of CMIT/MIT (isothiazolone biocide), commonly known as Kathon preservatives, the following analytical techniques and approaches are used:

1. Chromatographic Techniques

• High Performance Liquid Chromatography (HPLC)

• Gas Chromatography (GC)

These are the standard methods used to separate and identify the components in the preservative sample.

2. Vector Analysis via Millennium 2010 Software

To confirm whether the unknown sample contains CMIT (5-chloro-2-methyl-4-isothiazolin-3-one) and MIT (2-methyl-4-isothiazolin-3-one), the vector calculation method is applied using Millennium 2010 software. Here’s how it works:

• A full-wavelength scan is performed across each point in the chromatogram.

• The ultraviolet spectrum at each time point is treated as a vector in a multi-dimensional space.

• The angle between vectors—called the purity angle—is used to determine the purity of each chromatographic peak.

3. Interpretation of the Purity Angle

The Millennium 2101 chromatographic system and 996 software automatically perform the vector angle calculations across each wavelength, allowing for accurate purity analysis.

4. Spectral Database Matching

• Based on the spectral comparison principle, the sample is matched against a standard compound database.

• This allows accurate and reliable identification of CMIT/MIT preservatives, ensuring quality control in both research and production environments.

Summary

Using a combination of HPLC/GC analysis, vector-based spectral purity evaluation, and standard database matching, the identification and purity determination of CMIT/MIT (isothiazolone biocide) becomes efficient, quantitative, and trustworthy.

Security

CMIT/MIT( isothiazolone biocide) preservative is a second-class corrosive product . Pay attention to safety protection during operation and avoid contact with skin and mucous membranes . Once in contact, rinse with running water immediately and repeatedly.