Zur Analytik mikrobiocider Isothiazolone

Isothiazolone emissions from building products

Adding biocides to dispersion products is a well-known practice to control microbial deterioration. Isothiazolones are among the most commonly used preservatives, in particular a mixture of 2-methyl-2H-isothiazol-3-one (MIT) and 5-chloro-2-methyl-2H-isothiazol-3-one (CIT). In recent years, for health reasons, due to its strong sensitizing effect, CIT has been replaced by 1,2-benzisothiazol-3-one (BIT). Furthermore, numerous products are now available for interiors containing the fungicidal active substance 2-octyl-2H-isothiazol-3-one (OIT). So far nearly nothing is known of the emission behavior of BIT and OIT. An analytical method was developed for these two isothiazolones and interior products containing BIT respectively OIT have been investigated in an emission chamber and in test rooms. The chamber tests revealed maximum concentrations of 6.7 μg OIT/m3, 1.9 μg BIT/m3, and 187 μg MIT/m3. Concentrations obtained in the test rooms were at levels up to 1.4 μg OIT/m3 and 29 μg MIT/m3. A noticeable finding was the very slight subsidence of OIT and BIT levels over several weeks. While MIT outgassed quickly, OIT in particular showed low concentrations, but prolonged evaporation.

Kathon CG and cosmetic products

Kathon CG was determined in 156 of the most commonly used cosmetic products in Denmark. 42% of the cosmetic products were found to contain Kathon CG. Kathon CG was present in 48% of "rinse off" and 31% of "leave on" cosmetic products. The 3:1 ratio of chloromethyl isothiazolinone (CMI): methyl isothiazolinone (MI) in Kathon CG was found to be disturbed in 41% of Kathon CG preserved cosmetic products. The disturbed CMI/MI ratio was shown in 29% "rinse off" and 73% "leave on" cosmetic products. It is suggested that the chemical reaction of the ketone group of the isothizaolinones with other ingredients in cosmetic products may disturb the CMI/MI ratio of Kathon CG. The results of the study have been discussed in relation to the use of Kathon CG in cosmetic products as well as test material for allergic reaction.

[Preservatives based on methylisothiazolones in cosmetic products--theory and analysis]

Methyl isothiazolone formulations (Kathon CG) promoted as preservatives in the cosmetic field were investigated for their organic components by capillary gas chromatography/mass spectrometry. 2-methyl-3(2H)-isothiazolone and 5-chloro-2-methyl-3(2H)-isothiazolone were identified as effective major components and 4,5-dichloro-2-methyl-3(2H)-isothiazolone, 3-chloro-N-methyl-propionamide and dichloro-N-methyl-acetamide as minor components. Various methods like thin-layer chromatography with chemical and UV-detection, high-performance thin-layer chromatography using direct optical measurement, capillary gas chromatography with nitrogen selective thermionic detector, high-performance liquid chromatography with UV- resp. diode-array-UV-detector and UV-spectrometry were applied for detection and identification of the compounds. For quantitative determination it was necessary to obtain the corresponding purified isothiazolones as reference compounds. Commercial formulations were fractionated by reversed phase flash chromatography. Then the exact composition of the fractions obtained was determined by an absolute method, based on chemical reaction on a semi-micro scale. These solutions were used as reference for calibration. For quantitative determination of 2-methyl-3(2H)-isothiazolones reversed phase HPLC has proved to possess good reliability using the internal standard method (2-acetyl-5-chlorothiophen). Response factors and the relative calibration curves for this method were ascertained. A special technique based on extractive separation and purification by flash chromatography was developed for the isolation of 2-methyl-3(2H)-isothiazolone and 5-chloro-2-methyl-3(2H)-isothiazolone from cosmetic products. The average recovery rates and detection limits are given. The method was tested on several different commercial cosmetics. The samples contained between 5.5 and 39.4 mg/kg of methylisothiazolones.