Isothiazolinones Quantification in Shampoo Matrices: A Matter of Method Optimization or Stability Driven by Interactions?

Mariana Tomás,Rita Palmeira De Oliveira,Ana Sofia Agonia,Lígia Borges,Ana Palmeira De Oliveira

doi:10.3390/cosmetics7010004

Mariana Tomás, Rita Palmeira De Oliveira + Show 3 more

Open Access

https://doi.org/10.3390/cosmetics7010004

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Journal: Cosmetics	Publication Date: Jan 1, 2020
Citations: 3	License type: CC BY 4.0

Affiliation: University of Beira Interior, University of Coimbra

Abstract

Methylisothiazolinone (MI) is one of the most used preservatives in shampoos and also one of the most effective. A preservative mixture known as Kathon™ CG is commercially available. It contains 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI) (3:1) and stabilizers. The aim of this study is to evaluate the influence of formulation factors in the quantification and stability of isothiazolinones in shampoos. Two shampoo bases containing Kathon™ CG as a preservative were prepared. Some ingredients that are at risk of interfering with the preservative stability were added to these formulations. The preservative was quantified by HPLC-DAD (High-performance liquid chromatography with a diode-array detector) after preparation of the formulation and after storage at room temperature and at 40 °C. The addition of magnesium silicate proved to be essential for the breakdown of the interaction between the matrix and the analytes in the extraction procedure. The content of CMI/MI decreased right after preparation indicating that immediate interactions between CMI/MI and the ingredients may have occurred after preparation resulting in a decrease in the preservative concentration. Detrimental interactions between the ingredients, regarding the stability of the isothiazolinones were detected immediately after preparation and over time resulting in the reduction of CMI/MI concentration in these cosmetic shampoos.

Highlights

Hair cosmetics, currently perceived as substances or mixtures that aim to clean, perfume, protect or keep the hair in good condition [1], represent a wide variety of products that are used with high frequency
Cosmetics 2020, 7, 4 elimination [3,4,5,6]. Based on their hydrophilic group, surfactants are classified as anionic, cationic, amphoteric and nonionic [3,4,6]
After 3 days the fortification of the same formulation with KathonTM CG presented a recovery percentage lower than 70%. These results suggest that there is an immediate interaction between ingredients that rapidly reduces the CMI/MI concentration

Summary

Introduction

Currently perceived as substances or mixtures that aim to clean, perfume, protect or keep the hair in good condition [1], represent a wide variety of products that are used with high frequency. Hair cleaning is the main purpose of shampoo as a cosmetic product, so surfactants are core ingredients of such products [3]. Surfactants are molecules presenting a lipophilic end that binds to small tallow droplets and a hydrophilic end, which allows the formation of micelles and have the ability to lower surface tension, destroy clusters and emulsify fats, in order to facilitate their. Cosmetics 2020, 7, 4 elimination [3,4,5,6] Based on their hydrophilic group, surfactants are classified as anionic (deep cleaning ability and high foaming capacity, e.g. sulfates), cationic (less cleaning capacity, but confer combing and smoothness properties to conditioners), amphoteric and nonionic (both mild surfactants mostly used in the formulation of baby shampoos) [3,4,6]

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