BHT

Yehye, Wageeh A., et al. European journal of medicinal chemistry, 2015, 101, 295-312.

Butylated hydroxytoluene (BHT) represents a hindered phenol with a di-tert-butyl group on its phenolic ring which functions as a highly effective primary antioxidant. BHT is the most popular antioxidant used as an additive in industrial applications. For example, in 1998, BHT was determined to act as an antioxidant in cosmetic formulations based on an industry report that showed that BHT was used in 1709 formulations. Historical data from 1984 showed that BHT was used at concentrations as high as 1%, while the amount used in industry in 1999 was between 0.0002% and 0.5%.
BHT is also widely used in combination with other antioxidants such as BHA, propyl gallate, and citric acid to stabilize oils and high-fat foods. In addition, BHT and BHA can be used as secondary antioxidants by regenerating α-TOH.
This research also presented a summary of critical parameters influencing the antioxidant behavior of macromolecular phenols. Antioxidant properties of macromolecular phenols are affected by parameters including bond dissociation energy (enthalpy change), hydrogen bonding effects and 2,4,6-substituents and others like CoAH and thioether groups, aromatic amines along with solubility and thiourea systems.

Ghosh, Chiranjit, et al. RSC Advances, 2020, 10(11), 6671-6677.

Butylated hydroxytoluene (BHT) is a stable antioxidant widely used in skin care products, but the toxicity risk of long-term exposure to BHT remains controversial. BHT is currently generally recognized as safe (GRSA) when used in small amounts, 0.0002%~0.5% in cosmetic formulations, and the daily intake limit of BHT in food should be limited to 0-0.125 mg kg-1. In this work, a portable GC-MS headspace needle trap method was developed for the rapid quantitative determination of butylated hydroxytoluene in cosmetics.
Determination method
This study introduced a novel method utilizing purge-and-trap technology with a headspace needle trap device (NTD), alongside a comparative solid-phase microextraction (SPME) technique, both integrated with portable gas chromatography (GC) and toroidal ion trap mass spectrometry (MS) for the rapid detection of BHT in cosmetics. The sample was heated to 60 °C for 30 minutes in a glass vial to enhance BHT partitioning into the headspace, where it was concentrated by the NTD.
To quantify BHT in the samples, a standard addition calibration approach was used. A six-point calibration curve demonstrated excellent linearity (R² = 0.98) across a dynamic concentration range of 1000-10,000 ng mL-1 BHT in the sample matrix. The NTD method estimated BHT concentration at approximately 5000 ng/0.1 g of body lotion, while the SPME method yielded a value of around 5500 ng/0.1 g. These findings suggest that the BHT levels determined by the NTD method closely aligned with those obtained through the standard SPME approach.