The chemical 4-amino-3-nitrophenol (4A3NP) is classified as an amino nitrophenol and is primarily utilized as an ingredient in hair dye colorants. In Korea and Europe, it is exclusively used in non-oxidative or oxidative hair dye formulations, with maximum allowable concentrations of 1% and 1.5%, respectively. Despite this widespread use, risk assessment of 4A3NP has not been completed due to the lack of proper dermal absorption data. Therefore, in this study, both the analytical method validation and in vitro dermal absorption study of 4A3NP were conducted following the guidelines provided by the Korea Ministry of Food and Drug Safety (MFDS). Before proceeding with the dermal absorption study, analytical methods were developed for the quantitation of 4A3NP through multiple reaction monitoring (MRM) via liquid chromatography-mass spectrometry (LC-MS) in various matrices, including swab wash (WASH), stratum corneum (SC), skin (SKIN, comprising the dermis and epidermis), and receptor fluid (RF). These developed methods demonstrated excellent linearity (R² = 0.9962–0.9993), accuracy (93.5–111.73%), and precision (1.7–14.46%) in accordance with the validation guidelines.The dermal absorption of 4A3NP was determined using Franz diffusion cells with mini-pig skin as the barrier. Under both non-oxidative and oxidative (6% hydrogen peroxide (H₂O₂): water, 1:1) hair dye conditions, 1% and 1.5% concentrations of 4A3NP were applied to the skin at a rate of 10 μL/cm², respectively. The total dermal absorption rates of 4A3NP under non-oxidative (1%) and oxidative (1.5%) conditions were determined to be 5.62 ± 2.19% (5.62 ± 2.19 μg/cm²) and 2.83 ± 1.48% (4.24 ± 2.21 μg/cm²), respectively.

Pyrogallol is an ingredient in hair dye. Its concentration in hair dye is managed at less than 2.0% in Korea. There have been no reports on the dermal absorption rate of pyrogallol. The two purposes of this study were to develop an analytical method and determine the dermal absorption rate of pyrogallol. An analytical method was developed and validated by high-performance liquid chromatography (HPLC) analysis of various matrices including swabs (SWAB), skin (SKIN, dermis + epidermis), stratum corneum (SC), and receptor fluid (RF). Linearity (r² = 0.9993–0.9998), accuracy (92.1–108.2%), and precision (0.5–9.5%) met the validation criteria in guidelines. A Franz diffusion cell was used to determine the dermal absorption of pyrogallol using the skin of mini pigs. Pyrogallol (2.0%) was applied to the skin (10 μL/cm²). For the actual hair dye conditions, the skin was wiped with a swab 30 min after application. Twenty-four hours later, it was wiped with a swab again and the SC was collected using tape stripping. All samples were extracted with water and analyzed. RF was recovered at 0, 1, 2, 4, 8, 12, and 24 h. The total dermal absorption rate of pyrogallol was determined to be 26.0 ± 3.9%.

Glyphosate is a non-selective herbicide. Although glyphosate is not acutely toxic, the intake of glyphosate-based herbicides has caused many accidents. Some studies have suggested that surfactants might be the cause. The purpose of this study was to compare the toxicokinetic (TK) properties of glyphosate according to different vehicles in rats. Glyphosate (1%) was dissolved in distilled water (DW), polyoxyethylene tallow amine (POEA), and Tween 20. After a single oral treatment of glyphosate (50 mg/kg), blood was collected at time intervals, and glyphosate concentrations in the target organ (liver and kidney) were determined 24 h after final blood collection. All samples were analyzed using LC-MS/MS. The TK parameters of glyphosate were similar in the DW and Tween 20 groups. However, there were significant differences in T_max and volume of distribution (V_d) between the DW and POEA group (p < 0.05). Glyphosate was absorbed about 10 times faster in POEA group rather than DW, and exhibited a higher distribution. However, other important TK parameters of T_1/2, AUC, and C_max were not statistically different among the different vehicle groups. Although glyphosate concentration in the liver was significantly higher in the POEA group than in the DW group, there was no significant difference in the kidney. These results indicate that the toxicokinetics of glyphosate are not significantly affected by POEA. It can be concluded that POEA toxicity itself can be attributed to the acute toxicity of glyphosate-containing products.