Objective In the context of increasingly stringent international regulations on chemical residues in consumer products, the comprehensive monitoring of phenolic compounds in leather goods has become a critical aspect for ensuring product safety and quality assurance. Current standard analytical methods often exhibit limited coverage, particularly concerning alkyl-substituted phenols such as ethyl phenols and propyl phenols. To solve the insufficient coverage of ethyl phenols, propyl phenols, and other phenolic compounds in present standard methods for leather products, this study aimed to establish a gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of eight phenolic substances in leather goods, including o-methylphenol, p-methylphenol, 2,6-dimethylphenol, 2-ethylphenol, 2,4-dimethylphenol, 4-ethylphenol, 2,3-dimethylphenol and 4-propylphenol. The proposed method is intended to modify the detection system, improve the monitoring capability for multi-phenolic residues in leather products and provide reliable technical support for product quality control, safety assessment and the development of related standards.

Methods In this paper, first, the initial column temperature and programmed heating rate were optimized to achieve satisfactory separation and peak shape. Second, positive leather samples containing the eight target phenols were prepared, and their stability was investigated. Third, five solvents with different polarities, including methanol, ethanol, acetone, ethyl acetate and chloroform, were compared in order to select the optimal extraction solvent. Forth, the effects of ultrasonic extraction time (10, 20, 30, 40 and 50 min) and temperature (20, 30, 40 and 50 ℃) on the recovery rate were deeply studied to determine the best pretreatment conditions. Fifth, the linear range, detection limit, quantification limit, recovery rate and degree of precision for the resulting method were systematically evaluated. Finally, the method was applied to detect the actual samples to verify its accuracy and applicability.

Results Eight types of phenolic substances were separated using a HP-5MS capillary column (30 m×0.25 mm×0.25 μm). The optimal temperature program was as follows: the initial temperature was held at 60 ℃ for 2 min, and the temperature was increased to 210 ℃ at a heating rate of 15 ℃/min and held for 1 min, then the temperature was raised to 280 ℃ at a heating rate of 20 ℃/min and held for 1 min. Mass spectrometry detection was conducted in a selected ion monitoring (SIM) mode with high-purity helium as carrier gas (flow rate 1.0 mL/min), and quantification was performed using an external standard method. Positive samples showed good stability within 36 h. Ethanol demonstrated higher extraction efficiency and lower matrix interference among the tested solvents. Ultrasonic extraction of 40 min was identified as the optimal time, with no significant improvement observed with longer durations. Temperature variations between 20 ℃ and 50 ℃ had no notable effect on recovery rate, indicating good operational stability. Under the optimized conditions, the eight phenolic compounds showed good detection linearity in the concentration range of 0.04-2.00 mg/L, with correlation coefficients all above 0.997. The method detection limit was 0.2 mg/kg, and the quantification limit was 0.8 mg/kg. Average recovery rates at three spiked levels (0.8 mg/kg, 4.0 mg/kg and 20.0 mg/kg) ranged from 75.8% to 117.3%, with relative standard deviations (RSD) between 1.2% and 7.9% (n=6). In the analysis of 10 batches of commercially available leather samples, p-methylphenol was detected in three batches at concentrations of 0.8 mg/kg, 1.0 mg/kg and 2.1 mg/kg, respectively, while the other target compounds were not detected.

Conclusion An ultrasonic-assisted extraction combined with GC-MS method was successfully developed for the simultaneous determination of eight phenolic compounds in leather. This method is characterized by simple pretreatment, rapid analysis, wide linear range, high accuracy and precision, strong resistance to matrix interference, and good operational stability. It is suitable for routine detection, quality monitoring, and risk assessment of phenolic compounds in leather and related products, providing an effective analytical tool for quality and safety control in the leather industry.