Aflatoxin B₁ (AFB₁) contamination in Scutellaria baicalensis poses a serious threat to the safety of traditional Chinese medicinal products. In this study, a sensitive and reliable ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for the quantitative determination of AFB₁ in Scutellaria baicalensis. Method optimization included selection of chromatographic columns, mobile phase composition, and mass spectrometric parameters. Sample pretreatment was also optimized to reduce matrix interference and enhance extraction efficiency. The method showed excellent linearity (R² > 0.999) in the range of 0.1–10.0 µg/L, with a limit of detection (LOD) of 0.03 µg/kg and a limit of quantification (LOQ) of 0.10 µg/kg. Precision and recovery studies demonstrated good repeatability and accuracy, with intra- and inter-day relative standard deviations (RSDs) below 5.2% and recoveries ranging from 88.7% to 103.4%. Application of the method to six commercial Scutellaria baicalensis samples revealed detectable AFB₁ in two samples, though all levels were below national safety limits. This method provides a robust tool for routine monitoring of AFB₁ in herbal medicines and supports the establishment of quality control systems for Scutellaria baicalensis.

Hydroxyl radicals (•OH) are key reactive species in sonochemical processes; however, their generation is strongly dependent on the operating parameters and solution composition. In this study, probe-ultrasonication-induced oxidizing response was evaluated using an iodometric method in a 0.4mol L⁻¹ KI background, where the measured response reflects the accumulated titratable iodine (I₃^-) signal and is therefore discussed as an apparent •OH yield rather than an instantaneous steady-state [•OH]. The effects of sonication time (5–35 min), ultrasonic power (60–300 W), duty cycle (20%–100%), and probe position (top/middle/bottom) were systematically investigated. The apparent •OH yield increased with time and power, reached a maximum at a duty cycle of 60%, and was highest when the probe was positioned at the center of the liquid column. The influence of solution composition was further evaluated by adding ethanol, acetic acid, NaOH, NaHCO₃, and NaCl to the KI background. Increasing the ethanol and NaOH concentrations generally decreased the apparent •OH yield, whereas acetic acid showed a biphasic response. NaHCO₃ decreased the apparent •OH yield in a concentration-dependent manner, and NaCl showed a non-monotonic concentration dependence. In phosphotungstic acid systems, the iodometric response increased with concentration at 10 min but the concentration dependence diminished at 30 min, and a no-ultrasound control showed a measurable baseline signal while ultrasound produced a stronger response. Hydrogen peroxide markedly enhanced the response at moderate concentration but reduced the apparent •OH yield at higher levels due to competing reactions, while a t-BuOH scavenger control reduced the signal to about 10% of that without t-BuOH, indicating predominantly •OH-driven response with minor non-specific contributions. These results provide practical guidance for regulating the accumulated oxidative response in probe-ultrasonic systems.