As an important treatment method, sulfur fumigation plays an essential role in the production and preservation of traditional Chinese herbal medicines. Although there is strict regulation on the use of sulfur dioxide, the abuse of sulfur dioxide still occurred from time to time. And the public faces a high risk of exposure. Because of the poor precision and tedious preparation procedures of traditional recommended titration, the accurate and convenient determination of sulfur dioxide in Chinese herbal medicines is still a critical analytical task for medicines safety and the public health. In this study, an accurate, high-throughput, and convenient method for the absolute determination of SO₂ in Chinese herbal medicines based on triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) technique is developed. The study compared the quantitative ability for sulfur when the ICP-MS operated under traditional single quadrupole (QMS) mode and novel triple quadrupole (MS/MS) mode with three Reaction/Collision cell condition (no gas, helium, and oxygen). The result indicated that when the concentration of sulfate ranging from 0.5 to 100 mg · L⁻?, isotopic ³⁴S can be selected as quantitative ion either the ICP-MS operated under the QMS mode or MS/MS mode. The use of helium in the Reaction/Collision cell decreased the single intensity of background ions. Better than QMS mode, the MS/MS mode can effectively reduced background interference. But there are no significant differences about the linear range and limit of detection. However, when the ICP-MS operated under MS/MS mode and oxygen was used as reaction gas in the Reaction/Collision cell, the ICP-MS/MS provided an interference-free performance, the linear range and limit of detection improved significantly. Either ³²S or ³⁴S exhibits an excellent linearity (r > 0.999) over the concentration range of 0.02-100 mg · L⁻?, with a limit of detection of 5.48 and 9.76 µg · L⁻? for ³²S?⁶O₄²⁻ and ³⁴S?⁶O₄²⁻, respectively. The Chinese herbal medicines was treated using microwave digestion added 6 mL nitric acid and 2 mL hydrogen peroxide before analysis. The amount of nitric acid and hydrogen peroxide were optimized. The method was validated using Chinese herbal standard reference material GBW10020. The sample was treated and detected in six parallel, and the average concentrations obtained using the developed method (0.42% ± 0.01%) is in excellent agreement with the standard concentration (0.41%± 0.03%). The study demonstrates an accurate and convenient approach for the quantification of SO₂ in Chinese herbal medicines.
Drugs, Chinese Herbal Microwaves