A simple, rapid, and efficient method of dispersive micro solid phase extraction (D-μ-SPE) combined with UV-Vis spectrophotometry via ultrasound-assisted (UA) was applied for the determination and preconcentration of quercetin in extract of watercress (Nasturtium officinale), fruit juice and water samples. The sorbent in this method was synthesized by doping copper and sulfide into the tetragonal structure of SnO₂-nanoparticles (Cu- and S- @SnO₂-NPs) and subsequently loading it on activated carbon (AC). The D-μ-SPE parameters with direct effect on the extraction efficiency of the targeted analyte, such as sample pH, volume of eluent, sorbent mass and ultrasound time were optimized using central composite design method. Under optimized conditions, the calibration graph for quercetin was linear in the range of 20 to 4000 ng mL^-1; the limit of detection and quantitation were 4.35 and 14.97 ng mL^-1, respectively and the enrichment factor was 95.24. Application of this method to analyze spiked extract, fruit juice and water samples resulted in acceptable recovery values ranging from 90.3% to 97.28% with intra-day and inter-day relative standard deviation values lower than 6.0% in all cases. Among the equilibrium isotherms tested, Langmuir was found to be the best fitted model with maximum sorption capacity of 39.37 mg g^-1, suggesting a homogeneous mode of sorption for quercetin.

采用简便，快速，高效的分散微固相萃取（D-μ-SPE）结合超声辅助（UA）紫外可见分光光度法测定豆瓣菜（金莲花）提取物中槲皮素的含量并对其进行预浓缩），果汁和水样。该方法中的吸附剂是通过将铜和硫化物掺杂到SnO _2-纳米颗粒（Cu-和S- @SnO _2）的四方结构中而合成的-NPs），然后将其加载到活性炭（AC）上。使用中心复合设计方法优化了直接影响目标分析物萃取效率的D-μ-SPE参数，例如样品的pH值，洗脱液体积，吸附剂质量和超声时间。在最佳条件下，槲皮素的校准图在20到4000 ng mL ^-1范围内呈线性关系。检出限和定量限分别为4.35和14.97 ng mL ^-1，富集因子为95.24。应用此方法分析加标提取物，果汁和水样可得到可接受的回收值，范围从90.3％到97.28％，在所有情况下，日内和日间相对标准偏差值均低于6.0％。在测试的平衡等温线中，Langmuir被认为是最佳拟合模型，最大吸附容量为39.37 mg g ^-1，这表明槲皮素具有均一的吸附模式。