功能化磁性吸附材料制备及其在食品重金属检测中的应用

以Fe3O4作为载体,L-半胱氨酸(含巯基)作为功能单体,设计合成一种针对重金属吸附的L-半胱氨酸功能化Fe3O4磁性材料,并通过透射电镜及X射线光电子能谱等手段对材料进行表征。表征结果显示,磁性Fe3O4微球被硅胶层包裹在内,形貌上呈现典型"核-壳"结构,材料表面S元素负载量达8.2%(硫原子百分比)。以该材料作为固相萃取的吸附剂,吸附等温方程符合Langmuir吸附模型,Cd2+和Cu2+的最大吸附容量分别为238.1 mg/g和227.3 mg/g。结合石墨炉原子吸收光谱法,构建基于食品中痕量Cd2+和Cu2+的检测方法。系统考察影响吸附效率的多个参数,包括吸附选择性、吸附液pH值、吸附时间等。在优化条件下,该方法对Cd2+和Cu2+检测的线性范围均为:0.2μg/L^5.0μg/L,相关系数R2>0.997 0,检出限分别为0.12、0.13μg/L。将该方法用于实际样品的检测,回收率为87.0%~94.0%,相对标准偏差小于6.0%。

Preparation and Application of Functionalized Magnetic Material in Quantification of Heavy Metal Ions in Foodstuffs

The typical L-cysteine functionalized magnetic material for enrichment of heavy metals was successfully synthesized and characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The results showed that Fe3O4 magnetic core was shelled by mesoporous silica,and the capacity of thiol group with strong affinity to various heavy metal ions was as high as 8.2 %(atomic conc.). Using the obtained L-cysteine functionalized magnetic nanoparticles as solid-phase extraction adsorbent,adsorption isotherms of Cd2+ and Cu2+ fitted well with Langmuir model,showing high adsorption capacity of 238.1 mg/g and 227.3 mg/g,respectively. Combining the graphite furnace atomic absorption spectrometry(GFAAS),a method for determination of Cd2+ and Cu2+ in foodstuffs was developed. The experimental parameters affecting the adsorption efficiency including adsorption selectivity,pH value of the sample solution and extraction time were investigated systematically. Under the optimal conditions,the linear range of the method was 0.2μg/L-5.0 μg/L with the detection limits as low as 0.12 μg/L and 0.13 μg/L. The proposed method was further successfully applied for the determination of these target ions in rice and shrimp,and the recoveries were obtained in the range of 87.0 %-94.0 % with RSD lower than 6.0 %.