磁性三维氮掺杂碳纳米材料对6种双酚类化合物的吸附性能及其在泡腾分散微萃取中的应用

Adsorption characteristics of six bisphenol compounds on magnetic three-dimensional nitrogen-doped carbon nanomaterials and their use in effervescent reaction-assisted dispersive microextraction

采用简单高温煅烧法成功制备了磁性钴镍基氮掺杂三维碳纳米管与石墨烯复合材料(CoNi@NGC),将其作为吸附剂用于水体中6种双酚类化合物(BPs)的吸附性能和机理研究。将CoNi@NGC复合纳米材料用作萃取介质,运用酸碱泡腾片的CO_(2)强力分散作用,开发了泡腾反应强化的分散固相微萃取前处理方法,结合高效液相色谱-荧光检测(HPLC-FLD)快速定量饮料中痕量BPs。采用扫描电镜、透射电镜、傅里叶红外光谱、氮气吸脱附、X射线光电子能谱和磁滞回线等技术手段对材料形貌结构进行表征,结果显示:该吸附剂成功实现氮元素的掺杂,且具有较大的比表面积(109.42 m^(2)/g)、丰富的孔径及较强的磁性(17.98 emu/g)。吸附剂投加量、pH、温度、时间等因子优化试验表明:当pH=7,在初始质量浓度为5 mg/L的BPs混合溶液中投加5 mg CoNi@NGC,298 K反应5 min,对双酚M(BPM)、双酚A(BPA)的吸附率分别高达99.01%和98.21%。作用90 min时对双酚Z(BPZ)、BPA、BPM的吸附率近100%。在吸附过程中,BPs与CoNi@NGC之间的整个吸附过程主要受氢键、静电作用和π-π共轭作用共同控制。整个吸附过程符合Freundlich吸附等温线模型和准二级动力学方程,吸附自发进行。进一步将CoNi@NGC作为萃取介质制备成磁性泡腾片,利用泡腾分散微萃取技术高效富集和提取6种盒装饮料中的BPs,优化了影响富集效果的泡腾片的存在与否、洗脱剂种类、洗脱时间、洗脱体积等关键因子,在最佳萃取条件下(pH=7,投加5 mg CoNi@NGC,2 mL丙酮洗脱6 min),结合HPLC-FLD,新开发的泡腾分散微萃取方法提供的检出限为0.06~0.20μg/L,定量限为0.20~0.66μg/L,日内和日间精密度分别为1.44%~4.76%和1.69%~5.36%,在实际样品中不同水平下的加标回收率为82.4%~103.7%,在桃汁中检测到BPA和双酚B(BPB)分别为2.09μg/L和1.37μg/L。再生试验表明该吸附材料至少可以重复使用5次以上,显著降低了分析的试验成本。与其他方法相比,该方法具有灵敏度高、萃取速度快、环境友好等优点,在常规食品污染监测中具有较强的应用价值。

Herein,we successfully prepared magnetic Co/Ni-based N-doped 3D carbon nanotubes and graphene nanocomposites(CoNi@NGC)using a simple high-temperature calcination method.The CoNi@NGC nanocomposites were used as adsorbents to study their adsorption performances and underlying kinetic mechanisms for six types of bisphenol compounds(BPs)in water.They were also used as extractants,and acid-base effervescent tablets were used to enhance extractant dispersion with the aid of vigorous CO_(2) bubbling.Thus,a novel pretreatment method was developed,denoted effervescent reaction-assisted dispersive solid-phase microextraction(ER-DSM),which was combined with high performance liquid chromatography-fluorescence detection(HPLC-FLD)to rapidly quantify trace-level BPs in several drinks.The morphology and structure of the CoNi@NGC adsorbent were characterized in detail using scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),N 2 adsorption and desorption(BET-BJH),X-ray photoelectron spectroscopy(XPS),and vibrating sample magnetometry(VSM).The CoNi@NGC nanocomposites were successfully doped with N and exhibited large specific surface areas(109.42 m^(2)/g),abundant pores,and strong magnetic properties(17.98 emu/g).Key parameters were rigorously optimized to maximize the adsorption performance of CoNi@NGC,including adsorbent dosage,solution pH,temperature,and time.Under the constant conditions of pH=7,5 mg of CoNi@NGC,initial BP concentrations of 5 mg/L,and 5 min of shaking at 298 K,the adsorption percentages of bisphenol M(BPM)and bisphenol A(BPA)reached respective maxima of 99.01%and 98.21%.Remarkably,those of bisphenol Z(BPZ),BPA,and BPM reached almost 100%after 90 min.The adsorption between the BPs and CoNi@NGC was mainly governed by hydrogen bonds,electrostatic interactions,and π-πconjugation.The entire adsorption process was consistent with Freundlich adsorption and a quasi-second-order kinetic equation,representing spontaneous adsorption.Via integration with HPLC-FLD,ER-DSM was used to rapidly extract and analyze trace-level BPs in six types of boxed drinks.Critical factors were optimized individually,including the type of eluent and elution time and volume,which influenced the enrichment effect.Under the optimized extraction conditions(pH=7,5 mg CoNi@NGC,elution with 2 mL acetone for 6 min),the limits of detection and quantification of the novel extraction method were 0.06-0.20 and 0.20-0.66μg/L,respectively.The intra-and inter-day precisions spanned the ranges 1.44%-4.76%and 1.69%-5.36%,respectively,and the recoveries in the actual samples were in the range 82.4%-103.7%.Moreover,the respective residual levels of BPA and BPB in peach juice samples were 2.09 and 1.37μg/L.Regeneration studies revealed that the CoNi@NGC adsorbent could be reused at least five times,which significantly reduced the cost of evaluation.In summary,compared to other methods,this method displays the advantages of a high sensitivity,rapid extraction,and environmental friendliness,thereby exhibiting considerable potential for use in conventional monitoring of trace-level BPs in food matrices.