Synthesis of Chelating Agent Free-Solid Phase Extractor (CAF-SPE) Based on New SiO2/Al2O3/SnO2 Ternary Oxide and Application for Online Preconcentration of Pb2+ Coupled with FAAS

A new online solid phase preconcentration method using the new SiO2/Al2O3/SnO2 ternary oxide (designated as SiAlSn) as chelating agent free-solid phase extractor (CAF-SPE) coupled to flame atomic absorption spectrometry (FAAS) for Pb2+ determination at trace levels in different kind of samples is proposed. The solid adsorbent has been characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron miscroscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence spectroscopy (XRF) and textural data. The method involves the preconcentration using time-based sampling of Pb2+ solution at pH 4.3 through 100.0 mg of packed adsorbed into a mini-column under flow rate of 4.0 mL min-1 during 5 min. The elution step was accomplished by using 1.0 mol L-1 HCl. A wide range of analytical curve (5.0-400.0 µg L-1), high enrichment factor (40.5), low consumption index (0.5 mL) and low limits of quantification and detection, 5.0 and 1.5 µg L-1, respectively, were obtained with the developed method. Practical application of method was tested on water samples, chocolate powder, Ginkgo biloba and sediment (certified reference material). On the basis of the results, the SiAlSn can be considered an effective adsorbent belonging to the class of CAF-SPE for Pb2+ determination from different matrices.

本研究提出一种新型在线固相预富集方法：以新型SiO₂/Al₂O₃/SnO₂三元氧化物（命名为SiAlSn）作为无螯合剂固相萃取剂（chelating agent free-solid phase extractor，CAF-SPE），结合火焰原子吸收光谱法（flame atomic absorption spectrometry，FAAS），实现不同样品基质中痕量Pb²+的定量检测。该固体吸附剂通过傅里叶变换红外光谱（Fourier transform infrared spectroscopy，FTIR）、扫描电子显微镜（scanning electron microscopy，SEM）、能量色散X射线能谱（energy dispersive X-ray spectroscopy，EDS）、X射线荧光光谱（X-ray fluorescence spectroscopy，XRF）及结构纹理表征数据完成了物性表征。本方法的预富集步骤为：在pH 4.3条件下，以定时进样方式将Pb²+溶液以4.0 mL·min⁻¹的流速通过装填有100.0 mg该吸附剂的微型固相萃取柱，富集时长为5分钟；洗脱步骤采用1.0 mol·L⁻¹的盐酸溶液完成。所建立的方法具备宽线性范围（5.0~400.0 μg·L⁻¹）、高富集因子（40.5）、低溶剂消耗量（0.5 mL）以及优异的检出性能，其定量限与检测限分别为5.0 μg·L⁻¹和1.5 μg·L⁻¹。该方法的实际应用效果通过对水样、巧克力粉、银杏叶及沉积物标准参考物质（certified reference material）的检测得到验证。综合实验结果表明，SiAlSn是一类高效的无螯合剂固相萃取吸附剂，可用于不同基质样品中Pb²+的定量检测。