In this study, the in-situ conversion of the synthesized Co-Al layered double hydroxide (Co-Al LDH) nanosheets to three dimensional hierarchical zeolitic imidazolate framework-67 (3D HZIF-67) was presented as a cost-effective, highly efficient, flexible and robust sorbent to carry out the microextraction process. In the first stage, the anodized aluminum foil was prepared electrochemically. Then, the Co-Al LDH precursor was constructed on the surface of the previously-prepared anodized Al foil applying in-situ formation approach. The procedure is followed by the conversion of the prepared Co-Al LDH film to 3D HZIF-67 film via a facile solvothermal method without adding cobalt salt. The in-situ prepared 3D HZIF-67-anodized Al was used for the thin film microextraction (TFME) of caffeine. The effective factors in TFME procedure were investigated and optimized through applying Central Composite Design (CCD). In the obtained optimal condition, the calibration curves for TFME-HPLC-UV of caffeine were linear in the range of 1–200 µg L⁻¹ with the coefficient of determination (r²) higher than 0.9915. The limits of detection were 0.33 and 0.38 µg L⁻¹, in water and urine matrices, respectively. Moreover, the enrichment factors (EFs) and absolute recoveries (%AR) were also calculated as 173–198 and 57.1%-65.3%, respectively. The inter-day relative standard deviations (RSDs) were evaluated as the method precision for 20 and 200 µg L⁻¹ of spiked sample and were between 4.9–6.1%. The repeatability of the preparation step was investigated as batch-to-batch reproducibility and it was found to be 4.9%; as a result, the reproducibility of the presented film was approved. Finally, the proposed method was utilized to determine caffeine (as the model analyte) from different types of real samples including urine, coffee, beverage (Pepsi) and shampoo. The obtained recoveries (higher than 88%) confirmed the capability of the method for real sample analysis.

在这项研究中，提出了一种合成的Co-Al层状双氢氧化物（Co-Al LDH）纳米片原位转化为三维分层沸石咪唑酯骨架67（3D HZIF-67）的方法，具有成本效益，高效，灵活而坚固的吸附剂来进行微萃取过程。在第一阶段，以电化学方式制备阳极氧化的铝箔。然后，使用原位形成方法在预先制备的阳极氧化铝箔的表面上构建Co-Al LDH前体。该过程之后，通过简便的溶剂热法将制备的Co-Al LDH膜转化为3D HZIF-67膜，而无需添加钴盐。原位制备的3D HZIF-67阳极氧化铝用于咖啡因的薄膜微萃取（TFME）。通过应用中央复合设计（CCD）对TFME程序中的有效因素进行了研究和优化。在获得的最佳条件下，咖啡因的TFME-HPLC-UV的校准曲线在1–200 µg范围内呈线性大号^{- 1}与决定系数（R ²）大于0.9915更高。检测限为0.33和0.38微克大号^{- 1}，在水和尿液矩阵，分别。此外，富集因子（EFs）和绝对回收率（％AR）也分别计算为173–198和57.1％-65.3％。在日间的相对标准偏差（RSD）的评价为20和200μg的方法精度大号^{- 1}加标样品的百分比在4.9–6.1％之间。研究了制备步骤的可重复性，以批次间的可重复性进行，发现为4.9％；结果，所展示的膜的再现性得到认可。最后，所提出的方法用于从不同类型的实际样品（包括尿液，咖啡，饮料（百事可乐）和洗发水）中测定咖啡因（作为模型分析物）。获得的回收率（高于88％）证实了该方法用于实际样品分析的能力。