In the present study, the applicability of ZIF-8/LDH/GO/PVDF as a sorbent for the thin film microextraction (TFME) method is introduced. The TFME method followed by high-performance liquid chromatography-ultraviolet detection (TFME-HPLC-UV) was applied for the rapid extraction and determination of caffeine (as a model analyte) in various caffeine beverages and urine samples. Parameters that affect the extraction of caffeine were optimized in two consecutive steps as follows: first, a Plackett–Burman Design (PBD) was utilized to screen the significant factors. Then, the screened factors were optimized by utilizing Box–Behnken Design (BBD). Under the optimized conditions (extraction time = 20 min, stirring rate = 665 rpm, salt effect = 20% w/v, 100 μL of methanol and desorption time = 2 min), the method showed good linearity in the ranges of 0.1–200 μg L⁻¹ and 0.2–200 μg L⁻¹ for caffeine in water and urine samples, respectively. The determined coefficients of determination (R²) were higher than 0.9968. Relative standard deviations (RSDs) for intra-day precision of caffeine at 10 μg L⁻¹ were 4.8% and 5.1% in water and urine samples, respectively. Finally, the method was successfully utilized for preconcentration and measurement of caffeine in various caffeine beverages and urine samples.

中文翻译：

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分子筛咪唑骨架-8在GO-PVDF膜上原位生长，作为咖啡因薄膜微萃取的吸附剂，然后通过高效液相色谱进行定量

在本研究中，介绍了ZIF-8 / LDH / GO / PVDF作为薄膜微萃取（TFME）方法的吸附剂的适用性。TFME方法随后是高效液相色谱-紫外检测（TFME-HPLC-UV），用于快速提取和测定各种咖啡因饮料和尿液样品中的咖啡因（作为模型分析物）。在以下两个连续步骤中优化了影响咖啡因提取的参数：首先，利用Plackett-Burman设计（PBD）筛选重要因素。然后，通过Box-Behnken设计（BBD）对筛选的因素进行优化。在最佳条件下（萃取时间= 20分钟，搅拌速度= 665 rpm，盐效应= 20％w / v，100μL甲醇和解吸时间= 2分钟），该方法在0范围内显示出良好的线性。水和尿液样品中咖啡因的含量分别为^-1和0.2–200μgL ^-1。所确定的确定系数（ R ²）高于0.9968。水和尿液样品中咖啡因在10μgL ^-1下的日内精度的相对标准偏差（RSD）分别为4.8％和5.1％。最后，该方法已成功用于各种咖啡因饮料和尿液样品中咖啡因的预浓缩和测量。