In this study, three batches of nano-titania functionalized covalent organic frameworks were acquired depending on different solvothermal reaction stages (24 h, 48 h and 72 h), which were named as single roll-up shaped nano-titania functionalized COFs (SSTF-COFs), double roll-up shaped nano-titania functionalized COFs (DSTF-COFs) and clover-shaped nano-titania functionalized covalent organic framework (CSTF-COFs), respectively. After comparing their extraction performances, the more efficient and stable CSTF-COFs were selected as sorbent for the dispersive solid phase extraction (dSPE) of eight target N-nitrosamines in drinking water, followed by the determination with liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). Owing to the introduction of hydroxy groups, CSTF-COFs showed high extraction efficiency for N-nitrosamines with a wide range of polarities through hydrogen bonding interaction, hydrophobic interaction and hydrophilic interaction. Under optimum conditions, the developed method provided relatively low limits of detection (0.13-2.45 ng/L) and satisfactory recoveries (88.6-105.5%), with relative standard deviations (RSDs) less than 8.3%. Therefore, with the assistance of CSTF-COFs, trace levels of N-nitrosamines were quantitatively and sensitively determined in 31 out of 460 bottled drinking water samples in a sensitive and convenient way.

中文翻译：

---

超声波辅助合成的三叶草形纳米二氧化钛官能化共价有机骨架，用于饮用水中N-亚硝胺的分散固相萃取。

在这项研究中，根据溶剂热反应的不同阶段（24小时，48小时和72小时），获得了三批纳米二氧化钛官能化的共价有机骨架，它们被称为单卷状纳米二氧化钛官能化的COF（SSTF- COF），双卷状纳米二氧化钛官能化的COF（DSTF-COF）和三叶草状纳米二氧化钛官能化的共价有机骨架（CSTF-COF）。比较它们的萃取性能后，选择了更高效和稳定的CSTF-COFs作为吸附剂，用于饮用水中八种目标N-亚硝胺的分散固相萃取（dSPE），然后通过液相色谱-串联四极杆质谱法（ LC-MS / MS）。由于引入了羟基，CSTF-COFs通过氢键相互作用，疏水相互作用和亲水相互作用，对具有宽范围极性的N-亚硝胺具有较高的萃取效率。在最佳条件下，开发的方法检出限相对较低（0.13-2.45 ng / L），回收率令人满意（88.6-105.5％），相对标准偏差（RSD）小于8.3％。因此，借助CSTF-COF，可以灵敏，方便的方式对460个瓶装饮用水样本中的31个进行了定量和灵敏的N-亚硝胺含量测定。6-105.5％），相对标准偏差（RSD）小于8.3％。因此，借助CSTF-COF，可以灵敏，方便的方式对460个瓶装饮用水样本中的31个进行了定量和灵敏的N-亚硝胺含量测定。6-105.5％），相对标准偏差（RSD）小于8.3％。因此，借助CSTF-COF，可以灵敏，方便的方式对460个瓶装饮用水样本中的31个进行了定量和灵敏的N-亚硝胺含量测定。