From waste to health: Application of MOF modified walnut biochars for the determination of twenty pesticides in wheat flour by ultra-high performance liquid chromatography-tandem mass spectrometry

In this research, walnut shell along with a Ni-metal organic framework (Ni-MOF) was thermally treated to obtain a highly efficient biochar. A µ-solid phase extraction (µ-SPE) setup containing the optimized walnut modified biochar was implemented for the extraction of 20 wheat specified pesticides with a wide range of polarities. The modified biochars were characterized and the role of Ni-MOF on the porosity of the obtained biochars was investigated. After optimizing the extraction parameters, the 50 %-Ni-MOF-walnut shell biochar was selected. Accordingly, the precision for intra-day (2.4-25 %), inter-day (7-28.3 %) and synthesis procedure (4.1-26.7 %) was calculated. The limits of detection and quantification were in the range of 0.01-12.1 µg/L and 0.03-40.5 µg/L, respectively. This method was applied for the analysis of 29 wheat samples. The risk assessment study demonstrates that the contaminated wheat samples cannot cause non-carcinogenic harm to adults but might have an impact on children.