from waste to health: application of mof modified walnut biochars for determination of twenty pesticides in wheat flour by ultra-high performance liquid chromatography-tandem mass spectrometry

Pesticides as an unavoidable part of crop cultivation have grown a great concern regarding food safety and wheat as one of the most important grains with high per capita consumption needs to be studied for possible contamination. in this research, walnut shell as high potential biomass has been used along with ni-metal organic framework (ni-mof) and thermally treated to obtain high efficient biochar with application in pesticide detection. the wheat specified pesticides with a good range of polarity (0.5-4.4 log p range) have been detected using the optimized walnut modified biochar as the sorbent and pipette tip-µ-solid phase extraction (pt-µ-spe) method as the extraction setup. modified biochars were characterized using regular methods and the role of ni-mof in the enhancement of obtained biochars was justified. in the following, the extraction setup parameters were optimized and the final method with 50%-ni-mof-walnut shell biochar as sorbent was evaluated for precision, accuracy, and other figures of merit. accordingly, the precision of the method was evaluated by rsd values obtained for intraday, interday, and synthesis procedure for all twenty pesticides in the wheat matrix. the limit of detection (lod) and quantification (loq) was also evaluated. consequently, the method was applied for the analysis of 29 wheat samples collected from all over the country and was able to find several pesticides which were compared individually with the maximum residue limit (mrl) defined by the european pesticide database. as a result, a map illustrating the wheat pesticide analysis was obtained and a risk assessment study has been performed on the acquired results. the risk assessment study demonstrated that target pesticides in analyzed wheat samples cannot cause non-carcinogenic harm to adults but might have an impact on children as more vulnerable consumers.