**4. Conclusions**

Analysis of isomeric pesticides requires the identification of product ions that are unique to each isomeric form. The use of HRAM mass spectrometry provided the molecular ion formula that led to the proposal of pathways and structure for these distinctive product ions for pebulate-vernolate, uniconazole-cyproconazole, and methiocarb-ethiofencarb. Thiobencarb and orbencarb can only be differentiated according to the relative intensities of the ions at *m/z* 89 and 100, but for sebuthylazine and terbuthylazine no differentiation could be established. The importance of identifying specific ions and determining their structures provides further support for elimination of false positives, and consequently, avoiding wrongful prosecution by providing further evidence for the analytical results in legal proceedings.

**Author Contributions:** Conceptualization, A.N. and Y.S.; Methodology, A.N. and Y.S.; Software, A.N.; Validation, A.N., Y.S. and S.J.L.; Investigation, Y.S. and S.J.L.; Writing-Original Draft Preparation, A.N.; Writing-Review & Editing, A.N., Y.S., and S.J.L.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Disclaimer:** Mention of brand or firm name does not constitute an endorsement by the US Department of Agriculture above others of a similar nature not mentioned.
