Method capabilities are not limited to crude oil matrix but apply to other complex organic matter and water samples with suitable extraction methods. Marquis et al. successfully featured 4-BNMA derivatization for quantifying and confirming the number of carboxylic groups in cells and tissues. As products of crude oil and gas exploration, naphthenic acids in produced water have raised concerns due to toxicity to aquatic environments, requiring detailed characterizations. Therefore, we aim toward employing the developed method to characterize water-soluble acids in produced water, giving more detailed molecular information about carboxylic acids and supporting petroleum chemistry studies.