The challenge of o-phenylphenol detection in coffee: How "OPP-conjugates" hide their presence in green and roasted samples

o-Phenylphenol (OPP) is not a commonly used pesticide in the coffee production chain. Although it has only been detected in roasted coffee, it is unlikely that OPP can be formed during roasting. Its acidic nature may lead to the formation of conjugates with natural matrix components. The objective of this study is to optimize an analytical method to discover how these conjugates may mask the presence of OPP in coffee. Sample extraction with hexane followed by basic hydrolysis and then a QuEChERS method allows the presence of OPP to be quanti-tatively detected via UPLC-MS/MS. The optimized method was applied to the same Arabica coffee (Brazil), and the quantification of comparable amounts of OPP was observed in both green and roasted samples (34.8 vs 32.2 mu g/kg). The optimized procedure detected twice the amount of OPP in roasted samples, compared to the QuEChERS method, suggesting that roasting causes the partial hydrolysis of OPP conjugates.