Effects of carotenoid pigmentation in salmon on antibiotic extraction recovery, matrix effects and accuracy of quantification by ultrahigh performance liquid chromatography coupled to tandem mass spectrometry

Carotenoid pigmentation in salmon may interfere with the accuracy of antibiotic analysis with ultra-high pressure liquid chromatography coupled to tandem spectrometry (UPLC-MS/MS) by causing matrix effects or affecting the recovery of compounds during extraction. In the present study, we used both pigmented and non-pigmented salmon to understand the role pigments play on antibiotic analysis, and tested whether clean-up of the extract with dispersive solid phase extraction (dSPE) or hydrophilic-lipophilic balance (HLB) SPE clean-up reduces matrix effects. Thirty antibiotics and their respective class-specific surrogate standards were measured in Sockeye (pigmented), King (pigmented) and Ivory King (non-pigmented) salmon extracted using the QUEChERS method, or a modified QUEChERS method involving dSPE or HLB SPE clean-up (for Sockeye salmon only). Significant matrix effects and lower percent recoveries of spiked antibiotics were observed in pigmented versus non-pigmented salmon extracted with the QUEChERS method. Dispersive SPE clean-up did not improve extraction recoveries or matrix effects. However, SPE clean-up with HLB columns improved matrix effects for several antibiotics but reduced the percent recovery to < 30%. Across all types of salmon analyzed, the accuracy of quantitation was minimally impacted, likely due to similar behavior of the surrogate standards tagged to each antibiotic class during extraction. Our results demonstrate that carotenoids in salmon are associated with significant matrix effects and low extraction recoveries, but do not impact accuracy.