OBJECTIVE  To establish a method for simultaneous determination of 6 indole metabolites in aquatic products using HPLC-MS/MS, and investigate the content of indole metabolites during the storage process of aquatic products.

METHODS After homogenization, the samples were extracted by 80% acetonitrile aqueous solution(containing 0.1% formic acid) and purified by HLB solid-phase extraction column. The chromatographic separation was performed on an Agilent EclipsePlus C₁₈ RRHD(2.1 mm×100 mm, 1.8 μm), using 0.1% formic acid aqueous solution and 0.1% formic acid acetonitrile solution as mobile phases with a programmed gradient. APCI ion source was used with multiple reaction monitoring mode. Indole-3-formaldehyde was quantified using internal standard method, while other metabolites were quantified using external standard method.

RESULTS The calibration curves of the 6 indole metabolites showed good linear correlation coefficient(>0.99) in the range of 10−1200 μg·L⁻¹. The limit of detection(LOD) was 2 μg·kg⁻¹ for indole, 3-indoleacetic acid, and 3-methylindole, with the limit of quantification(LOQ) of 5 μg·kg⁻¹. The LOD was 1 μg·kg⁻¹ for indole-3-formaldehyde, indole-4-formaldehyde, and indole-5-formaldehyde, with the LOQ of 2 μg·kg⁻¹. The average recovery rates of 6 indole metabolites were between 63.18% and 102.58% with RSDs between 1.5% and 10.2%. As the storage time of aquatic products increased, the types and contents of indole metabolites were increased.

CONCLUSION  This method is simplicity, accurately, and provides a new way for the detection of 6 indole metabolites in aquatic products.