Identification of 3-hydroxykynurenine and xanthurenic acid and determination of 3-hydroxykynurenine transaminase activity using HPLC with electrochemical detection (HPLC-ED) are described using mosquito larval samples as testing materials. Results indicate that 3-hydroxykynurenine and xanthurenic acid in crude biological samples can be identified based on their electrochemical and chromatographic behaviors during HPLC-ED analysis. Xanthurenic acid is produced through transamination of 3-hydroxykynurenine, and identification of xanthurenic acid in the mosquito larval extract also leads to the detection of 3-hydroxykynurenine transaminase activity in this insect species.