Simultaneous determination of four synthesized metabolites of mequindox in urine samples using ultrasound-assisted dispersive liquid-liquid microextraction combined with high-performance liquid chromatography

► A UADLLME was used as a pretreatment and extraction method of pig urine samples. ► Four synthesized metabolites of mequindox were target analytes. ► A fitting derivation data analysis method was proposed for the first time. ► EFs and LODs are comparable with other methods.