A simultaneous extraction/derivatization strategy coupled with liquid chromatography–tandem mass spectrometry for the determination of free catecholamines in biological fluids

•ZrO2 and PITC were used for extraction and derivatization of CAs, respectively.•Simultaneous extraction/derivatization of CAs from urines was achieved.•Detection sensitivity and chromatographic separation of CAs were improved.•Urinary CAs of healthy people and pheochromocytoma patients were detected.•The method has advantages in terms of sensitivity, specificity and selectivity.