Quantification of six types of cytokinins: Integration of an ultra-performance liquid chromatographic-electrospray tandem mass spectrometric method with antibody based immunoaffinity columns equally recognizing cytokinins in free base and nucleoside forms

•Developed tZR and iPR mAb with equal reactivity to tZR, tZ and iPR and iP, respectively.•tZR- and iPR-IAC with almost equal elution efficiencies to different forms of CTKs.•Six types of CTKs were measured by IACs coupled with UPLC-ESI-MS/MS.•Active forms CTKs notably decreased to increase the ration of IAA/CTKs.