4-AminoPhenyl Phosphate or PAPP is an efficient substrate for Alcaline Phosphatase (ALP) and is precisely measured by electrochemistry.
See examples of the PAPP (ALP Substrate) applications in electrochemistry and ELISA asssays:
References
Berti F. et al.: Microfluidics-based electrochemical genosensor coupled to magnetic beads for hybridization detection, Talanta(2009); 77(3):971-8.;
Hoegger D. et al.: Disposable microfluidics ELISA for rapid determination of folic acid content in food products,Anal Bioanal Chem (2007) 387:267-275;
Rossier J. et al.: GRAVI™: Robotized Microfluidics for Fast and Automated Immunoassays in Low Volume, Journal of the Association for Laboratory Automation, (2008), 13(6), 322-329