Most likely the measurement was sensitive to the proteins and that the average zeta potential was around -14mV. That's only an average value and will also be dependent on pH.

Note, that proteins exist in solution as permeable chains of molecules with fixed charge locations. This means that the concept of zeta potential doesn't actually apply. Also, proteins in aqueous solution are a type of hydrophilic colloid and the usual explanations of colloid stability do not apply either, since such colloids are thermodynamically stable.

Zeta potential is a physical property which is shown by any particle in suspension, humon urine also behave like colloidal electrolyte with more than 80 percent of H2O as a solvent and rest are proteins and very other particles ,

Research show that urine sample has zeta potential-58.1(+|-)1.0mv

Thanks, B. S. Yadav, for your answer. May I request you to please share any relevant research papers where the zeta potential of the human urine in the solution form turns out to be -58.1(+|-)1.0 mV, as mentioned? It would be really helpful.

Thanks,

Anu