The HI4001-45 solution is for the conditioning and storage for the HI4101 ammonia gas sensing ion selective electrode (ISE). Measurement of ammonia in solutions is determined by a pH change of the internal thin film of electrolyte. This conditioning and storage solution is necessary to keep the glass pH sensing element hydrated in order to accurately determine ammonia concentrations. The HI4001-45 is a 500 mL bottle of conditioning and storage solution that ensures optimum measurement performance from the HI4101 ammonia ISE.