Thermo Scientific® Orion™ ORP standards are now available to make tedious measurement simple. These solutions do not contain hazardous chemicals, are stable for up to a year (unopened) and can be used directly from the bottle with no mixing or diluting. Use as your relative mV standard and calibrate the offset of your sample. Designed for use with new Orion 91-79 Low Maintenance™ and 91-80 Refillable ORP Triode™ electrodes. Orion ORP standard is included in the new ASTM ORP method.