Materials necessary in the procedure for ORP measurement include chemical reagents, aqua regia, water, buffer standard salts, phthalate reference buffer solution, phosphate reference buffer solution, chromic acid cleaning solution, detergent, nitric acid, redox standard solution or ferrous-ferric reference solution, and redox reference quinhydrone solutions.

I need to use all of these materials, or one of these.

Or each materials use for individual reaction calibration?

Check it out from the library or download from http://www.astm.org

Dip the electrode in a Zobell's solution or a Light,s solution, adjust the reading to 228 if you use Zobell's; and 476 if you use Lights. Then you're done calibration!

We have technicians which can check out the unit for you and we also have the calibration solutions. Details at http://www.hydroterra.com.au

I like your response but correct only for ORP at 25ºC vs. saturated Ag/AgCl. If you use another solution the correction is shifted. This is the most common format. The platinum billet or wire needs to be cleaned of any sulphide or protein before use. Ensure that the measurement is made quickly on sampling if the redox is low and you expect oxygen to impact. If you are trying to measure a reduced solution must remember that it is being impacted by the atmosphere.

Hi and thanks for all. I need to reference article or book for this methods.

Needs for presentation about this.And I can’t find authorized Article or Another references.

Answer is correct but you are right, ASTM standards are not available for free.They key issue is to match the right procedure and values with the reagents you can have.

Be careful with both electrodes. First one is measurement (working), if it is platinum one, its response could modify in reducing media containing sulphur and mainly hydrogen sulphide. In this case, it is better to use gold electrode. Second is reference, two problems can take place: the measured value depends of the kind reference you use to be compare with others. Second problem is the contamination of reference electrode with species as sulphide, chloride, sulphate. Finally, it is better to use an individual reference electrode with salty bridge (potassium nitrate solution).

I highly recommend following the Equipment Test Procedure (Section 6.5.2) presented by Nordstrom and Wilde (TWRI Book 9, USGS) using Zobell solution. The method is easy to follow and Section 6.5.3 also provides procedures for sample measurement.

http://water.usgs.gov/owq/FieldManual/Chapter6/6.5_contents.html

I followed the Nordstrom and Wilde method for my master's project and it worked great! Additionally, I made an excel plot of the temperature dependent standard half-cell potentials (Table 6.5-2) for the 3.5M KClAg:AgCl electrode I used. The linear equation taken from this plot allowed me to easily correct Eref to the temperatures measured in the field.

Thanks for posting this information, and glad to hear this method was successful for you. ORP calibration, measurement, and calculation of Eh can be confusing. I don't believe the Standard Methods and ASTM procedures allow for correction of temperature differences between the sample and the calibration standard, and furthermore the ASTM method does not discuss the use of Zobell's solution which seems to be the most commonly used redox standard. The Norstrom and Wilde method is sound and easy to follow.

We have used Zobells´s solution and that works fine. However, there is need of an active redox couple, notably Fe2+/Fe3+. Readings with high redox potentials in the oxidating interval could be dubious.

The fact that you have indicated the value is an Eh measurement rather than a redox (EMF or ORP also used interchangeably) suggests not. The EMF reading that is made in mV is a function of the type of redox (ORP) probe used (more detailed discussions of this are easily found elsewhere). In order to correct the value to make it useful it must be corrected to a standard (or calculated) in order to be comparable to measurements made elsewhere using different equipment. The usual method is to correct to the standard hydrogen electrode (SHE) by means of one of two standard solutions which have established values. The solutions are the Lights's solution or Zobell's solutions (both named for the developers) which may be purchased or prepared in the lab. Once the correction is known it can generally be fed into most meters to allow you to read Eh directly.

Rather a quick and dirty explanation but as I say the information is readily available