Technical Tips

Original Ammonia Probes (9512BN)

Note: Not for High-Performance Ammonia Probes

  1. After receiving a new Ammonia probe, condition it in accordance with the manufacturer’s instructions. Many people don’t think they have the time to do this, but they find the time to screw around with the probe for hours when they can’t make it work.
  2. When you get a new probe, you get new membranes and new filling solution. Throw the old membranes and filling solution away. If your old probe was shot, your membranes and filling solution are probably bad too. If you insist on using up the old supplies, the new supplies you received with this probe will become old supplies for the next probe. So you’re not really gaining anything, are you? Even though there is no expiration date listed, membranes develop pinholes and filling solution suffers from bacterial buildup.
  3. Change the membrane and filling solution every 2-4 weeks.
  4. Fill the outer body with exactly 2.5 ml of 951202 filling solution. Be careful not to overfill. If the filling solution squirts out the relief hole in the outer body, it can contaminate the standards, causing serious calibration problems.
  5. Allow AT LEAST TWO HOURS for the probe to stabilize after changing the membrane and/or filling solution.
  6. For Orion probes: After filling the outer body, hold it at a slight angle and tap gently to get rid of any air bubbles. Be careful not to tilt the probe to a horizontal position, because that may cause filling solution to run out of the relief hole. After assembling the probe, GENTLY pull on the cable at the top of the probe to get rid of trapped air bubbles. One major cause of unstable readings is trapped air bubbles at the bottom of the probe!
  7. For short-term storage (one week or less): Store the probe (assembled) in 1000 ppm Ammonia Standard, WITHOUT sodium hydroxide or ISA buffer. For long-term storage: Disassemble probe, drain filling solution, rinse inner and outer body with DI water, allow to air-dry, and reassemble dry.
  8. ALWAYS calibrate with AT LEAST two standards. The theoretical slope for ammonia probes is -59 mv/decade. In most cases, slopes between -54 and -60 mv are acceptable. With low range standards, such as 0.1 ppm, slopes as low as -50 mv are often observed. Most ISE meters manufactured within the last 10 years will automatically calculate and display the actual slope each time you perform a calibration of 2 or more points. There is no need to run a slope check with these meters.
  9. We sell ammonia standards already made up to common calibration values. If you are having problems, you may want to consider purchasing these ready-to-use standards, at least until you can resolve your ammonia testing problems. If you dilute your own standards from a concentrated standard, be sure to use serial dilutions for the entire series of standards. (Click here for instructions on making serial dilutions)
  10. After preparing your standards, rinse your probe off thoroughly with ammonia-free water. Then place the probe in your lowest standard. Add 1 ml of ISA buffer (NCL# A-15Y or O-951211) per 50 ml of standard. The probe should be at a 15-degree angle from vertical and the solution should be stirred with a stir bar at medium speed. Set a timer for 4 minutes. After 4 minutes have elapsed, lock in the calibration point upon a stable reading.
  11. Repeat this process for all other standards. Note: Most meters will display your slope after you successfully complete a calibration of 2 or more points.
  12. Add the same ISA buffer to your samples. Use the same probe technique as in the calibration above.

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