NCL Technical Tips

Original Ammonia Probes

NOTE: NOT FOR HIGH-PERFORMANCE AMMONIA PROBES

1. After receiving a new Ammonia probe, condition it in accordance with the manufacturers 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 got 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. Allow AT LEAST two hours for the probe to stabilize after changing the membrane and/or filling solution. Overnight is better.
5. For Orion probes: After filling the outer body, hold it at an angle and tap gently to get rid of any air bubbles. 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!
6. For short term storage (one week or less): Store the probe (assembled) in 1000 ppm Ammonia Standard, WITHOUT and 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.
7. 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 with in 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.
8. Prepare your standards carefully using volumetric glassware, serial dilution's, and good lab technique. We will try to give specific directions on our next website update.
9. After preparing your standards, place the probe in the lowest valued standard, add the Sodium Hydroxide or Ammonia ISA buffer and set a timer for 4 minutes. Do not lock in the standard value until at least 4 minutes has elapsed. Repeat this procedure with your other standards. The standards are made with Ammonium Chloride. The probe measures ammonia. The Sodium Hydroxide or Ammonia ISA buffer converts the Ammonium Chloride to Ammonia, but the reaction IS NOT instantaneous. It takes 3-4 minutes. Many people have stated that they get a low slope when they calibrate, but if they re-calibrate using the same standards, the slope is within range. The reason is that they locked in before the reaction was completed. By the time they re-calibrated, the reaction in the standards was complete. However, you must complete the calibration within 20 minutes, as the ammonia gas will come off and decrease the standard's value.
10. If all of this fails, click the link that follows and run the inner-body check on your ammonia probe.

Inner Body Check

• DISTRIBUTOR FOR:
• ALCONOX
• BEL-ART
• COORS
• CORNING
• ERTCO
• DRIERITE
• HANNA
• HF SCIENTIFIC
• KIMBLE
• KONTES
• LABCONCO
• LAMOTTE
• METTLER
• MFS
• MILLIPORE
• NALGENE
• NASCO
• OHAUS
• ORION
• PRECISION
• SPECTRONICS
• THERMOLYNE
• WHATMAN
• WHEATON
• YSI
• WTW