New video! Calibrating Free Radical Sensors

[by Nikki Scafa]


When using a TBR Free Radical Analyzer, accurate measurements of an analyte requires an accurate calibration. The calibration of nitric oxide, hydrogen peroxide and hydrogen sulfide sensors is similar. WPI oxygen and glucose sensors require different methods which will not be discussed here.





Before we begin:

  • Make sure you have the following items.
  • Your sensor must be polarized for the appropriate length of time.
  • Your solutions are prepared as described in the manual. (NOTE: Here we will show an item checklist slide (below) before continuing the video.)
Nitric Oxide ISO-NOP 2 mm 0.1 M KI/ H2SO4 50 µM KNO2 12 hours
ISO-NOP007  7 mm 0.1 M CuCl2 100 µM SNAP ≥2 hours
ISO-NOP3005 30 mm hour
ISO-NOP3020 30 mm 1 hour
ISO-NOPF200 200 mm 8+ hours
ISO-NOPF100 100 mm 8+ hour 
ISO-NOPNM 30 mm 1 hour
Hydrogen Peroxide ISO-HPO-2 2 mm 0.1 M PBS 1 mM H2O2 4+ hours
ISO-HPO-100 100 mm ≥1 hours
Hydrogen Sulfide ISO-H2S-2 2 mm 0.1 M PBS 1 mM H2S 12+ hours
ISO-H2S-100 100 mm 4+ hours


This demonstration shows methods used at the WPI lab. We are using an ISO-HPO-100 hydrogen peroxide sensor.

  1. After the sensor has polarized, use a pipetter to inject an aliquot of the calibration solution. We started with 2 µL of 1 mM hydrogen peroxide. Then, allow 30 seconds while the LabTrax records the data. The data trace plateaus.  
  2. Then, inject twice the volume of the first aliquot and allow another 30 seconds until you see the data trace plateau again. 
  3. Continue doubling the injection volume for another three injections, allowing 30 seconds to pass between injections.
  4. When you are finished, you should a data trace with 5 distinct plateaus.
  5. Using the LabTrax software, Determine the distance between the baseline reading and the plateau reading for each aliquot. That is the distance between the two red lines, and the delta is shown in the upper right corner of the screen. Using these figures, create a calibration curve and determine the R2 value.
  6.  After performing this calibration, the sensor is ready for use.


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