Comparative Evaluation Confirms Superior Performance of Metrohm Electrode for pH Measurement in Fuel Ethanol

Independent confirmation of the outstanding performance of Metrohm’s EtOH-Trode for pH measurement in fuel ethanol: in an evaluation of different combined glass electrodes by means of an inter-laboratory comparison, the Metrohm EtOH electrode with ground-joint diaphragm excelled by its outstanding precision.

While all the electrodes with aqueous KCl filling solution and single liquid junction presented equivalent results,
only the Metrohm electrode with its double liquid junction and one other electrode presented acceptable repeatability limit values.

The comparative evaluation was conducted by Mary Ane Gonçalves et. al. and published in Sensors and Actuators B 158 (2011), p. 327-332. The evaluation refers to the Metrohm EtOH-Trode as ‘electrode C’ and states: “Furthermore, only the C electrode showed reproducibility  limits as low as reported in the US Standard [ASTM 6423].
“Due to its remarkable precision, the C electrode presented a good compromise between trueness and precision, since  its pH results were only slightly higher than the results obtained with the A, B and D electrodes. This makes the C electrode a very good candidate for pH measurements of fuel ethanol.”

Because the pHe determination according to ASTM D 6423 and EN 15490 is time-controlled, it is essential that the sensor has a rapid response time. The Metrohm EtOH-Trode with a special membrane glass and the very precise fixed ground-joint diaphragm is particularly suitable for measuring the pHe values of biofuel.