How long is your ph probe lasting ?

[adam01]

My ph probe (MW101 based) is 12 mo old. It doesn't easily resolve pool water ph unless the probe is transferred from 10ph solution (vs 7ph). Mfg suggests checking probe and recommends new probe as lifetime is 12-14 mo.

My probe reads wort ph quite well... Wondering how much longer I should hold on to it.

(BTW, probe is calibrated at each days testing. Probe is used 16-20 times a year at temps of 20-30C.)

 

[ajdelange]

I'm about to replace an electrode that went a couple of months over four years and have one that just won't die after 6. With a modern electrode you should get a couple of years at least. If the mfg told you a year buy a different meter. It was my understanding that the electrode used on the MW101 was the same as on the MW102 which I understand is a decent meter. Mfg says only 1 yr??

 

[mabrungard]

The SE-220 probe is a gel-filled, double-junction probe that is common to both the MW-101 and 102 meters. I've had one in service for over 4 years now and I'm still not seeing any drift in the calibration. I'm not surprised that the mfr states that limited life span since that is conservative. But with appropriate storage, I think you can get much longer life with most probes.

I've confirmed that gel-filled probes are well suited for storing in 1M to 1.5M KCl storage solution and I'm pretty sure that is a reason why I'm still seeing life in my probe.

 

[ajdelange]

pH electrodes should be stored in what the manufacturer says you should store them in. This is generally a solution of the same composition as the material in the last stage of the reference cell. As most reference cells are single junction Ag/AgCl electrodes filled with saturated (3M) KCl that is what most electrodes should be stored in.

If the design is double junction the manufacturer will probably want you to store in whatever is in the outer chamber (the one that communicated with the sample). If the design is such that the storage solution does not contact the reference (or in some cases even the sense bulb) then there is more flexibility in what can be used but one should still follow the manufacturer's instructions.

 

[ajdelange]

It is probably worth mentioning that a modern pH meter will, as part of the calibration, report (and perhaps store with the date and time) the calibration parameters (slope and offset). The MW101 is an analog meter and so can't do that but you can still get the information. Set the gain and offset controls to 0 and read each buffer. Record the readings. Ideally the 7 buffer will read exactly 7 and the 4 buffer exactly 4. The 7 reading is a measure of offset and the difference a measure of slope. So if the meter reads 7.2 in 7 buffer but the 4 buffer reads 4.2 then you have a slope of 3 (100%) but an offset of 0.2. If you record and monitor slope and offset you will detect aging problems with electrodes early on. Slope should start close to 100% (∆pH = 3) and gradually decrease over time (years) to about 95% (∆pH = 2.85). Offset can wander about around ±0.2 - 0.3 pH.