HORIBA LAQUAtwin pH-22 Pocket pH Meter Accuracy +- 0.01, Small Sample Amount min. 0.1mL for Water, Viscous Liquids, Solids, and Powder Samples

Although the manufacturer claims this device will measure as few as 50 to 100 ul per sample, they fail to say that it does so without much accuracy! That is, I tested the precision and repeatability of my newly-purchased LAQUAtwin pH-22 against a well-calibrated benchtop pH meter, using a commercial pH 7.00 calibration buffer and rinsing the LAQUAtwin with distilled water between trials. The LAQUAtwin gave inconsistent and erroneous readings (differing by about 0.5 pH units) when testing 100 ul samples. However, the LAQUAtwin gave excellent and repeatable readings when testing 400 ul. If you need to measure the pH accurately in <400 ul samples, this LAQUAtwin may not be useful for you.Ironically, even the LAQUAtwin tech rep I contacted said that I would have to use samples > 100 ul to get accurate readings.

This equipment comes to sit at 3 points, but it only comes with 2 solutions, 1 is missing and I can't find where to buy it, so I have not been able to calibrate my equipment.

Works well to test viscous foods. Needs to be reset a lot though.