How to measure a trace amount like a few micro liter sample? Here is one way using HORIBA Compact pH meter LAQUAtwin (models B-711, B-712, B-713).

The flat sensor technology realizes the pH measurement of a few micro liter sample.

(The display resolution is selectable between 0.1 and 0.01 pH for B-712 and B-713(US only model))

What to prepare

1. Transparent sheet that does not absorb water (i.e. PET sheet used for clear file folder)

*Specially coated sheet which elutes acid or alkaline material should not be used.

2. Tweezer

3. Scissors 

Measuring method

・Please calibrate according to the instruction manual before the measurement.

1. Cut the transparent sheet into a shape that covers the glass electrode and liquid junction. Try to cut into the shape of the blue part seen on the sensor. The smaller the size, the more trace amount you can measure. 

2. Drop a sample on the center of the glass electrode. Using a micropipette may be easier.

?Click to enlarge the image

3. Place the sheet cutout over the sample, so that the sample connects the glass electrode and the liquid junction as per seen in the image below.

  • Do not press the glass electrode part too strongly.
?Click to enlarge the image

4. The measured value is displayed.

※Sample will be affected by the internal solution (potassium chloride), so please record the reading immediately (within 30 seconds).