Hanna pH 4.01 Calibration Buffer Sachet (20 mL)

This is a single-use sachet of pH 4.01 calibration buffer, holding 20 mL of standard solution. It is used to calibrate a pH meter or probe at the acidic end of the scale, giving you a known reference point so your readings stay trustworthy. The buffer reads 4.01 pH at 25°C with an accuracy of ±0.01 pH, and it is NIST traceable.

Each sachet is sealed in light-blocking foil, which protects the solution from UV exposure that could shift its value. Because you open a fresh sachet each time, the buffer is as good as the day it was packed, with no worries about a half-used bottle going off or becoming contaminated. The lot number and expiry date are stamped on every sachet, and an unopened sachet is formulated to last 2 years from the date of manufacture. The solution contains no dyes, so there's nothing to stain the reference cell of your electrode, and the colour-coded label makes it easy to tell buffer values apart.

It suits hobbyists who calibrate occasionally rather than every week, and anyone who wants a compact option for testing away from the tank or on the road.

Specs: pH 4.01 at 25°C, accuracy ±0.01 pH, 20 mL, 1 sachet.