The pH 4.01 buffer is available in a 1 litre bottle, one of the most commonly used buffer solutions. It is extremely stable and represents the mid-way point in the acid range of the pH scale - ideal for those requiring an accurate acid reading, particularly those working in water purification plants, the food industry, and wherever the pH is expected to be acidic.

Buffer solutions should be stored at 25◦C, away from direct sunlight for accurate readings.

To correctly maintain your meter/electrode, we highly recommend use of a Hanna cleaning solution, as well as a buffer, for maximum performance every time. pH4, along with pH7, can also be used as an emergency storage solution.

Hanna buffer solutions are prepared, ready-to-use, according to precise formulas and standardised in accordance with the National Institute of Standards and Technology (NIST) to ensure quality and accuracy. All solutions show a batch number, an expiry date, and the correlation table between pH and temperature. A certificate of analysis is available on request. All bottled solutions are sealed with an air tight, tamper-proof seal to prevent any Carbon Dioxide from entering and causing a change in the pH buffer value.