The pH 7.01 buffer in a 500ml bottle is the most commonly used buffer solutions. pH 7.01 is ideal for those requiring an accurate neutral reading, particularly those working in water purification plants, the food industry, aquatics, and Hydroponics, and wherever the pH is expected to be neutral. Latest Hanna portable and bench microprocessor instruments are calibrated with pH 7.01. Buffer solutions should be stored at 25 C, away from direct sunlight for accurate readings.