Merck, 1.99002.0001, Buffer solution

The potassium dihydrogen phosphate/disodium hydrogen phosphate certified buffer solution is gravimetrically prepared using high-quality reagents and water at a registered calibration laboratory. Its pH value of 7.00 at 25°C is measured using a combined glass electrode following a 5-point calibration method. The measurement is made following DIN 19268 using reference buffer solutions compliant to DIN 19266, NIST, IUPAC, Ph. Eur, and USP. The buffer’s pH value is strongly dependent on the temperature and therefore a constant temperature must be maintained during its use. Please visit ISO certificates and Site Quality Self-Assessments to access the current certificates of accreditation. Download your certificate at http://www.sigma-aldrich.com to view certified values, including uncertainty and expiry date.