Merck, 1.99057.0500, Buffer solution

The yellow-colored di-sodium hydrogen phosphate/potassium dihydrogen phosphate buffer solution is gravimetrically prepared at a registered calibration laboratory with high-quality reagents and water. 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 pH is temperature dependent 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.