Merck, 1094361000, Buffer solution

The buffer solution (citric acid/sodium hydroxide) is gravimetrically prepared using high-quality reagents in high-purity water. It is quality controlled and qualified in an ISO/IEC 17025 accredited calibration lab. Its pH value of 5.00 at 20°C is qualified using a combined glass electrode following a 5-point calibration method, in accordance with DIN 19268, against certified primary reference standards as per DIN 19266, IUPAC, NIST, USP, and Ph. Eur. 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.