The buffer solution (citric acid/sodium hydroxide/hydrogen chloride) 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 4.00 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.

It is used in analytical procedures for calibration, qualification, and monitoring of pH measuring instruments and as a control for testing other buffer solutions.

• Measured and qualified in an ISO/IEC 17025 and ISO 17034 accredited laboratory
• Traceable to SRMs from NIST and primary certified reference standards from PTB
• Ready-to-use solution available in a sealed bottle and an innovative Titripac^® packaging for positive environmental impact due to reduced waste generation
• Long-lasting with a shelf life of 3 years
• Accompanied with a batch-specific and detailed certificate of analysis (CoA) for an effective audit

CERTIPUR is a registered trademark of Merck KGaA, Darmstadt, Germany

Titripac is a registered trademark of Merck KGaA, Darmstadt, Germany