Patented DuraCal liquid pH buffer solutions provide a perfect complement for calibration of pH sensors. Hamilton pH calibration solutions offer stability of up to five years before buffer expiration. High buffering capacity provides rapid and stable calibration with accuracy up to +/- 0.01pH. Buffer solutions are tested against primary reference material from NIST and PTB. Each batch is also verified at an independent laboratory to ensure buffer solution accuracy. This top-down and bottom-up traceability approach ensures high accuracy and allows pH 4.01, 7.00, 9.21, and 10.01 buffer solutions to be classified as Certified Reference Material (CRM).