Apera Instruments AI1113 pH Calibration Buffer Solution Kit (7.00, 4.00), 8 oz. Each. Apera pH calibration buffers are produced in an ISO 9001:2015 facility with ISO 17025:2017 accreditation using high-purity reagents, deionized water and certified analytical balances in a temperature controlled environment. Reported values are accurate to +/- 0.01 pH at 25°C and are traceable to NIST Standard Reference Materials (SRMs). MSDS documents are downloadable. Certificate of analysis can be achieved by request. All pH buffers have a 2-year expiration from manufacture for an unopened bottle. Show more @media (max-width: 768px) { div[style*="column-count:3"] { column-count:2 !important; } }@media (max-width: 480px) { div[style*="column-count:3"] { column-count:1 !important; } } @media (max-width: 768px) { div[style*="column-count:3"] { column-count:2 !important; } }@media (max-width: 480px) { div[style*="column-count:3"] { column-count:1 !important; } } @media (max-width: 768px) { div[style*="column-count:3"] { column-count:2 !important; } }@media (max-width: 480px) { div[style*="column-count:3"] { column-count:1 !important; } }