Phosphate Buffer

Buffer Solution (pH 6.86) is a sterile, ready-to-use liquid reagent with a precisely known pH value of 6.86 at 25°C, specifically formulated for the calibration and quality control of pH meters, pH electrodes, and automated analyzers in clinical diagnostic and research laboratories . The solution is composed of potassium dihydrogen phosphate/di-sodium hydrogen phosphate (KH₂PO₄/Na₂HPO₄) in purified water, manufactured under ISO/IEC 17025 and ISO 17034 accreditation with traceability to NIST standard reference materials and PTB primary certified reference standards .

For the clinical laboratory scientist and medical technologist, Buffer Solution (pH 6.86) serves as the neutral calibration standard for two-point or three-point pH meter calibration (typically in conjunction with pH 4.00 and pH 9.18 buffers), ensuring accurate pH measurement of biological specimens including blood, urine, cerebrospinal fluid, and diagnostic reagents . The solution is measured using a combined glass electrode following a 5-point calibration method, compliant with DIN 19268, NIST, IUPAC, Ph. Eur, and USP standards . Each batch is accompanied by a detailed and batch-specific certificate of analysis (CoA) containing lot number, measured pH value (range 6.861 - 6.867), uncertainty (±0.02 pH), and expiration date .

The solution is classified as a Class I Medical Device (FDA Product Code JCC – General Purpose Reagent) and is 510(K) exempt, with GMP exempt status when not labeled as sterile . pH 6.86 buffer solution is available in various packaging formats including 30 mL sachets, 60 mL bottles, 100 mL bottles, 500 mL bottles, and 1 L bottles . Some manufacturers color-code the solution for easy identification (e.g., green or clear depending on the brand), and a pH/temperature table is printed on the label for accurate calibrations at different temperatures . The unopened shelf life is 2 years when stored at room temperature (15-25°C); once opened, the solution should be used within 90 days .

For the patient undergoing diagnostic testing for acid-base disturbances, metabolic disorders, or renal dysfunction, accurate pH measurement of biological fluids—verified through proper calibration with certified pH 6.86 buffer—ensures reliable test results that guide appropriate treatment decisions across clinical chemistry, blood gas analysis, urinalysis, and pharmaceutical quality control applications.