DURACAL pH Buffer Solutions
A patented procedure guarantees precision for five years even with alkaline pH buffer solutions. The otherwise frequent calibration errors can be avoided. The commonly-used buffers pH 4.01, 7.00, 9.21 and 10.01 are tested and certified by a laboratory accredited by PTB for pH measurement (DKD-K-06901). They can be used as 'Certified Reference Materials' (CRM).