KBr powder is graded solely by purity standards that are relevant to infrared spectroscopy. We do not use such terms as 5 9s (99.999%) , 6 9s (99.9999%) as the means used to test material for such certifications, such as emission spectroscopy, do not detect the types of contaminants that produce absorption bands in an infrared spectrophotometer. In the industry, the highest specification for transmission optics is beam splitter grade material which is generally specified by FTIR spectrophotometer OEMs as material having absorption bands due to impurities of less than 1% measured at 4 wave resolution between 4400cm-1 and 450cm-1. The cut off for commercial grade KBr crystal optics at ICL is material having absorption bands due to impurities of less than 2% at 4 cm-1 resolution. Other manufacturers use a looser standard. SpectroGrade™ KBr powder is all made from crystal boules that are suitable for IR spectroscopy based upon ICL’s testing standards. FTIR Grade SpectroGrade™ KBr powder is made from KBr crystal boules that are not quite beam splitter grade material and is defined as material that does not have any absorbance peaks in excess of 1.5%. FTIR Premium SpectroGrade™ is the equivalent of beam splitter grade material, and it is made from a blend of KBr crystal boules in which peaks range from 0.9% to 1.1% . XL Ultrapure SpectroGrade™ is a blend of material from rare boules that exhibit absorbance bands under 0.8% and the impurity range goes down to 0.2%. Sample purity certificates as pdf files can be printed from this site.