A DANREF Certified Reference Material for Chromate in Cement
Two candidate reference materials for chromate in cement were produced in the DANREF network and certified in an interlaboratory study. Fifteen laboratories participated in the interlaboratory study and six different analytical methods were used. The certified values were estimated as the consensus mean of laboratory mean values (outliers excluded). Only results from laboratories using methods relying on chromate speciation were accepted. The certified values (±95% confidence limits) were 0.678 (±0.075) mg CrVI kg–1 dry cement for the low level and 6.04 (±0.28) mg CrVI kg–1 dry cement for the high level. Methods based on total chromium determination gave on average results that were 6.5% higher (both levels). However, the difference between speciation and non-speciation results was significant at the high concentration level only.