CRMs for bromide

Two new 200 L polyethylene containers were cleaned by rinsing three times with tap water (that had been running for five minutes). Two other new 200 L polyethylene containers to be used for the collection of filtered samples were rinsed with tap water followed by rinsing with filtered (0.45 pm membrane filter) tap water. Tubes were soaked in Milli-Q water prior to use, for at least 24 h. 

The filters used for sample filtration were a Sartorius GF 0.2 pm Sartopure pre-filter cartridge followed by a Sartorius Sartobran PH membrane filter capsule (particle retention size 0.45 pm). The filters were autoclaved after used. Filters were used until clogging occurred. 

For the CRM 612 (high level), 200 L aerated groundwater was collected from Kege waterworks. Similar preparation procedures were used in comparison with CRM 611, with the exception that this material was not diluted with distilled water. 

The analytical methods used to verify the between-ampoule homogeneity were ETAAS (Al, Cd, Cu, Pb and Ni) and HGAAS (As). No inhomogeneities could be detected for any of these elements in both CRMs [17]. For bromide, determinations were carried out by ion chromatography the materials were both found to be homogenous [18]. 

The stability tests were performed over 52 weeks storage at +4°C and +20°C. A short-term stability study was also carried out at +40°C to test worst-case transport conditions. No instability could be detected at any of the conditions tested [17,18] in all the materials. 

---