Traceability of the Calibration
All Hellma Analytics certified reference materials are prepared in accordance with NIST (National Institute of Standards and Technology, USA), the European Pharmacopeia, adn the US Pharmacopeia (USP). Liquid filters are filled under controlled conditions, then the cells are permanently sealed. Solid filters are carefully cleaned and mounted stress free into their holders. The manufacturing process of the filters is completed by certifying them individually.
The manufacturing of the calibration standards is accomplished through the use of high performance UV/Vis/NIR spectrophotometer. These instruments are used exclusively for calibration purposes and are checked for their accuracy at fixed intervals of time.
For calibration of the spectrophotometer which is used to calibrate the Hellma Analytics filters, among others, the following sets of primary standards from the “National Institute of Standards and Technology” (NIST, USA) are used:
- SRM 930e Neutral Density Glass Filter
- SRM 2034 Holmium Oxide Liquide Filter
Primary instrumental wavelength calibration is established using the emission lines from mercury and deuterium sources. Linearity is established using double aperture method.