Calibration Standards to Check the Photometric Accuracy
To check the photometric accuracy Hellma offers different kinds of standards: neutral density glass filters are very well suited for testing in the visible range, checking the photometric accuracy with potassium dichromate dissolved in sulphuric acid is the approved method for the UV region. Typically used standards have broad peaks and valleys. The following table shows the standards offered by Hellma and their compliance references:
| Checking for | Calibration Standard | Pharmacopeia | ASTM | ||
| EP | DAB | USP | |||
| Photometric Accuracy | Potassium Dichromate Liquid Filter | X | X | X | X |
| Neutral Density Solid Filter | X | X | |||
| Didymium Glass Solid Filter | |||||