Tools for Easier Compliance
The regulations for ultraviolet and visible spectroscopy were recently updated by the US and European pharmacopoeias. The revised US Pharmacopeia (USP) Chapter became mandatory on 1st December 2019. European Pharmacopoeia 10.0 (EP) Chapter 2.2.25 became mandatory on 1st January 2020. Both standards now require absorbance linearity to be qualified and that qualification measurements are made at parameter values that match or ‘bracket’ those used for analysis. This may well mean that a single reference for e.g. stray light will no longer suffice and explains why potassium chloride solution, for example, is no longer a universal stray light reference but is recommended for the far UV. It also means that it is no longer possible to specify universal ‘kits’ that can qualify instruments for all applications.
The Basic Qualification Kits described below, however, will meet the routine needs of many laboratories and can be supplemented with additional references if required. Starna CRM kits offer cost savings when compared to the purchase of individual references.
Basic Qualification Kits
The kits below will allow instrument qualification over the stated wavelength and absorbance ranges for compliance with EP 2.2.25 and USP . References are provided to qualify wavelength accuracy, absorbance accuracy and 3-point linearity, stray light and resolution/bandwidth.
The stray light references for USP compliance are for Chapter Method <857> B. Note that Potassium Chloride solution is included in all the basic kits as even if the instrument is not being used in the far UV, increasing stray light at this wavelength (200nm) is a sensitive indication of deterioration of the instrument optics.
These kits have been designed to qualify UV-visible spectrophotometers over the wavelength and absorbance ranges commonly used in pharmaceutical analysis. If your operating parameters fall outside these ranges, Starna has the world’s biggest range of spectroscopy CRMs and will be pleased to recommend additional or alternative references to meet individual requirements. For more information see Selecting References for Compliance - a User Guide or contact sales@starna.com for advice.
Basic Kit for EP 2.2.25 compliance
Catalogue number: RM-EP20
[Kit identity: RM-020610HLKCSIKISNTX]
| Reference | To qualify | Wavelength range |
| Holmium cell | Wavelength accuracy | 240 - 650 nm |
| Potassium dichromate 20, 60 & 100 mg/l & blank cell. | Absorbance accuracy and linearity, 0-1 A | 235 – 350 nm |
| Potassium chloride | Stray light, 200nm | 200 -370 nm |
| Sodium iodide | Stray light, 220 nm | 200 -370 nm |
| Potassium iodide | Stray light, 250 nm | 200 -370 nm |
| Sodium nitrite | Stray light, 340, 370 nm | 200 -370 nm |
| Toluene in hexane | Resolution (bandwidth), 265-270nm | 265-270 nm |
Basic kit for USP Chapter <857compliance>
Catalogue number RM-USP20
[Kit identity RM-02061060HLKCKIACSNTX]
| Reference | To qualify | Wavelength range |
| Holmium cell | Wavelength accuracy | 240 - 650 nm |
| Potassium dichromate 20, 60 & 100 mg/l & blank cell. | Absorbance accuracy and linearity, 0-1 A | 235 – 350 nm |
| Potassium dichromate 600 mg/l | Absorbance accuracy, 1 A | 430 nm |
| Potassium chloride | Stray light, 200nm | 240 -370 nm |
| Potassium iodide | Stray light, 250 nm | 240 -370 nm |
| Acetone | Stray light, 300 nm | 240 -370 nm |
| Sodium nitrite | Stray light, 340, 370 nm | 240 -370 nm |
| Toluene in hexane | Resolution (bandwidth), 265-270nm | 265-270 nm |
Basic kit for USP and EP compliance
Catalogue number RM-USPEP20
[Kit identity RM-02061060HLKCSIKIACSNTX]
| Reference | To qualify | Wavelength range |
| Holmium cell | Wavelength accuracy | 240 - 650 nm |
| Potassium dichromate 20, 60 & 100 mg/l & blank cell. | Absorbance accuracy and linearity, 0-1 A | 235 – 350 nm |
| Potassium dichromate 600 mg/l | Absorbance accuracy, 1 A (USP) | 430 nm |
| Potassium chloride | Stray light, 200nm (EP & USP) | 240 -370 nm |
| Sodium iodide | Stray light, 220 nm (EP) | 240 -370 nm |
| Potassium iodide | Stray light, 220 nm (USP), 250 nm (EP) | 240 -370 nm |
| Acetone | Stray light, 300 nm (USP) | 240 -370 nm |
| Sodium nitrite | Stray light, 340 nm (EP & USP), 370 nm (EP) | 240 -370 nm |
| Toluene in hexane | Resolution (bandwidth), 265-270nm | 265-270 nm |
Far UV extension kit - EP and USP compliance
Catalogue number RM-06A12A24ARE
| Reference | To qualify | Wavelength range |
| Cerium cell | Wavelength accuracy | 200 - 270 nm |
| Nicotinic acid 6, 12 & 24 mg/l | Absorbance accuracy and linearity, 0-1 A | 210 – 270 nm |
Visible Absorbance and Wavelength kit
Catalogue number RM-1N3N5DHG
| Reference | To qualify | Wavelength range |
| Holmium Filter | Wavelength accuracy | 240 - 640 nm |
| Neutral Density Filters, 0.25, 0.50 & 1.00A | Absorbance accuracy and linearity, 0-1 A | 440 – 635 nm |
Note: the Pharmacopoeias do not require stray light qualification above 400 nm.
Owners of earlier kits can easily upgrade to the new standards with additional or alternative references. In such cases, depending on your quality protocols, you may consider having the amended kit recalibrated at the same time as the new references to preserve the recalibration date.
Other Kits
Absorbance Linearity sets:
Potassium Dichromate linearity sets: a selection of solutions for qualifying UV absorbance linearity up to 3.5A (235 – 350 nm & 430nm)
Nicotinic Acid Linearity Set: Far UV absorbance linearity up to 1A (210 – 270 nm)
Starna Green Linearity Set: UV and visible absorbance linearity up to 1A (250 – 650 nm)
Neutral density filter sets: visible absorbance qualification up to 3A
NIST equivalent sets:
NIST has published specifications for absorbance filter Standard Reference Materials (SRMs). These filter sets are equivalent to these SRMs:
NIST equivalent Neutral Density sets: equivalent to NIST SRMs 930e, 1930 and 2930.
NIST equivalent Metal-on-Quartz set: equivalent to NIST SRM 2031a
Stray light filter sets:
Universal Stray Light reference set, Specified Wavelength method: USP and EP compliant
Stray Light reference set, Filter Ratio method: USP compliant, recommended for low stray light instruments