Starna Certified Reference Materials are manufactured with extreme care under closely controlled conditions. Similar care should be exercised in their storage and use.

All Starna CRM’s carry a lifetime guarantee, provided they are used and stored correctly and recalibrated at intervals of not more than 2 years.

The certified values given on the Calibration Certificate are valid for a maximum period of two years, or shorter if required by the laboratory’s own protocols. The validity of certificates cannot be extended, and all references must be re-calibrated or re-certified after the expiry of the certificate. 


Storage and Care of Certified Reference Materials

  • Recommended handling procedures:
  • Only handle liquid references by either the ground glass faces or the cap and in the case of glass filters, by the sides of the anodised aluminium holder.
  • Replace the dust cover slides in the aluminium holder of glass filters after use.
  • Ensure consistency of cell orientation. Always orientate in the same way – ideally with the engraved face towards the detector.
  • Return the references to their storage container immediately after use.
  • Store in a clean, stable, dust-free environment, preferably between 15° and 30°C and with a relative humidity below 70%.


  • Do not touch the optical faces of cells or glass filters, except when cleaning liquid filled cells, see below.
  • Do not leave the references in an instrument measuring position for longer than necessary to generate the required data.
  • Do not leave the references exposed to direct sunlight, or any other continuum source of UV and/ or Visible radiation.
  • Do not clean glass filters, as this invalidates their certification.
  • Do not use lens cleaning tissue to clean the optical faces of a reference cell. These tissues are extremely thin and porous and will almost inevitably transfer surface contamination from glove or skin to the optical surface. See below for recommended cleaning procedures.
  • Do not expose to low temperatures. Freezing will cause permanent damage.

Cleaning procedure for liquid filled reference cells.

Note: This procedure does not apply to glass filters!

Other than by physical damage such as scratches etc., changes to the certified values are usually the result of contamination of the optical surfaces.

If cleaning becomes necessary, Starna recommend the following procedure:

  1. Blow any dust contamination off the optical surface at an angle with dry air or inert gas.

  2. Use a clean and dry microfibre cloth (Starna Optical Polishing Cloth, OPC, or similar) to remove other contamination. If this does not remove the surface contamination successfully then

  3. Wipe the optical faces with a Selvyt or lint-free cloth moistened with spectroscopy grade propan-2-ol. Then repeat instruction 2.

These procedures will usually restore the references back to either their original readings or well within the uncertainty budget. If this cannot be achieved they should be returned to Starna immediately for cleaning and/or recalibration.


All reference materials are certified and supplied in a useable condition. There is no warranty for fitness beyond receipt by the customer. Starna does, however offer a conditional Lifetime Guarantee on all Starna reference materials, unless otherwise stated, such that any reference material which moves outside its published uncertainty budget will be replaced free of charge. This guarantee is subject to the reference materials being re-certified at least every two years and to the references having been used and stored as prescribed in the Starna literature and have not been optically, thermally or physically abused.


Reference materials by their very nature need to be recertified at regular intervals to ensure the continued validity of their calibration values. As agreed with the accreditation authority (UKAS) the validity of Starna certificates expire after a period of TWO YEARS from the date of issue unless otherwise stated. Reference materials may be recalibrated at shorter intervals depending on the protocol under which they are being used, some periods being as short as three months.

The Starna calibration laboratory aims to re-certify and despatch reference materials within five working days from receipt. This minimises the time the customer is potentially without validation references. It is recommended that where possible laboratories have duplicate sets of references, re-calibrated in alternate years, thus ensuring continuous cover. On receipt by Starna Scientific the references are measured “As received”, before cleaning under the re-certification procedure. “As received” data is available on request.

The recalibration interval always assumes use, storage and care is as described in the Starna literature. In an environment where these above criteria cannot be met, and the user wishes to maintain the highest possible Quality Assurance (QA), it is suggested that the following procedure be adopted. First, a suitable protocol has to be established as only a statistical process can be used for determining the recertification interval. The certified reference material in question needs be recertified at least every twelve months for the first three years of use. Review of this data, in conjunction with the laboratory control limits, will enable an acceptable recertification interval to be established. This process should be incorporated in any formal control of the QA system, and any major changes in the laboratory environment should be evaluated with respect to their impact on the calibration of the certified reference materials.