The OECD 101 UV-VIS Absorption Spectra test is used to assess the ultraviolet-visible (UV-VIS) absorption spectrum of a chemical compound to determine the wavelengths at which the compounds may be susceptible to photodegradation. The study design follows the current OECD Test Guideline 101 entitled “UV-VIS Absorption Spectra (Spectrophotometric Method)” and is performed in accordance with Good Laboratory Practice regulations.

How the OECD 101 UV-VIS Absorption Spectra Test is Performed

As is suggested in the test title, to perform this test will require the use of a UV-VIS spectrophotometer. Test solutions are prepared by weighing test substance to a concentration which will result in at least one absorbance maximum that is in the range of 0.5 to 1.5 units. As such this will require a range finding step to optimize the test article preparation.

Once the preparation of test solutions has been established, the UV-VIS absorption spectra is generated and the Molar Extinction Coefficient (MEC) is determined in acidic, basic, and neutral media. The acid medium should have a pH less than 2 and is typically 0.1 N HCl. The basic medium should have a pH of at least 10 and is typically 0.1 N NaOH. The MEC value of the test article will be established and verified using methanol as it is the proposed solvent as per ICH guideline S10 Photosafety Evaluation of Pharmaceuticals. Cell path lengths are usually between 0.1 cm and 10 cm.

The reason for the different media is that different forms of test article are present depending on the environment that it is contained in.

The test is designed to be reproducible, use minimal amounts of the test substance, and provide results that can be compared to other acute toxicity tests.

If absorption is found in the OECD 101 test, additional testing (such as the OECD 432: In Vitro 3T3 NRU Phototoxicity Test) is typically required. Nucro-Technics has experience in conducting both of these tests at its facility and both of them are run in compliance with Good Laboratory Practice regulations.