Tests and Assays

Interest has been expressed in the possibility of using biomarker assays as a part of risk assessment for regulatory purposes, and some workers have suggested tiered testing procedures that follow this approach (see, for example, Handy et al. 2003). It is to be hoped that regulatory schemes, such as that of REACH (see European Union 2003), will be sufficiently flexible to incorporate new assays and testing strategies as the science advances. 

Statistical analysis of results of biological assays and tests 5.3 (1997) European Pharmacopoeia 3rd Ed. Council of Europe, Strasbourg. 

PHYSIOLOGICAL ASSAYS AND TESTS OF EFFICACY CONCLUDING COMMENTS ACKNOWLEDGEMENTS REFERENCES... 

Although the assays and tests described constitute methods upon which the specifications of the Food Chemicals Codex depend, analysts are not prevented from applying alternative methods if they are satisfied that the procedures used will produce results of equal or greater accuracy. In the event of doubt or disagreement concerning a substance purported to comply with the requirements of this Codex, only the methods described herein are applicable and authoritative. 

Every FCC substance in commerce, when tested in accord with these assays and tests, meets all of the requirements in the monograph defining it. 

Analytical Samples In the description of assays and tests, the approximate quantity of the analytical sample to be used is usually indicated. The quantity actually used, however, should not deviate by more than 10% from that stated. 

Some substances must be dried before a sample is taken for an assay or test. When a Loss on Drying or Water test is specified, the undried substance may be used and the results calculated on the dried basis, provided that any moisture or other volatile matter in the undried sample does not interfere with the specified assay and test procedures. 

The word transfer, when used in describing assays and tests, means that the procedure should be carried out quantitatively. 

A residual blank titration may be stipulated in assays and tests involving a back titration in which a volume of a volumetric solution larger than is required to react with the sample is added, and the excess of this solution is then titrated with a second volumetric solution. Where a residual blank titration is specified or where the procedure involves such a titration, a blank is run as directed in the preceding paragraph. The volume of the titrant consumed in the back titration is then subtracted from the volume required for the blank. The difference between the two, equivalent to the actual volume consumed by the sample, is the corrected volume of the volumetric solution to be used in calculating the quantity of the substance being determined. 

Assay and test results are determined on the basis of comparison of the test sample with the reference standard that has been freed from or corrected for volatile residues or water content as instructed on the reference standard label. If a reference standard is required to be dried before use, transfer a sufficient amount to a clean, dry vessel. Do not use the original container as the drying vessel, and do not dry a reference standard repeatedly at temperatures above 25°. Where the titrimetric determination of water is required at the time a reference standard is to be used, proceed as directed in the Karl Fischer Titrimetric Method under Water Determination, Appendix IIB. 

International System of Units (SI), to the extent possible, is used in most specifications, assays, and tests in this Food Chemicals Codex. The SI metric units, and other units and abbreviations commonly employed, are as follows ... 

Note For use in assays and tests involving ultraviolet spectrophotometry, use ACS reagent-grade Ethyl Alcohol Suitable for Use in Ultraviolet Spectrophotometry. 

Already-established general assays and tests (e.g., titrimetric method of water determination, identification test) should also be validated to verify their accuracy (and absence of possible interference) when used for a new product or raw material. 

In considering the introduction of new test methods, it has been necessary for the USP to recognize the appropriateness of automating compendial assays and tests. The Committee of Revision prefers to adopt automatable procedures, especially for multiple-unit specimens such as those arising from dissolution or content uniformity requirements. Thus, since the publication of the USP XVIII in 1970, the General Notices to the... 

They should contain all data, assay and test results. 

Assay and test methods for each product should be established. This document should declare ... 

First-round screens based on random compounds or natural products are usually performed by testing one concentration of a new compound or natural product mixture. In some cases, the test is done in duplicate or triplicate, depending on factors such as space and time. Active compounds are then titrated for dose-response analysis. If a dose-response is observed, the active compounds are tested in the secondary assays, and tested for toxicity. Once a compound has proven active, not cytotoxic (if required), and dose-responsive, it can be ana-loged using combinatorial chemistry or medicinal chemistry methods. Small modifications in the side chains of active molecules will be produced, and these modified compounds tested in the assays. 

European Pharmacopoeia (1971) Statistical Analysis of Results of Biological Assays and Tests, vol. II, pp. 441-498. Paris Council of Europe, Maisonneuve S.A. 

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