Isotope Dilution – Where it works. Where it doesn’t work. Where we should expand its use.

Overcoming Legacy Obstacles with Innovative Approaches
Oral Presentation

Prepared by D. Thal
Environmental Standards, 8331 East Walker Springs Lane, Suite 402, Knoxville, TN, 37923, United States


Contact Information: dthal@envstd.com; 865-376-7590


ABSTRACT

Some analytical methods, frequently those developed for persistent, bioaccumulating and toxic compounds, are required to provide high performance with low quantitation limits in the presence of significant interferences. In addition to high-resolution instrumental techniques and multi-functional separation (cleanup) techniques, inherent correction for variation in recovery through the analytical process is often needed. This inherent correction is often achieved by introducing stable-isotope labeled internal standards at the beginning of the analytical process. If the isotopically labeled standard is an exact analog of the target analyte, this approach is termed “isotope dilution”.

The application of isotope dilution analytical strategies has been used for several regulatory and some sub-regulatory methods over recent years, and is widely acknowledged to be useful in improving method robustness. This presentation will provide reports of experience in which isotope dilution has been essential, will identify situations in which it has limited value or a high cost/benefit ratio, and will identify situations that beg for new applications of the technique. Also presented will be a set of considerations for evaluating the value and practicality of the approach. Finally, having applied this information, a set of “highly recommended” analytes will be presented for which the need for regulatory isotope dilution methods is clear.