Evaluation of Analytical Chemical Methods for Detection of Estrogens in the Environment

Evaluation of Analytical Chemical Methods for Detection of Estrogens in the Environment

Summary

This study presents some suggestions and recommendations related to the analysis of steroid estrogens (primarily E1, E2, EE2) in environmental matrices such as influent and effluent waste water, surface water, sludge, manure, and soil. An analytical chemical method consists of a number of individual steps; sampling, storage, sample preparation and analysis/detection. The storage of samples is important for the final result as the estrogen stability is limited in most environmental matrices, e.g., effluent waste water. Sample preparation is often very cumbersome and the quality of sample clean-up is important in the selection of analytical detection methods. Steroid estrogens are to some extent excreted as conjugates by both humans and animals. Deconjugation techniques have been developed that make it possible to detect the entire estrogen concentration level followed by GC-MS analysis. LC-MS based methods are also available for direct analysis of conjugates. Several analytical detection methods have been suggested in the literature for analysing estrogens in the environment. UV, GC-FID and HPLC are not generally recommended due to low sensitivity and reduced selectivity. GC or LC hyphenated with single MS (GC-MS or LC-MS) or the use of immunochemical techniques are the minimum necessary to provide sufficiently high quality results. But both single GC-MS and LC-MS can be used even for very complicated matrices if certain identified quality criteria are fulfilled (LOD = 0.3 -5 ng/L). The effective use of single MS therefore requires verification of the selectivity of the method following selected criteria. If single MS methods are applied without such additional criteria LODs will be at the level of 20 ng/L or more.

The more advanced methods; LC-MS-MS or GC-MS-MS are found most suitable because these techniques provide the highest sensitivity (lowest LOD or LOQ) (LOD = 0.1 ng/L) and selectivity. Methods with an LOD of less 0.1 ng/L estrogen are not available on a commercial level. Such methods need further research in sample preparation combined with the application of highly sensitive triple quadrupole instruments.

Immunochemical methods are also very sensitive (LOD = 0.05 – 850 ng/L) at least for analysing waste water and STP effluents, but the selectivity is poor compared with the triple quadrupole instruments. Highly polluted samples should generally be avoided when using immunochemical methods due to adsorption to binding sites. Immunochemical methods are subject to problems with low selectivity and false positive samples. Variability is also often a severe problem with this technique. Because of these limitations, immunochemical methods are not recommended as a stand-alone “analytical tool”. Immunochemical methods have the potential to provide useful data when used in connection with chemical analysis, but today such strategies are not developed and research is needed to develop an appropriate strategy combining immunochemical methods with LC-MS-MS or GC-MS-MS or single MS.

The next few years will no doubt see the general application of these advanced techniques, integrated into completely automated, on-line systems. These integrated systems will improve analytical performance (analyse traceability, reliability, and repeatability), increase sample throughput, and reduce operating costs and contamination risks. Further advances in the form of new extraction techniques, such as those based on the use, on-line or off-line, of molecular-imprinting materials and immunoaffinity cartridges, which are currently underdevelopment, can be expected in the near future. These advances promise to greatly simplify the detection and measurement of these important environmental pollutants in environmental matrices. The introduction of biosensors, most of which are still in the prototype phase, will provide another promising alternative to traditional methods for the field monitoring of estrogenic compounds.