The Endless Frontier of POP Analysis
Accurate determination of persistent organic pollutants has come a long way in twenty years, but we should not rest on our laurels: increased speed, improved economics and a reduced environmental footprint are important targets.
Juan Muñoz-Arnanz, Lourdes Ramos |
The analysis of dioxin-like persistent organic pollutants (POPs) is commonly perceived as a difficult process that involves several sequential treatments of a sample and a sophisticated final instrumental determination. The perception is correct: analysis of POPs can be complicated.
The main issues are (1) the need to accurately determine specific compounds at very low concentrations in the presence of other species that are present at much higher levels, and (2) the presence of potentially interfering compounds in the extracts. Interlaboratory exercises have proven that most labs provide satisfactory results for standard solution analyses. This might be expected, given the highly sensitive and selective instrumentation, the well-established analytical conditions to ensure proper analyte determination, and the strict application of quality assurance/quality control (QA/QC) criteria, including regular running of blank samples to keep potential interference under control.
Also, as might be expected, the situation changes when complex matrices are being analyzed, such as sediments, foodstuffs and biological fluids. While satisfactory results are consistently provided by well-equipped and experienced labs, discrepancies are often observed with less well-trained labs. These inconsistencies should galvanize lower-performing labs to implement appropriate QA/QC programs and validate their sample treatment methodologies as, with appropriate training, an adequate level of accuracy can be achieved.
Does this mean that the methodologies used in POP monitoring programs have reached maturity and that no further improvement is required? We would say no, they have not, and that further improvement is essential.
Today’s selectivity and sensitivity of instrumental analysis of POPs could have been barely imagined twenty years ago; this is not where improvements are needed. Instead, emphasis should be focused on speed – aiming to improve throughput and reduce analysis response times; economics – aiming to reduce the price per analysis both in terms of time and reagent consumption; and sustainability – aiming to dramatically reduce waste generation and the long-term environmental impact of analyses.
While some modifications might be suggested regarding the methodologies and techniques used for instrumental determination, the biggest gains could be made by improving protocols for sample extraction and purification.
The initial sample volume needed for many types of POP analyses could be significantly reduced without affecting the detectability of the investigated analytes. In the last two decades, researchers have proposed alternative extraction and enrichment techniques, and many conventional, that is, large-scale, methodologies have been replaced by more efficient, faster and greener analytical approaches that retain quality and efficiency. Multi-residual methods are valid approaches that enhance sample throughput and reduce reagent consumption without compromising data quality. New sample preparation techniques and approaches that enable miniaturization and solventless operation are often more productive and cost-effective than conventional sample treatment methodologies in use for routine POP analysis, while reducing occupational health risks and wastes. Apart from benefits derived from the fact that some processes exhibit slightly different behaviour at smaller scales, miniaturization is crucial when setting up (semi-)automated analytical protocols, speeding up sample preparation, decreasing reagent consumption and increasing sample throughput.
Changing a validated method to a multi-class, miniaturized or greener one is a challenge and requires effort and investment from laboratories, and from industry. In the case of POP analysis, where large quantities of reagents and toxic solvents are used in multi-step protocols, these analytical alternatives make sense not only from an economic standpoint, but also from an environmental point of view.
Dioxin Madrid 2014, the 34th International Symposium on Halogenated Persistent Organic Pollutants, runs Aug 31–Sep 5 (www.dioxin2014.org)