July 8, 2011
Determining Pollution Level Of A Medium Without Wasting Tools, Time Or Solvents Possible
Polycyclic aromatic hydrocarbons (PAH) are organic compounds that can be highly contaminant. They are found, amongst other places, in soils occupied by metallurgical or pharmaceutical industries and in waters polluted by ships' fuel. Chemist Dani Zuazagoitia has proposed simple techniques for analysing the impact of PAHs on a number of media, based on headspace solid phase microextraction (HS-SPME). He drew up the methodology, prepared it for the pertinent circumstances and applied it in the Basque province of Gipuzkoa. He defended the thesis at the University of the Basque Country (UPV/EHU), with the title Fase solidoko mikroerauzketan oinarritutako metodoen garapena hidrokarburo aromatiko poliziklikoen determinaziorako. Aplikazioa eta ebaluazioa ingurumen laginetan (Development of SPMEs for determining PAHs. Application and evaluation in environmental samples).
Mr Zuazagoitia has published a number of articles on his research, the latest being in the United States journal Soil & Sediment Contamination, and entitled Evaluation of soil contamination by polycyclic aromatic hydrocarbons in Gipuzkoa (Northern Spain).
Extraction without touching the sample
The HS-SPME procedure for the analysis of samples is a screening method; these analyses provide a rapid response (positive/negative) without wasting tools, time or solvents. With this procedure in concrete, a needle is inserted into the sample container top. This needle contains a fibre that has to be taken out of it on insertion, so that the substance to be analysed is absorbed from the headspace. This space is that between the sample and the cap and information can be obtained from there only in the case of volatile compounds such as PAHs. The procedure of extraction from the headspace enables conserving the fibre in optimum conditions. If it is inserted directly into the sample it can be spoilt due to the large molecules, but using HS-SPME, non-volatile and large molecule interference is avoided.
After extraction desorption should be proceeded with, in order to free the gases absorbed by the fibre and thus separate the substances. Mr Zuazagoitia opted for gas chromatography, by which the components can be separated with notable volatility at temperatures less than 350-400 degrees. Subsequently, the components were quantified using an FID ionisation detector.
Optimisation of three procedures
For his thesis Mr Zuazagoitia developed methods which, based on HS-SPME, determined various small and medium molecular weight PAHs simultaneously, considering the diversity of conditions that these methods have to comply with, depending on the matrix to analyse (water, earth, sediments, and so on). Likewise, given the numerous variables that condition the process, an experimental design that optimised the response of the method was opted for. Using the StatisticaÃ® programme, it is not necessary to carry out trials with each variable in order to ascertain their ups and downs beforehand.
Mr Zuazagoitia stated that, effectively, there exist rapid and simple methods and that can be undertaken with any laboratory analytical tools. Other characteristics of these methods involve having a rapid response (positive/negative) objective and being environmentally friendly, on not using organic solvents. The three procedures optimised in the thesis (water, earth, sediments) comply with these features.
In San Sebastián, Bergara and Pasaia
The researcher also took on the task of putting into practice methods for studying the pollution of water, earth and sediments in Gipuzkoa. According to the samples analysed, the concentrations of PAHs in the sea and river water in the territory are not relevant. However, there is a high level of contamination in leached waters, meaning that there is a high concentration of PAHs in soil these originate from. With the soil samples, Mr Zuazagoitia detected high levels of pollution in two zones of San Sebastian (the capital city of Gipuzkoa): in an area where a gas factory used to be located (in Morlans, Amara); and in a store for timber that was treated with creosote, a toxic substance (in Oriamendi). Finally, as regards sediments, PAHs were found in all the locations analysed and especially in the towns of Bergara (river Deba) and Pasaia (river Oiartzun).
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