Occurrence of Endocrine-disrupting Herbicides and Related Multiresidues in Natural Surface and Ground Waters from Aquifer: Control at Regulatory Levels by a Validated and Robust SPE-RP-HPLC-DAD Screening Approach

An reliable and robust analytical method combining off-line solid phase extraction (SPE) and reversed phase high performance liquid chromatography (HPLC) with diode array detection (DAD), has been developed for the simultaneous determination of six endocrine-disruptor herbicides, namely two parent S-triazines and their major dealkylated and hydroxylated degradation products such as atrazine (AT), simazine (SI), deisopropyl-atrazine (DIA), deethyl-atrazine (DEA), hydroxyl-atrazine (H-AT) and hydroxyl-simazine (H-SI), all of them with herbicide activity too. As optimal conditions were selected a Kromasil C18 column as stationary phase and a mixture of acetonitrile and phosphate buffer (pH 7.0) as mobile phase in a gradient elution mode and 215 nm as wavelength for optical detection. A previous SPE step with a polymeric cartridge (Bond-Elut ENV-1000 mg) was carried out to isolate and preconcentrate the sought analytes before chromatographic analysis providing thus a high enrichment factor of up to 3333. The optimized off-line SPE HPLC-DAD method was submitted to an extensive validation protocol obtaining among other parameters, very sensitive limits of quantification, between 81 and 100 ng L-1, which were from ten to thirty-fold lower than the allowed maximal amounts for natural surface waters (1 and 3 g L-1 as alert and alarm levels), according to current European Union directives. The reliability was assessed by an exhaustive robustness evaluation based on Plackett-Burman fractional factorial model followed by Youden and Steiner statistical treatment. Finally, the proposed method was successfully applied to the screening of herbicides in ground and natural surface water samples from different locations in the 23th aquifer (Albacete, Spain), with special focus to the hydroxylated degradation products, very common and whose detection has been scarcely addressed so far, despite their herbicide activity too, reason why they become an important matter of analysis.