Diana L.D. Lima

Sorption-desorption behavior of atrazine on soils subjected to different organic long-term amendments.

Sorption of atrazine on soils subjected to three different organic amendments was measured using a batch equilibrium technique. A higher K(F) value (2.20 kg(-1)(mg L(-1))(-N)) was obtained for soil fertilized with compost, which had a higher organic matter (OM) content. A correlation between the K(FOC) values and the percentage of aromatic carbon in OM was observed. The highest K(FOC) value was obtained for the soil with the highest aromatic content. Higher aromatic content results in higher hydrophobicity of OM, and hydrophobic interactions play a key role in binding of atrazine. On the other hand, the soil amended with farmyard manure had a higher content of carboxylic units, which could be responsible for hydrogen bonding between atrazine and OM. Dominance of hydrogen bonds compared to hydrophobic interactions can be responsible for the lower desorption capacity observed with the farmyard manure soil. The stronger hydrogen bonding can reduce the leaching of atrazine into drinking water resources and runoff to rivers and other surface waters.

Optimization of phenolic compounds analysis by capillary electrophoresis

Operational parameters like migration time, temperature, voltage, composition of background electrolyte and content of organic modifier were optimized in CZE for the determination of lignin-like phenolic compounds. The applied background electrolyte buffer consisted of a Na(2)B(4)O(7), KH(2)PO(4) aqueous solution, pH 9.15 using acetonitrile as organic modifier with UV-detection. Compounds, such as acetosyringone, acetovanillone, syringealdehyde, p-hydroxyacetophenone, vanillin, syringic acid, ferulic acid, p-hydroxybenzaldehyde, p-coumaric acid, vanillic acid and p-hydroxybenzoic acid were applied as reference compounds. The quality and quantity of different phenolic compounds obtained upon alkaline CuO oxidation of a commercial humic acid were determined with CZE using ethylvanillin as internal standard. The optimized CZE revealed has being an appropriate method since it is quick, sensitive and quantitative and does not require a time-consuming sample preparation.

One-step extraction and concentration of estrogens for an adequate monitoring of wastewater using ionic-liquid-based aqueous biphasic systems†

Ethinylestradiol (EE2) is a synthetic hormone that has been recognized as one of the most prominent endocrine disruptors found in the aqueous environment. Nevertheless, the low content of EE2 in wastewater makes its identification/quantification unfeasible - a major drawback for the evaluation of its persistence and environmental impact. In this context, a novel extraction/concentration method for EE2 from wastewater is proposed here based on aqueous biphasic systems composed of ionic liquids (ILs). Aqueous biphasic systems formed by several hydrophilic ILs and KNaC4H4O6 were initially screened and optimized, with extraction efficiencies of EE2 for the IL-rich phase ranging between 92 and 100%. Remarkable results were obtained with systems that allow the complete extraction of EE2 in a single-step, and without loss of EE2 or the saturation of the extractive phase. Further, the concentration factors of EE2 attainable with these systems were investigated by a suitable manipulation of the composition of the phase-forming components and the corresponding volumes of the coexisting phases. An outstanding concentration of EE2 up to 1000-fold (from ng L-1 to μg L-1) in a single extraction and concentration step was achieved for the first time with IL-based aqueous biphasic systems. These systems are straightforwardly envisaged for the monitoring of wastewater as one-step extraction and concentration routes for a wide array of endocrine disrupting chemicals while allowing an adequate evaluation of their environmental impact.

Application of dispersive liquid-liquid microextraction for estrogens' quantification by enzyme-linked immunosorbent assay.

Estrogens, such as 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), are the major responsible for endocrine-disrupting effects observed in aquatic environments due to their high estrogenic potency, even at concentrations ranging from pgL(-1) to ng L(-1). Thus, it is essential to develop analytical methodologies suitable for monitoring their presence in water samples. Dispersive liquid-liquid microextraction (DLLME) was used as a pre-concentration step prior to the quantification of E2 and EE2 by enzyme-linked immunosorbent assay (ELISA). First, an evaluation of the effect of DDLME on the E2 and EE2 ELISA calibration curves was performed. Since the extraction procedure itself had an influence on the ELISA optical density (OD), it became necessary to subject, not only the samples, but also all the standards to the DLLME process. Working ranges were determined, being between 1.2 and 8000 ng L(-1), for E2, and between 0.22 and 1500 ng L(-1), for EE2. The influence of organic matter, both in the extraction and quantification, was evaluated and it was observed that its presence in the solution did not affect considerably the calibration curve. Recovery rates were also determined, ranging from 77% to 106% for ultrapure water and from 104% to 115% for waste water samples, the most complex ones in what concerns matrix effects. Results obtained when applying the proposed method to real water samples can be considered quite satisfying. Moreover, the obtained working ranges encompass values generally reported in literature, confirming the practical use of the method for environmental samples.

Evaluation of the anthropogenic input of caffeine in surface waters of the north and center of Portugal by ELISA.

This study comprises the development of an enzyme-linked immunosorbent assay (ELISA) for the quantification of caffeine in complex aqueous matrices without any sample clean-up procedure. Salinity and dissolved organic matter were selected as potential interfering agents. The addition of a sample buffer containing bovine serum albumin (BSA) prior to the sample was found to decrease the influence of those interfering agents. The working range of the developed method was 0.1-100 μg L(-1). Quantification of caffeine was possible in 43 out of 51 real aqueous samples, at values between <LOD and 15 μg L(-1). Results correlate well with those obtained by LC-MS/MS. To the best of our knowledge this is the first study dealing with the quantification of caffeine in Portugals surface waters.

Photosensitized Degradation of 17β-estradiol and 17α-ethinylestradiol: Role of Humic Substances Fractions.

Photodegradation of 17α-ethinylestradiol (EE2) and 17β-estradiol (E2) was investigated under simulated solar radiation. Photodegradation kinetics in the absence and presence of humic substances (HSs) fractions (humic acids [HAs], fulvic acids [FAs], and XAD-4), were compared. Although all three fractions were responsible for a noticeable increase on photodegradation rates, the effects were greater for FA and XAD-4. Half-life time decreased from 46 and 94 h (direct photodegradation) for EE2 and E2, respectively, to 6.4, 2.1, and 2.7 h (for EE2) and 5.7, 2.9, and 3.1 h (for E2) in the presence of HAs, FAs, and XAD-4, respectively. The XAD-4 fraction results were similar to those of FAs, which is considered the most photochemically active fraction of HSs. Studies were also conducted in organic matter-rich environmental water matrices. After 5 h, photodegradation ranged from 44 to 94% for EE2 and from 27 to 95% for E2, compared with 16% for EE2 and 6% for E2 in ultrapure water. The maximum photodegradation was obtained in an estuarine water sample, known to be rich in FAs and XAD-4 fractions and poor in HAs, showing that not only is the presence of organic matter an important factor for the photodegradation increase, as also the type of organic matter is determinant.

Sorption behavior of EE2 on soils subjected to different long-term organic amendments

The transport and fate of hydrophobic organic contaminants in the environment involve complex phenomena that are influenced by many processes that include sorption by soil components. Sorption behavior of EE2 molecules onto different soil samples was studied and results correlated with the content and type of organic matter present. The highest K value, among all soils presented in this study, was obtained for soil fertilized with compost (1.22) which presented the highest organic carbon content. Also the sorption behavior depends greatly on the soil specific organic matter characteristics. A strong positive correlation was observed between aromatic and carboxylic units and K(OC) values. The results also suggested an association of the EE2 aromatic nuclei face to face with the surface and/or another EE2 molecule and also sorbent-sorbate interactions due to hydrogen or covalent bonding, likely to occur due to the presence of phenolic function at C-3 and hydroxyl function at C-17 of the EE2 molecules that can react with carboxylic functional groups of soil organic matter. The stronger EE2 sorbs to soil organic matter lower is the leaching into drinking water resources and runoff to rivers and surface water, minimizing its residual toxicity.

Development of an ELISA procedure to study sorption of atrazine onto a sewage sludge-amended luvisol soil

Pesticides may contaminate ground and surface waters and one of the major factors governing this property is soil sorption. Sorption can be assessed by batch equilibrium technique which produces lots of extracts with high dissolved organic carbon concentration in which the pesticide concentration has to be determined. We developed an ELISA procedure to analyse atrazine based on polyclonal antibodies (C193) for which tracer structure and dilutions of immunochemical reagents were adapted to fit the purpose. After a 1000-fold dilution (or after an SPE clean-up procedure) extracts of a sewage-sludge amended luvisol (used as an example application of the methodology developed) could be reliably analysed. The Freundlich model is able to describe adsorption for this system (r(2)=0.977) delivering a distribution coefficient K(F) of 1.6±0.2 (mg kg(-1)) (mg L(-1))(-N) and an isotherm nonlinearity factor N of 0.70±0.09.

Effect of natural aquatic humic substances on the photodegradation of estrone.

Photodegradation of estrone (E1) was investigated under simulated solar radiation in absence and presence of the different fractions of humic substances (HS), namely humic acids (HA), fulvic acids (FA) and XAD-4 fraction. The pseudo-first order photodegradation rate constants increased from 0.1137 h(-1), in ultrapure (MQ) water, to 0.1774, 0.1943 and 0.3109 h(-1), in presence of HA, FA and XAD-4, respectively. Half-life time decreased from 6.10 h in MQ water to 3.91, 3.57 and 2.23 h in presence of HA, FA and XAD-4, respectively. These results evidence the relevant photosensitizing effect of XAD-4 fraction of HS on the degradation of E1, which, to the best of our knowledge have never been studied. Photodegradation studies were also conducted in organic matter-rich environmental aquatic matrices, namely fresh, estuarine and waste water. After 2 h, photodegradation achieved values ranged between 35.6 and 57.1% in natural water samples, compared with 26.4% in ultrapure water. The higher photodegradation occurred in an estuarine water sample, known to be rich in XAD-4 fraction and poor in HA, indicating that not only the presence of organic matter, but also its type, are determinant in the E1 photodegradation rate. Finally, the use of sodium azide as singlet oxygen ((1)O2) scavenger during the phototransformation of E1 in ultrapure and in two wastewater samples allowed to conclude that (1)O2 has an important role in the E1 photodegradation.

Comparison between MEKC and UV spectral deconvolution to follow sorption experiment in soil.

In this study a simple and rapid procedure for monitoring sorption of atrazine onto soil samples was developed. This method is based on a multiwavelength UV spectral deconvolution (UVSD) where the UV spectrum of a sample is considered as a linear combination of absorption spectra, named reference spectra. The combination of the reference spectra allows the restitution of the shape of the UV spectrum of any unknown sample. In order to evaluate the accuracy of this method, a sorption study of atrazine to three different soil samples was monitored using both UVSD and micellar electrokinetic chromatography (MEKC) methods. The Freundlich parameters (K(F) and N) obtained for all soil samples tested were similar for both methods and UVSD has proven to be an accurate methodology, since the results did not present statistical significant differences at 95% confidence level. Moreover, the LOD obtained using UVSD presented lower values (0.066-0.12mgL(-1)) than the one obtained using MEKC (0.26mgL(-1)). The proposed UVSD method has been proven useful as a valid alternative, to the more common procedures to follow sorption experiment in soil matrix samples with no need of sample pre-treatment or column conditioning. This method is much faster and requires less sample manipulation than traditional analytical separation methods. Moreover, most modern spreadsheet-applications, such as Excel, now include statistical packages that allow performing multi-linear regression, which make this approach particularly inexpensive since the only requirement is a UV spectrometer. The regression output was made using the Microsoft Excel, a very easy and fast program, allowing anyone, with less knowledge about complex statistical programs, to perform the UV spectral.