Isabel Garrido

Determination of spirocyclic tetronic/tetramic acid derivatives and neonicotinoid insecticides in fruits and vegetables by liquid chromatography and mass spectrometry after dispersive liquid–liquid microextraction

Dispersive liquid-liquid microextraction was used to preconcentrate three spirocyclic tetronic/tetramic acid derivatives (spirotetramat, spiromesifen and spirodiclofen) and five neonicotinoid (thiamethoxam, chlotianidin, imidacloprid, acetamiprid and thiacloprid) insecticides previously extracted from fruit and vegetable matrices with acetonitrile. The organic enriched phase was evaporated, reconstituted in 25μL acetonitrile and analyzed by reversed-phase liquid chromatography with tandem mass spectrometry using a triple quadrupole in selected reaction monitoring mode. Enrichment factors in the 15-100 range were obtained. A matrix effect was observed, the detection limits varying between 0.025 and 0.5ngg(-1), depending on the compound and the sample matrix. The developed method was applied to the analysis of 25 samples corresponding to five different fruit and vegetable matrices. Only thiamethoxam was detected in a lemon sample at a concentration close to the quantification limit, and spiromesifen and spirotetramat at concentrations between 11.6 and 54.5ngg(-1).

Dispersive liquid-liquid microextraction for the determination of new generation pesticides in soils by liquid chromatography and tandem mass spectrometry.

A sensitive method for the determination of five new generation pesticides (chlorantraniliprole, spirotetramat, spiromesifen, spirodiclofen and flubendiamide) in soil samples has been developed using liquid chromatography and tandem mass spectrometry (LC-MS(2)) with a triple-quadrupole in the multiple reaction monitoring mode. The target analytes are released from the solid matrix by single-phase extraction in acetonitrile (SLE), this organic phase being used as dispersant solvent in the dispersive liquid-liquid microextraction (DLLME) step. The different parameters affecting the extraction efficiency in DLLME were carefully studied, being 1.5mL of acetonitrile extract (disperser solvent), 125μL carbon tetrachloride (extraction solvent) and 10mL aqueous solution, the selected conditions. The enriched organic phase was evaporated, reconstituted with 50μL acetonitrile and injected into a liquid chromatograph with a mobile phase composed of acetonitrile and 0.1% (v/v) formic acid under gradient elution and a C8 stationary phase. Detection limits in the 0.0015-0.0090ngg(-1) range were obtained. Insecticide concentrations ranging from 0.03 to 197ngg(-1), depending on the compound, were found in the soil samples analysed. The recovery values obtained by SLE-DLLME-LC-ESI-MS(2) for three spiked soils at three concentration levels varied between 87 and 114%, with RSDs of between 5.5 and 14%.

Reclamation of Water Polluted with Flubendiamide Residues by Photocatalytic Treatment with Semiconductor Oxides.

The photodegradation of flubendiamide (benzenedicarboxamide insecticide), a relatively new insecticide was investigated in aqueous suspensions binary (ZnO of and TiO2) and ternary (Zn2TiO4 and ZnTiO3) oxides under artificial light (300–460 nm) irradiation. Photocatalytic experiments showed that the addition of semiconductors, especially ZnO and TiO2, in tandem with an electron acceptor (Na2S2O8) enhances the degradation rate of this compound in comparison with those carried out with catalyst alone and photolytic tests. The photocatalytical degradation of flubendiamide using ZnO/Na2S2O8 and TiO2/Na2S2O8 followed first‐order kinetics. In addition, desiodo‐flubendiamide was identified during the degradation of flubendiamide. Finally, application of these reaction systems in different waters (tap, leaching and watercourse) showed the validity of the treatments, which allowed the removal of flubendiamide residues in these drinking and environmental water samples.

Combination of solvent extractants for dispersive liquid-liquid microextraction of fungicides from water and fruit samples by liquid chromatography with tandem mass spectrometry

A multiresidue method was developed to determine twenty-five fungicides belonging to three different chemical families, oxazoles, strobilurins and triazoles, in water and fruit samples, using dispersive liquid-liquid microextraction (DLLME) and liquid chromatography/tandem mass spectrometry (LC-MS2). Solid-liquid extraction with acetonitrile was used for the analysis in fruits, the extract being used as dispersant solvent in DLLME. Since some of the analytes showed high affinity for chloroform and the others were more efficiently extracted with undecanol, a mixture of both solvents was used as extractant in DLLME. After evaporation of CHCl3, the enriched phase was analyzed. Enrichment factors in the 23-119 and 12-60 ranges were obtained for waters and fruits, respectively. The approach was most sensitive for metominostrobin with limits of quantification of 1ngL-1 and 5ngkg-1 in waters and fruits, respectively, while a similar sensitivity was attained for tebuconazole in fruits. Recoveries of the fungicides varied between 86 and 116%.

Determination of synthetic phosphodiesterase-5 inhibitors by LC-MS2 in waters and human urine submitted to dispersive liquid-liquid microextraction

High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS2) with a triple quadrupole is proposed for determining the synthetic phosphodiesterase-5 inhibitors, sildenafil, tadalafil and vardenafil, and the active metabolite N-desmethyl sildenafil. The method was successfully applied to the analysis of waters of different origins and human urine samples. Dispersive liquid-liquid microextraction (DLLME) was applied in the classical way for water analysis, whereas a previous extraction into an organic solvent was necessary for urine samples, the acetonitrile extract being used as dispersant solvent in the DLLME step. The analytes were determined by LC-ESI-MS2 in the multiple reaction monitoring mode. Detection limits were in the 5-50 and 15-250ngL-1 ranges for water and urine samples, respectively. The repeatability was calculated using the relative standard deviation, obtaining values of between 3.6% and 10.1%. The enrichment factors were between 75 and 81. Accuracy of the procedure was calculated through recovery assays and average recoveries ± SD (n = 48) of 93.6 ± 3.5 and 91.1 ± 3.5 were obtained for water and urine samples, respectively. None of the samples analyzed contained the target compounds, at least above the corresponding detection limits.

Trial of solar heating methods (solarization and biosolarization) to reduce persistence of neonicotinoid and diamide insecticides in a semiarid Mediterranean soil

This paper reports the use of solar heating techniques, solarization (S) and biosolarization (BS) as a strategy for the environmental restoration of soils containing neonicotinoid, acetamiprid (AC), imidacloprid (IM) and thiamethoxam (TH), and diamide, chlorantraniliprole (CL) and flubendiamide (FB) insecticide residues. For this, a semiarid Mediterranean soil (Haplic calcisol) was covered with low-density polyethylene (LDPE) during the hot season, to raise the maximal soil temperatures. Compost from sheep manure (CSM), meat-processing waste (MPW) and sugar beet vinasse (SBV) were used as organic wastes. The results showed that both S and BS increase insecticide disappearance rates compared with the non-disinfected soil, the increase in soil temperature and added organic matter playing a key role. The dissipation rates of TH and AC in soil were satisfactorily described by first-order (monophasic) kinetics, while IM, CL and FB showed a deviation from exponential behaviour. For them, the best results were obtained applying biphasic kinetics with a rapid initial degradation followed by a slower decline of their residues. The findings suggest that S and BS (especially using MPW) can be considered as a valuable tool for enhancing the detoxification of soils polluted with these insecticides.

Use of different organic wastes in reducing the potential leaching of propanil, isoxaben, cadusafos and pencycuron through the soil

In this study, we examined the effect of four different organic wastes (OW)—composted sheep manure (CSM), spent coffee grounds (SCG), composted pine bark (CPB) and coir (CR)—on the potential groundwater pollution of propanil and isoxaben (herbicides), cadusafos (insecticide) and pencycuron (fungicide) under laboratory conditions. For this purpose, leaching studies were conducted using disturbed soil columns filled with a clay loam soil (Hipercalcic calcisol). The addition of organic matter (OM) drastically reduced the movement of the studied pesticides. The results obtained point to the interest in the use of agro-industrial and composted OW in reducing the groundwater pollution by pesticide drainage.

Solar photocatalytic reclamation of agro-waste water polluted with twelve pesticides for agricultural reuse

This study aims to demonstrate a technically feasible alternative to remove pesticide residues from agro-waste water produced in farms from remnants in containers and treatment tanks, rinse in tanks after treatments, and cleaning of machines and equipment. For this, the photocatalyzed degradation of 12 pesticides commonly used on vegetables, vines, citrus and fruit crops was investigated in aqueous suspensions of TiO2 in tandem with Na2S2O8 at pilot plant scale under natural sunlight in Murcia (SE of Spain) during summer and winter seasons. Previously, preliminary experiments were carried out at laboratory scale using a photoreactor to optimize the photocatalyst (200 mg L-1) and oxidant (250 mg L-1) concentrations on the rate constants of the studied pesticides. The photodegradation of all pesticides can be modelled assuming a pseudo-first-order kinetics. The time needed for disappearance of 90% (DT90) of the studied pesticides, was lower than 4 h in summer in all cases with the exception of cyproconazole (4.9 h), while, cyproconazole (8.9 h), metalaxil (6.1 h) and propyzamide (7.9 h) showed DT90 higher than 6 h in winter. The reaction rate was enhanced 3-fold in summer season, which is directly correlated to the higher accumulated fluence per time received during this season (about a factor of 2.9 higher than in winter). In both cases, the higher and lower degradation rates were obtained for cyprodinil and cyproconazole, respectively. The total fluence to get a 90% reduction (H90) ranged from 4.6 to 5.2 J cm-2 (cyprodinil) to 71.5-76 J cm-2 (cyproconazole).

Solar reclamation of wastewater effluent polluted with bisphenols, phthalates and parabens by photocatalytic treatment with TiO2/Na2S2O8 at pilot plant scale

Investigations of anthropogenic contaminants in fresh- and wastewater have shown a wide variety of undesirable organic compounds such as Endocrine Disruptors (EDs). As a result, wastewater treatments using innovative technologies to remove those organic compounds are required. In this paper, the photodegradation of six EDs in wastewater at pilot plant scale is reported. The EDs were bisphenol A, bisphenol B, diamyl phthalate, butyl benzylphthalate, methylparaben and ethylparaben. Commercial TiO2 nanopowders (P25, Alfa Aesar and Kronos vlp 7000) were used as photocatalysts. The operating variables (type and loading catalyst, effect of electron acceptor and pH) were previously optimized under laboratory conditions. The results show that the use of TiO2 alongside an electron acceptor like Na2S2O8 strongly enhances the degradation rate of the studied compounds compared with photolytic tests, especially P25. The oxidation rates of the EDs at pilot plant scale were calculated following the disappearance of the target compound as a function of fluence (H). The ED degradation followed a pseudo-first order kinetics in all cases. In our experimental conditions, the half-fluence (H50) varied from 79 to 173 J cm-2 (photolytic test), 10-117 J cm-2 (TiO2 vlp 7000) and 3-58 J cm-2 (TiO2 P25), for bisphenol B and butyl benzylphthalate, respectively. It is concluded that solar photocatalysis using the tandem TiO2/Na2S2O8 can be considered as an environmental-friendly tool for water detoxification and a sustainable technology for environmental remediation, especially in the Mediterranean Basin, where many places receive more than 3000 h of sunshine per year. Although the cost depends on the nature of the pollutant, the treatment cost was estimate to be about 150 € m-3 for photocatalytic treatment with TiO2 P25.

Enhanced degradation of spiro-insecticides and their leacher enol derivatives in soil by solarization and biosolarization techniques

The leaching potential of three insecticides (spirodiclofen, spiromesifen, and spirotetramat) was assessed using disturbed soil columns. Small quantities of spirodiclofen and spiromesifen were detected in leachate fraction, while spirotetramat residues were not found in the leachates. In addition, the transformation products (enol derivatives) are relatively more mobile than the parent compounds and may leach into groundwater. Moreover, the use of disinfection soil techniques (solarization and biosolarization) to enhance their degradation rates in soil was investigated. The results show that both practices achieved a reduction in the number of juvenile nematodes, enhancing in a parallel way degradation rates of the insecticides and their enol derivatives as compared with the non-disinfected soil. This behavior can be mainly attributed to the increase in soil temperature and changes in microbial activity. All insecticides showed similar behavior under solarization and biosolarization conditions. As a consequence, both agronomic techniques could be considered as suitable strategies for detoxification of soils polluted with the studied pesticides.