Ultra-pressure liquid chromatography-electrospray tandem mass spectrometry for multiresidue determination of pesticides in water.

A multiresidue analysis method has been developed for the determination of pesticides in water by ultra-performance liquid chromatography (UPLC) combined with tandem mass spectrometry (MS/MS). The selected pesticides represent a broad range of polarity and volatility [benzoylcyclohexanedione (mesotrione and sulcotrione); chloroacetamide (acetochlor, alachlor, dimethenamide, and metolachlor); phenoxyacetic acid (2,4-D and MCPA); phenoxypropionic (dichloprop and mecoprop); phenylurea (chlortoluron, diuron, isoproturon, linuron, and metoxuron); sulfonylurea (foramsulfuron, iodosulfuron, and nicolsulfuron); triazine (atrazine, cyanazine, desethylatrazine (DEA), desisopropylatrazine (DIA), simazine, and terbutylazine)]. The analytes were extracted using solid-phase extraction (SPE). The separation was carried out on an acquity UPLC BEH C18 column (1.7 microm, 50 mm x 1 mm ID) using a gradient elution profile and mobile phase consisting of 0.1% formic acid in water and acetonitrile. The pesticides were detected with a tandem mass spectrometer after being ionised positively or negatively (depending on the molecule) using an electrospray ionisation (ESI) source. To achieve the suitable extraction conditions for sample preparation, several parameters affecting the efficiency of SPE such as the nature of the sorbent and the eluent, extractant volume and pH were studied. The best recovery was obtained by the extraction with an Oasis HLB cartridge and 3 mL of a solution of acetonitrile/dichloromethane (1:1, v/v) at pH 2. The average recoveries of the pesticides in different samples ranged from 82 to 109%. The weight least squares (WLS) linear regression was used to calculate the limits of detection and quantification (LOD and LOQ) because the dispersion was heteroskedastic. All the pesticides could be correctly quantified at a concentration level of 50 ng L(-1) and most of them could be detected at a concentration inferior or equal to 8 ng L(-1). Efficiency and robustness of this method were evaluated by the analysis of several samples of real natural water.

Photocatalytic degradation of pesticides in pure water and a commercial agricultural solution on TiO2 coated media.

Heterogeneous photocatalysis of pesticides is an effective process for removing pesticides from pure water. With a view to treating real agricultural effluents, this paper deals with the degradation of the chlortoluron and cyproconazole pesticides in pure water and the treatment of commercial solutions by photocatalysis on TiO2 coated media. The process was effective in degrading and mineralizing the pesticides. The changes of the fate of heteroatoms showed that during irradiation of the chlortoluron and cyproconazole, NH4+ and NO3(-) ions were produced. A release of chloride ions was observed from the beginning of the irradiation and stoichiometry was achieved. The photodegradation of chlortoluton and cyproconazole in commercial solutions was studied. For the degradation of chlortoluton in a commercial solution, the mineralization was completely achieved whereas in the case of the commercial cyproconazole solution, the degradation kinetic was lower. These results highlight the fact that the chemical nature of the additives in the commercial pesticide solutions does significantly affect the degradation yield of the target compound by photocatalysis.

Mass transfer in VOC adsorption on zeolite: experimental and theoretical breakthrough curves.

From experimental results of adsorption of volatile organic compounds (VOCs) on zeolite, we propose simulations of the breakthrough curves based on the Linear Driving Force model. Experiments were run on fixed beds of hydrophobic commercial zeolites. Pollutants chosen are from several chemical classes with different polarities. A good agreement between experimental and numerical results is found when an adjustable value of the internal mass-transfer coefficient is used. A constant value of effective diffusivity is found independent of the nature and the amount of VOCs adsorbed. A relation linking intrapellet mass-transfer coefficient and equilibrium constant is proposed, including the average effective diffusivity, to make predictions of breakthrough curves for any kind of volatile organic pollutant in gaseous effluents.