Simple analytical method for determination of pesticide residues in human serum by liquid chromatography tandem mass spectrometry

The aim of this study was to develop an analytical method for the determination of residues of organophosphorus and carbamate pesticides which are widely used in Tunisia. This method involves a liquid-liquid extraction procedure followed by liquid chromatography tandem mass spectrometry (LC/MS/MS) for the identification and quantification of compounds. Ionization of molecules was performed by the electrospray mode. Multiple reactions monitoring (MRM) was the acquisition mode used for the monitoring of two MS/MS transitions for each compound. The average recoveries obtained, at three different fortification levels, ranged between 65% and 106% for most of the pesticides studied, except for methamidophos (lower than 25%).The linearity of the method was in the range of 5 to 50 μ g/L with a correlation coefficient from 0.995 to 0.999, depending on the analyte. The estimated limit of detection and limit of quantification were 2 μ g/L and 5 μ g/L, respectively. The precision of the analytical procedure was satisfactory and the coefficients of variation, evaluated at three concentration levels were lower than 15% for most pesticides studied. The application of the method was investigated in a population of agricultural workers chronically exposed to various pesticides some of which, such as carbofuran, carbendazim, methomyl and pirimicarb, were detected in some serum samples.     

Mapping Social Networks for Performance Evaluation of Irrigation Water Management in Dry Areas

Collaboration between actors is an important determinant of water governance, particularly in developing countries suffering from lack of institutional and organizational performances for water management. The objective of this paper is to use the social network (SN) concept in bringing depth to the understanding of local irrigation governance in three irrigated schemes located in dry regions of southern Tunisia. Local stakeholders in the considered schemes interact around different water-related issues. These include authorizations for access to water, extension services for irrigated crops, training on the use of irrigation technologies, and finance and subsidies of irrigation water saving equipment. We considered each of these types of interactions as different tie and we mapped social networks around each of them. For each network, actors’ densities, frequencies, and weight were reported. The results were revealing that better performances of water management are observed in areas with high SN density and high centrality of water users’ associations. The relative “weights” of actors in the three considered areas were significantly different, indicating that the application of a standard decentralization process of irrigation water may result in different local organizational arrangements, depending on patterns of social interactions.