No abstract

This paper reviews the application of various modes of solid-phase microextraction (SPME) for the analysis of pesticide residues in fruits and vegetables. SPME is a simple extraction technique that eliminates the use of solvent, and it is applied for the analysis of both volatile and nonvolatile pesticides. SPME has been successfully coupled to both GC and LC. The coupling with GC has been straightforward and requires little modification of existing equipment, but interfacing with LC has proved challenging. The external standard calibration technique is widely used for quantification, while standard addition and internal or surrogate standards are mainly used to account for matrix effects. All parameters that affect the extraction of pesticide residues from fruits and vegetables, and therefore need to be optimized, are also reviewed. Details of the characteristics of analytical procedures and new trends in fiber production using sol-gel technology and molecularly imprinted polymers are discussed.

Experimental Reagents and solutionsAll solvents used were of HPLC grade. Methanol, acetone, ethyl acetate, acetonitrile, hexane and diethyl ether were purchased from Fischer Scientific, Loughborough, UK. Deionized water and hexane were filtered through a 0.45-μm membrane filter purchased from Millipore. Anhydrous sodium sulfate was purchased from J. T. Baker, NJ, USA.The use of high-purity reagents and solvents helps to minimize interference problems. The pesticide standards (acephate, dimethoate, malathion, diazinon, quinalphos, chlorpyrifos, profenofos, α-endosulfan, b-endosulfan, chlorothalonil and carbaryl) were 90.0 -99.5% pure and purchased from AccuStandard Inc. New Haven, CT, USA.All pesticides were dissolved in hexane at 1000 mg/kg concentrations as stock solutions. A mixture containing 0.01 -0.5 mg/kg of each pesticide in hexane was prepared from the stock solutions and as the working solution. In order to avoid any influence on the results from the possible degradation of pesticides, the working solution was freshly prepared every day.1-Chloro-4-fluorobenzene (1 mg/kg) was used as an internal standard to compensate for any sample and injection volume changes, and was added to the vial prior to GC analysis.

Microalgae biomass can produce high quantities of biochemicals that can be used in various applications such as biodiesel, biogas, and aquaculture feed. The potential of sterilizing wastewater for microalgae-based wastewater treatment on a lab scale is well introduced. However, the operation cost for large-scale microalgae cultivation in wastewater treatment plants is high if using sterilising wastewater as the growth medium. The present study aimed to evaluate the growth of Scenedesmus sp., Chlorococcum aquaticum, Ankistrodesmus augustus, and Haematococcus pluvialis in non-sterilised domestic wastewater and their potential for pollutant removal in wastewater. The microalgae were cultivated in different concentrations of non-sterilised domestic wastewater, collected from a primary wastewater plant of a national sewerage company in Malaysia. Each species’ capacity for growth and the removal of pollutants were assessed. The results showed that the cell density, maximum biomass productivity, and biomass concentration of H. pluvialis, Scenedesmus sp., and C. aquaticum in 100% wastewater were significantly higher than the standard medium. Higher biomass concentration was obtained from H. pluvialis and C. aquaticum in 100% wastewater (815 g/L and 775.83 mg/L); nevertheless, Scenedesmus sp. in 100% wastewater yielded the highest specific growth rate (0.798 d−1) and the maximum biomass productivity (99.33 mg/L/day). Scenedesmus sp. in 100% wastewater also achieved better removal efficiency of total nitrogen (TN), total phosphorus (TP), and ammonia (N-NH4) with more than 90%. All tested microalgae species successfully remove nitrogen, ammonium, and phosphorus and reach the concentration limits set by the Department of the Environment, Malaysia. This study demonstrated that microalgae can grow well in non-sterilised domestic wastewater while simultaneously removing nitrogen and phosphorus effectively.