Development of a carbon nanotube-coated stir bar for determination of organophosphorus pesticides in water

In this study a new adsorptive coating was developed and used for simultaneous extraction and determination of different organophosphorus pesticides (OPPs) in water samples. The adsorption phase was developed by modification of multi-walled carbon nanotubes. A magnetic stir bar was coated with the adsorption phase using sol-gel technique and used for extraction. After extraction, the analytes were desorbed thermally and determined by gas chromatography-mass spectrometry (GC-MS). The developed method was optimized and validated. The optimum condition were found as pH 6.5, salt concentration of 1% (w/v), adsorption condition of 35 degrees C and 30 min and stirring rate of 1500 rpm. Desorption step was programmed as 40 degrees C for 0.5 min, then to 300 degrees C (at 60 degrees C min(-1), held for 5 min). The acquired calibration curves were linear (0.987 <= r(2)<= 0.995) over the concentration range 0.02-8 mu g L-1. For all of the analytes, the limit of detection was <= 0.01 mu g L-1. Interday precision values were always <= 13.40% and the reproducibility of coating procedure, evaluated in term of relative standard deviation (RSD), was found acceptable (12%<= RSD <= 14%). The recoveries were in the range of 67-84% with RSD in the range of 10.2-13.5%. Good solvent and thermal resistance are the other advantages of the developed coating which makes it suitable for extraction of target compounds in water samples. The developed method was successfully applied to determine target OPPs in real samples. Based on the results Diazinon and Dichlorvos were found in more than 50% of the samples in the range of 0.06-0.27 mu g L-1. (C) 2016 Curtin University of Technology and John Wiley & Sons, Ltd.