Submitted to: Journal of Separation Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/5/2006
Publication Date: 3/20/2006
Citation: Janska, M., Lehotay, S.J., Mastovska, K., Hajslova, J., Alon, T., Amirav, A. 2006. A simple and inexpensive "solvent in silicone tube extraction" approach and its evaluation in the gas chromatographic analysis of pesticdes in fruits and vegetables. Journal of Separation Science.(29)66-88. Interpretive Summary: Effective and efficient analytical methods are needed to detect pesticide residues in fruits and vegetables. Rapid methods usually do not detect very low amounts of the pesticides because it takes time to concentrate the residues in a final extract. Furthermore, other chemicals in the food sample are also concentrated to the same extent as the pesticides in traditional methods, which interfere in the detection. This research study evaluated a new way to concentrate the pesticides, but block the interfering chemicals. The new approach is called “solvent in silicone tube extraction” (SiSTEx), in which an organic solvent is placed in a thin silicone tube surrounded by the watery sample. Many of the pesticides transfer into and through the tubing into the solvent, and most of the other chemicals stay in the watery sample. The pesticides are more highly concentrated in the solvent and very low levels can be detected from the sample. This new approach is simple, cheap, and effective, and can be used to lower detection limits of pesticide residues in food samples.
Technical Abstract: A novel, simple, and inexpensive approach to sorptive extraction, which we call solvent in silicone tube extraction (SiSTEx), was applied to pesticide residue analysis and its effectiveness and efficiency were evaluated. In SiSTEx, which is a form of open tubular sorptive extraction, a piece of silicone tubing (4 cm long, 1.47 mm ID, 1.96 mm OD in this study) is attached to the cap of a 20 mL glass vial that contains the aqueous sample. The tubing has been plugged at the end dangling in the sample solution, and acetonitrile is added by syringe to the inner tube volume through a septum in the cap. A stir bar is used to mix the sample for a certain time, which allows chemicals to partition into the tubing where they diffuse across the silicone and partition into the acetonitrile. The partitioning into the silicone depends on polarity of the chemicals, with the nonpolar compounds accumulating most readily in the acetonitrile. The final extract is relatively clean of the more polar interferences that often occur in real-world samples. The final acetonitrile extract is then analyzed for the concentrated analytes. In this study, the SiSTEx approach was evaluated for the analysis of organophosphorus and organochlorine pesticides in fruits and vegetables. For analysis, gas chromatography was conducted using pulsed flame photometric and halogen specific detectors simultaneously in a split column flow configuration. The produce samples were initially extracted by a rapid acetonitrile procedure, and 5 mL of the initial extract was diluted 4-fold with water to undergo sorptive extraction for 60 min. This simple approach was able to detect 26 of the 36 pesticides at 10 ng/g or less original equivalent sample concentration with average reproducibility of 11% RSD.