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GC X GCTOFMS OF SYNTHETIC PYRETHROIDS IN FOODS SAMPLES
COCHRAN, J., P. KAUFFMAN, T. E. HIEBER, AND J. N. MORGAN. GC X GCTOFMS OF SYNTHETIC PYRETHROIDS IN FOODS SAMPLES. Presented at Florida Pesticide Residue Workshop, Orlando, FL, July 16 - 20, 2006.
The overall goal of this research program is to identify those chemicals, pathways, and activities that represent the highest potential exposures to children and to determine the factors that influence these exposures. The following objectives will address this goal:
Revise and refine the existing research plan for children's exposure measurements research.
Collect measurement data on children's exposures.
Provide analytical support to children's pesticide exposure research.
Develop analytical methods for pesticides in duplicate diet food samples.
Develop and apply analytical methods for other chemicals including but not limited to brominated diphenyl ethers, phthalates, perfluorinated chemicals.
Evaluate the impact of chiral chemistry on the risk to children and exposure assessment.
Provide support to the National Children's Study.
Perform data analyses to fill critical data gaps.
Conduct analyses of dietary samples and refine the dietary model for the dietary exposure algorithm.
Pyrethrins are natural insecticides in the extract of chrysanthemum flowers1. Pyrethroids are synthetic forms of pyrethrins, and many are halogenated (F, Cl, Br). Synthetic pyrethroids have become popular replacements for organophosphorus pesticides, which have become increasingly regulated due to health and environmental concerns. Synthetic pyrethroids were designed to be more stable than pyrethrins, and therefore have the potential to be found in the environment, and in food, as trace residues. They are highly toxic to aquatic organisms and some may be endocrine disruptors and/or carcinogens. Typical methods for their analysis include gas chromatography - electron capture detector (GC-ECD)2, GC - electrolytic conductivity detector (ELCD)3, and GC - mass spectrometry (MS)4.
A relatively new way to solve separation problems for complex samples, including those for food analysis, is to use comprehensive two-dimensional GC (GCxGC). GCxGC increases peak capacity by applying two independent separations to a sample in one analysis. Typically, GCxGC involves a serial column configuration (employing orthogonal phases) separated by a thermal modulator. Due to modulation, most GCxGC peaks are on the order of 50 to 250 ms wide, requiring a fast detector. When mass spectrometry is used, only time-of-flight (TOF) has the necessary acquisition rates (hundreds of spectra/sec). The ability of the thermal modulator to narrow peaks (thereby increasing their height) prior to their detection also affords the ability to increase TOFMS sensitivity, which can be important for the analysis of trace levels of pesticides in food samples, not only to increase their detection, but also to allow moderate (1 to a few microliters) sample sizes to be introduced to the GC. Keeping the sample introduction volume low, especially in food analysis, helps preserve the integrity of the chromatographic system.
GCxGC with a flame ionization detector (FID) was recently employed for the analysis of pyrethrins (cinerins, jasmolins, pyrethrins) in a chrysanthemum extract5. Since these pyrethrins are thermally labile, on-column injection and, very short primary and secondary columns were used. Fast GCxGC with a short primary column allowed the unbiased determination of the pyrethrins in the complex extract, but the technique was not used for synthetic pyrethroid analysis. The paper offered here demonstrates GCxGC-TOFMS for the analysis of synthetic pyrethroids, with an emphasis on those that contain halogens. A pyrethroid-spiked composite food extract is used to demonstrate the utility of GCxGC-TOFMS for complex matrices.