Wednesday, October 19, 2011

Pesticide Detection Results

Last week the students turned in revised versions of their abstracts and figures from the ELISA and GC-MS analyses that we performed on a water sample from the Haw River in Alamance County. The laboratory protocol was based on an article from the Journal of Chemical Education and is available on request.

Jacqueline Meadows has agreed to let me share her abstract and figures on the blog so you can see our results. Luckily, both ELISA and GC-MS analysis indicated acceptably low levels of pesticides in the original water sample.

Pesticides are chemicals used to increase the amount of yield from crops. Though these compounds are useful in the productivity of farming, they may also have harmful implications when they run off into waterways, like lakes and rivers. The purpose of this experiment was to analyze the concentration of two pesticides, atrazine and simazine, in a water sample taken from the Haw River. The sample was tested as obtained from the river and also spiked with relatively high concentrations of atrazine and simazine. The concentrations were evaluated using ELISA and gas chromatography mass spectrometry (GC-MS). The ELISA method revealed an original sample concentration of 0.890±0.123 ppb of atrazine and a spiked sample concentration of 112±0.1 ppb of atrazine. The GC-MS, however, reported an atrazine concentration of 0.00±0.26 ppb and a simazine concentration of 1.74±0.05 ppb in the original sample, and concentrations of 73.4±0.2 ppb and 129±0.04 ppb in atrazine and simazine, respectively, for the spiked sample. The average retention time of atrazine was 12.65 minutes and that of simazine was 12.55 minutes for the GC experiment. The ELISA data was more sensitive than the GC because it was able to detect smaller amounts of the pesticide, whereas the GC method was able to quickly and efficiently separate the different pesticides for analysis.


Figure 1: ELISA data for atrazine standards.
Figure 2: Gas chromatography peak areas for given concentrations of atrazine and simazine standards.

(Abstract and Figures courtesy of Jacqueline Meadows)

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