Technical Note: Evaluation of Extraction Methodologies for the Determination of an Organochlorine Pesticide Residue in Vegetation

Abstract

Numerous extraction methodologies are used to quantify pesticide levels in vegetation. Sample availability, resource use, efficiency, time consumption, space allocation, and cost vary considerably among the commonly employed techniques. A study was conducted to compare the efficiency of microwave assisted extraction (MAE), blender homogenized extraction (BE), Soxhlet extraction (SE), the QuEChERS (“Quick, Easy, Cheap, Effective, Rugged, and Safe”) method, and a simple oven assisted extraction (OAE), to recover p,p′-DDE from the tissues of Cucurbita pepo. A hot-solvent soak of stem or root tissues in a 2-propanol/hexane mixture, OAE yields recoveries that are statistically equivalent to the other procedures. The method recovered 1800 ± 190 ng g⁻¹ and 8100 ± 900 ng g⁻¹ (BCF = 87 ± 9.7) p,p′-DDE from stem and root tissue, respectively. Recoveries for the other methods ranged from 1400–2200 ng g⁻¹ for the stems and 3600–7200 ng g⁻¹ for the roots. Statistical analyses for stem and root extraction indicate that there is no significant difference among the variances of each method. Given its simplicity, precision, and efficiency, OAE appears to be suitable for the extraction of an organic pollutant such as p,p′-DDE from plant tissues and for use in phytotechnology development and risk assessment.

KEY WORDS:

• phytoextraction
• method
• DDE

ACKNOWLEDGMENTS

Funding for the research was provided by the Program in Environmental Science and the Department of Chemistry at Muhlenberg College. We thank Joseph Hawthorne, Terri Arsenault, and William Berger of the Connecticut Agricultural Experiment Station for technical assistance.

Notes

^aOven-assisted extraction (proposed); microwave assisted extraction (US EPA Method 3546); blender extraction (J AOAC Pylypiw Method, 1993); soxhlet extraction (US EPA Method 3540); and QuEChERS (J AOAC Int, Method 2007.01).

^aValues are the mean p,p′-DDE concentrations with standard deviations in parentheses (n = 4) based on vegetation dry mass.

^bValues are log transformed variances (log s² ) used to determine relative variability of pollutant extracted via each technique.

^cDifferent capital letters within columns are significantly different (p < 0.05), one way analysis of variance (ANOVA) followed by a Tukey multiple comparison analysis.

^dDifferent capital letters within columns are significantly different (p < 0.05) variances, Bartlett's test for homogeneity of variance.

^aAverage tissue-to-soil (dry mass) concentration (92.9 ng/g) ratio for p,p′-DDE. Standard deviations in parentheses (n = 4).

^bTranslocation factor (TF), ratio of stem BCF to root BCF.

^cValues followed by different capital letters within column are significantly different (p < 0.05), Kruskal-Wallis one way analysis of variance (ANOVA) followed by a Tukey Multiple comparison analysis.

^dValues followed by different capital letters within column are significantly different (p < 0.05), Kruskal-Wallis one way analysis of variance (ANOVA) followed by a Tukey multiple comparison analysis.