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ARS Home » Research » Publications at this Location » Publication #114904
Title: SOLUBILITY OF TRIAZINE PESTICIDES IN PURE AND MODIFIED WATER FOR SUBCRITICAL WATER EXTRACTION

Author
item Curren, Meredith
item King, Jerry

Submitted to: Analytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The analysis of toxicants such as pesticides in foods and environmental matrices requires a preliminary removal (or extraction) step followed by further processing of the sample before it is ready for analysis. Traditionally, chemical solvents have been used, some of which are toxic and potentially harmful to the environment and laboratory work. In this study, water under high pressure and at elevated temperatures is used as a alternative solvent to the above reagents to solubilize pesticides. The technique makes use of the fact that by pressurizing water at elevated temperatures, one can prevent it from boiling. Hence, the temperature of water can be varied for extractions, which regulates its solvent or removal power for pesticide residues in foodstuffs. In addition, water has been combined with ethyl alcohol as an alternative for solvating pesticides. Adequate solubility of the pesticides has been obtained in the two above media for extraction purposes. This provides analysts working in government and private laboratories with a safer method of extracting pesticide residues from a variety of samples.

Technical Abstract: Solubility measurements in pure and modified water serve as a basis for optimizing the subcritical water extraction of triazine pesticides. The solubilities of the triazine pesticides atrazine, cyanazine, and simazine were measured in pure subcritical water at temperatures ranging from 50 to 125 deg C. The solute solubilities were measured using a static solubility yapparatus with on-line liquid chromatographic (LC) detection. By increasing the temperature of water, the solubility of atrazine was increased 25-fold from its value at 50 deg C, to a concentration of 1770 ug/mL at 125 deg C. The solubility of cyanazine increased an order of magnitude from 50 deg C to a value of 2740 ug/mL at 100 deg C. In contrast, the solubility of simazine only increased to a concentration of 240 ug/mL at 100 deg C because it is less polar. The solubility of atrazine was also measured in ambient and hot water modified with 8 - 42 wt t% ethanol and in hot water modified with 28 wt % urea. At 100 deg C, atrazine solubility was 970 ug/mL in water modified with urea and was as high as 6240 ug/mL in water modified with 20 wt % ethanol. The solubility of atrazine in hot water can therefore be doubted if the water is modified with urea and can be increased over an order of magnitude if ethanol is used as modifier. The data indicate that both increasing the system temperature and adding a cosolvent to the water effect an increase in analyte solubilities.