A method for derivatizing carboxylic acid herbicides with 2,2,2-trifluoroethanol (TFE) in preparation for gas chromatographic (GC) analysis was developed. Esterification efficiency was determined by GC with electron capture detection (ECD), and esters were identified by GC with mass-selective detection (MSD). On the basis of reaction temperature for optimum esterification efficiency, 13 common carboxylic acid herbicides were separated into 2 groups before reaction with TFE. TFE derivatization was optimized for simultaneous analyses by altering reaction temperature, re action time, and concentration of sulfuric acid in reaction solutions. The method is simple, safe, and economical, and it gives good resolution without a laborious cleanup. Recovery of 13 analytes from water, taken from a pesticide residue well, was greater than 80% for all except 2 analytes. The well-water was fortified with analytes at the lower microgram-per-liter concentrations required for detection of pesticide residues in potable water systems. The method can simultaneously determine multiple herbicide residues in water samples with a high degree of accuracy and precision.

A procedure is described for the extraction of dithiopyr [2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridine dicarbothioic acid, S,S-di methyl ester] from soil leachate and its analysis by isothermal electron-capture gas chromatography while using metribuzin [4-amino-6-(1,1-dimethylethyl)-1,2,4-triazin-5(4H)-one] as an internal standard during quantitation. Dithiopyr extraction from aqueous soil leachate by liquid-liquid extraction (LLE) with hexane, toluene, or ethyl acetate was compared with solid-phase extraction (SPE) using an LC-18 SPE tube. The influence of silanizing the glassware on dithiopyr recovery was tested. The LLE methods yielded approximately 56% recovery of dithiopyr from the aqueous solution. SPE with silanized glassware resulted in the highest dithiopyr recovery. This system yielded recovery levels near 99% dithiopyr from aqueous-solution volumes ranging from 4 to 80 mL, with the volumes containing dithiopyr concentrations ranging from 1 to 100 µg/L. The SPE soil-leachate samples were void of compounds that interfered with the gas chromatography of metribuzin and dithiopyr, and the electron-capture detector responded linearly to dithiopyr, in toluene, over a concentration range of 0.4 to 150 µg/L.

EPTC (S-ethyl dipropylthiocarbamate) (33μM) and diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] (90μM) inhibited the incorporation of 6 mM acetate-2-14C (Ac∗) by 80% and 65%, respectively, and the incorporation of 0.5μM malonate-2-14C (Mal∗) by 32% and 26%, respectively, into the lipids of spinach (Spinacia oleraceaL.) chloroplasts. The inhibition of Ac∗or Mal∗incorporation into lipids was not observed in the presence of excess Ac∗or Mal∗, respectively. Incorporation of palmitate-1-14C and oleate-1-14C into chloroplast lipids was inhibited by EPTC and diallate. Mal∗incorporation into dienoic fatty acids was inhibited by EPTC and diallate. The concentration of EPTC and diallate inhibiting lipid synthesis falls into the physiological range of these herbicides, explains some metabolic effects of these compounds, and fits as the mode of activity of these herbicides.