Field experiments were conducted on six loam and sandy loam soils to study the influence of various soil parameters on atrazine, cyanazine, alachlor, metolachlor, and pendimethalin efficacy. Herbicidal activity was highly correlated to the soil organic content. Humic matter content was equally or better correlated (r = 0.70 to 0.91) with herbicide bioactivity than was organic matter content (r = 0.66 to 0.84). Regression equations were determined which allow herbicide rate recommendations for 80% weed control to be calculated based on soil humic matter or organic matter levels.

A laboratory study was performed to investigate the relationship between chemical (non‐biological) and microbial degradation of cyanazine and atrazine in soils ranging in pH from 5.3 to 8.1. Atrazine degradation was dominated by chemical processes in both a moderately acidic and a neutral pH soil, but showed a significant microbial involvement in the neutral pH soil. The primary cyanazine degradative mechanism was dependent on soil properties. Cyanazine was short‐lived in neutral to slightly basic soils, due to rapid microbial degradation. Cyanazine amide and cyanazine acid were the major metabolites formed. In a moderately acidic soil, microbial degradation was slowed and chemical processes were the primary means of cyanazine degradation.

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An interlaboratory study was conducted to evaluate a method for determining glycidyl fatty acid esters (GE) in edible oils. Samples were dissolved in tert‐butyl methyl ether/ethyl acetate and subjected to two solid‐phase extraction (SPE) steps. The first SPE step utilized methanol elution from a C18 cartridge, and the second SPE step utilized n‐hexane/ethyl acetate elution from a silica cartridge. The final extract was analyzed using liquid chromatography with a single quadrupole mass spectrometer in selected ion monitoring (SIM) mode. Quantification was performed using external standardization. Eighteen samples (9 oils × 2 blind duplicates) were assayed for glycidyl palmitate, glycidyl stearate, glycidyl oleate, glycidyl linoleate and glycidyl linolenate by 17 collaborating laboratories from seven countries. Sample matrices included palm, olive, corn, soybean and rapeseed oils. Repeatability (RSDr) ranged from 6.85 to 19.88 % and reproducibility (RSDR) ranged from 16.58 to 35.52 % for samples containing greater than 0.5 mg/kg of individual GE. HORRATR values ranged from 0.62 to 14.70 for determination of total GE. The method provides acceptable results for quantification of GE in edible oils.

An LC–MS method using a single quadrupole mass spectrometer was developed for direct analysis of glycidyl esters of fatty acids in vegetable oils. Without any sample clean-up, this method provided acceptable recovery of seven glycidyl esters, comparable results to a previously-published method utilizing two solid-phase extraction steps, and consistent detection parameters after greater than 200 injections without any cleaning operations performed. This method could readily be implemented as a screening assay for glycidyl esters in most oil laboratories.