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N‐Nitrosodimethylamine (NDMA) levels in samples of 600 g litre−1 aqueous dimethylamine (DMA) solution stored at 4, 25 and 40°C, in formulations of the DMA salt of 2, 4‐dichlorophenoxyacetic acid (2, 4‐D) and of the DMA salt of 4‐chloro‐2‐methylphenoxyacetic acid (MCPA) at 40°C were monitored using a gas‐liquid chromatograph coupled with a thermal energy analyser (g.l.c./t.e.a.). The NDMA content of aqueous DMA at 4°C increased from 0.32μgg−1 to 8.6μgg−1 in 156 days. At 25°C it increased from 0.20μgg−1 to 10.5 μgg−1 in 156 days and at 40°C from 0.76μgg−1 to 7.12μgg−1 in 54 h. At 40°C, the NDMA in the 2, 4‐D/DMAsalt increased from 0–53μgg−1 to 2.79μgg−1 in 96 days and in the MCPA/DMA salt from 0.48μgg−1 to 5.51 μgg−1 in 21 days.

A simple and rapid analytical method has been developed for the determination of JV-nitrosodimethylamine (NDMA) in amine salts of phenoxy herbicide formulations of 2,4-D and MCPA, plus mixtures of these with mecoprop and dicamba amine salts. Sample preparation consists of direct extraction using pre-packed disposable extraction tubes eluted with dichloromethane followed by cleanup on a disposable silica gel mini-column using ethyl acetate as eluting solvent. Samples are injected on-column for gas chromatography with a Megabore fused silica column; the NDMA is measured by a thermionic specific detector (TSD) that is selective for nitrogen-phosphorus (NP). A detection limit of 0.1 μg/mL was easily attainable without any concentration step because the solvent volume is minimal. TSD and thermal energy analyzer (TEA) results have been compared and confirmed by gas chromatography/mass spectrometry. Recovery studies were performed as well as a reproducibility study on one of the 2,4-D formulations.

A rapid and simple method to isolate and determine JV-nitrosodimethylamine (NDMA) in formulations of ferbam or dibam has been developed. Depending on the type of formulation, the sample is extracted or diluted with water which is subsequently extracted with dichloromethane. NDMA is isolated by passing the organic fraction through a silica gel column and eluting the column with acetone. The acetone eluate is analyzed directly for NDMA by using a gas chromatograph connected to a thermal energy analyzer detector (GC/ TEA). The limit of detection (LOD) is 40 pg (0.04 ppm) and the limit of quantitation (LOQ) is 100 pg (0.1 ppm). The recovery range for this method is 85-112% for ferbam spiked at 0.33-0.75 ppm, and 91- 113% for dibam spiked at 0.32-1.09 ppm. Sixteen commercial samples of ferbam and 4 of dibam were analyzed; one ferbam sample contained 19.8 ppm NDMA while all others contained less than 1 ppm. Chem-Elut extraction tubes were found to generate trace quantities of nitrosamine from samples containing amine. If amine is absent, an extraction tube could be used in place of dichloromethane extraction to give similar values in recovery range, LOD, and LOQ.