Residues of chlormequat and mepiquat in grain--results from the Danish National Pesticide Survey.

The objective of the present work was to establish information on chlormequat and mepiquat residues in grain for human consumption. Chlormequat (2-chloro-N,N,N-trimethylethylammonium, CAS RN 7003-89-6) and mepiquat (1,1-dimethylpiperidinium, CAS RN 15302-91-7) are plant growth regulators used to stabilize stalks in cereals. The study was part of the Danish National Pesticide Survey, managed by the Danish Veterinary and Food Administration. Samples were collected in autumn 1997. Residue contents were determined with a newly developed liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for chlormequat analysis. The method was extended to include mepiquat in the present study. Quantitation was done by the internal standards method, using mass chromatograms of the most intense daughter ions of mepiquat (m/z 98), chlormequat (m/z 58), and [13C]-chlormequat (m/z 61, internal standard). For chlormequat, the overall limit of detection (LD) was 6 micrograms/kg and the limit of determination (LOD) was 10 micrograms/kg. For mepiquat, LD was 2 micrograms/kg and LOD was 3 micrograms/kg. Of 77 samples analyzed, 51 contained chlormequat and 11 contained mepiquat. The highest levels of chlormequat were found in samples of oatmeal (3.76 mg/kg) and rye (1.08 mg/kg). In 9 rye grain samples containing chlormequat, 5 also contained mepiquat. However, in all samples analyzed, the residues of chlormequat and mepiquat were below maximum residue limits.