THE DETERMINATION OF THE HERBICIDE TERBACIL IN ASPARAGUS SPEARS BY GAS-CHROMATOGRAPHY

In a 2-yr study, asparagus spears from established plantings at two sites in British Columbia and one site in Ontario were analyzed for terbacil residues following preemergence and early postemergence applications of terbacil at 0.6, 1.1 and 2.2 kg ha-1. Gas chromatographic determination of terbacil residues using N-specific alkali flame ionization detection indicated that at one site, maximum terbacil residues in the preemergence samples were 14 +/- 3-mu-g kg-1 for the 2.2 kg ha-1 application rate, whereas maximum residues in the early postemergence samples for the 2.2 kg ha-1 application rate were 493 +/- 250-mu-g kg-1 at a second site. Recoveries of terbacil from fortified asparagus tissue were 96 +/- 19%, 87.2 +/- 11.9% and 83.3 +/- 7.8% at 10, 50 and 100-mu-g kg-1, respectively.