Abstract:
A simple High Performance Liquid Chromatograph (HPLC)
method has been developed to identify benamyl (methyl 1-
(butylcarbamoyl)-2-benzimidazole carbamate) and MBC (methyl
2-benzimidazole carbamat~ residues on apple leaves without
cleanup. Sample leaves are freeze dried in a Mason jar and
residues are then extracted by tumbling them in chloroform
containing 5,000 microgram per milliliter of n-propyl isocyanate
(PIC) at 10 C. To the extract, n-butyl isocyanate
(BIC) was added at 5,000 microgram per milliliter and 20
microliter of this mixture injected onto the HPLC system.
Separation is accomplished by the use of a Brownlee LiChrosorb
silica gel column with a guard column and' operated
with a mixed mobile phase consisting of chloroform and
hexane (4:1) saturated with water. MBC, a degradation product
of benomyl is identified if present as methyl l-(npropyl
carbamoyl)-2-benzimidazole carbamate (MBC-n-PIC).
Both benomyl and MBC-n-PIC can be detected with aKUltraviolet
(UV) detector (280nm) at a concentration as low as
0.2 microgram per milliliter in apple leaves. The fate of
benomyl on apple foliage after spray application of benomyl
(Ben late 50 per cent wettable powder) was investigated by
the method thus described. Benomyl quickly dissipated during
the first 3-7 days, but the dissipatio'n sltowed down
thereafter. In contrast, the concentration of MBC in leaves
gradually increased after repeated applications of Benlate.
