Analysis of herbicide residues in sugar beet and sugar J . TEKEL', P. FARKAS, J . KOVACICOVA and A. SZOKOLAY A simple quantitative TLC method for the determination of the residues of herbicide inhibiting photosynthesis was compared with capillary GLC for the analysis of atrazine, chloridazone, lenacil, phenmedipham and desmedipham in sugar beet and sugar. No significant differences in the determination limit and precision of the two methods were found.
Monitoring of herbicide residue levels in commercial sugar revealed low levels of atrazine (0.003 mg . kg-' on average) in all the samples. This contamination level does not present a health hazard for consumers.
A wide range of herbicidal preparations are registered for use in sugar beet. In the CSSR the control of important weeds in sugar beet stands is essentially based on preparations containing chloridazone (4-amino-1-phenyl-5-chloro-pyridazone) and phenmedipham [O-(3-methoxycarbonylanilino)-N-(3'-methylphenyl)-carbamate] and, recently, metamitron (4amino-4,5-dihydro-6-phenyl-3-methyl-l,2,4-triazin-5-one). Several combined preparations with the active substances chloridazone + lenacil (3-cyclohexyl-5,6-trimethylene-uracil) and phenmedipham + desmedipham [3-(ethoxycarbonylanilino)-N-phenylcarbamate)
are also used in agricultural practice. Residues of these compounds can therefore be expected in the crop. Under extensive chemization, the plant products may also become contaminated with the residues of herbicides used in previous years, as has been reported for atrazine [l]. The influence of atrazine residues in soil on sugar beet was studied by FRANK [2] and ZIMDAHL et al. [3]. Maximum residue limits such as [4] were adopted to protect consumers' health from excessive burdening with these and other agricultural chemicals. However, the maximum residue limits (MLR's) apply only to the agricultural product "as it is " i.e. to the sugar beet but not to the sugar made from it. Consistent analytical control of both the agricultural products and the final food items, along with good agricultural practice [ 5 ] , are necessary to keep the contamination within reasonable borders.
Chromatographic methods have the key role in the analysis of herbicide residues. Lenacil residues in sugar beet were analyzed by gas-liquid chromatography (GLC) [6, 71 and residues of chloridazone and its metabolites by capillary GLC IS]. GLC is also widely used for the