Gas-Liquid and Liquid Chromatographic Determination of Zineb and Maneb for the Assessment of Occupational Exposure in the Production of Ornamentals

Abstract

Health hazard surveys have been conducted on Dutch bulb farms and in greenhouses used for cultivation of carnations in order to determine occupational exposure to the fungicides zineb and maneb. Occupational exposure is estimated by determining inhalatory and dermal exposure. Inhalatory exposure is measured by personal air sampling and dermal exposure by measuring maneb or zineb on cotton gloves worn by the workers. Also, foliar dislodgable residues of zineb on carnation leaves are determined. For determination of exposure to maneb and zineb on bulb farms, a gas chromatographic method is used. The ethylene-bisdithiocarbamates on cotton gloves are converted into their soluble sodium form with ethylenedinitrotetraacetic acid (EDTA) and subsequently hydrolyzed to form carbon disulfide. Zineb and maneb on air sampler filters are directly hydrolyzed. The carbon disulfide is determined by headspace gas chromatography using an electron capture detector. Because of interference by the pesticide thiram in the carnation culture, a high-performance liquid chromatography (HPLC) method has been developed in which the ethylenebisdithiocarbamates can be separated from thiram. This method comprises solubilization of the ethylenebisdithiocarbamates in EDTA, extractive methylation, and subsequent HPLC using UV detection at 272 nm. Validation of the methods has been carried out with respect to analytical recovery and stability of zineb and maneb. Both methods appear to be suitable for the determination of occupational exposure to the ethylenebisdithiocarbamates zineb and maneb, the gas chromatographic method having the lower detection limit (0.02 mg/L versus 0.1 mg/L of zineb or maneb in EDTA solution) and the HPLC method offering better specificity with respect to other dithiocarbamates such as thiram.