Bull. Spec. CORESTA Symposium, Kallithea, 1990, p. 226, S20, ISSN.0525-6240

Determination of free and glycosidically bound maleic hydrazide in tobacco

Philip Morris Europe, R&D, Neuchatel, Switzerland.
Maleic hydrazide (3,6-dioxo-1,2-dihydropyridazine) (MH), a systematic plant growth regulator, is used extensively for tobacco sucker control. Since a maximum amount of 80 ppm MH in cigarettes is recommended in Germany and individual values on raw leaf tobacco up to 300 ppm were found, a procedure is needed to perform a routine control of MH in tobacco leaves and filler. Currently the determination of MH is performed according to ISO 4876. As this method is time consuming and difficult to handle investigations for an easier and more efficient method have been carried out. During these investigations a gas chromatographic method was developed for the determination of free as well as glycosidically bound MH on tobacco. MH is converted with dimethyl sulfate to its N-O dimethyl derivative and analysed by gas chromatography using a specific N-P detector. MH can exist in 3 tautomeric forms; the derivatization with dimethyl sulfate, however, gives only one isomer i.e. 2-met hyl-6-methoxy-3-oxo-pyridazine which corresponds to the predominant tautomer. The method has been applied to cigarette filler and ground tobacco leaves. Free MH residues were determined directly in aqueous tobacco extracts whereas total MH values were measurd after acid hydrolysis. Recoveries of free MH added to aqueous tobacco extracts averaged 90% at 20ppm. A relative standard deviation of 7% was obtained at both 10 and 70 ppm on tobacco samples. The detection limit of the method determined on cigarette filler was 5ppm. At present up to 20 samples can be handled per day by the GC method.