The 13C/12C isotopic ratios of samples of acetic acid of biogenic origin obtained by fermentation and of synthetic ones produced from petroleum were determined. The biogenic products had a higher 13C content than the synthetic ones. The origin of vinegar can be determined on this basis. Biogenic acetic acid possesses a lower "C content in the methyl than in the carboxyl group. This regularity was not observed for synthetic acetic acid. The ''C distribution within the molecule seems to depend on the type of synthetic process applied.

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It is shown that carbamate pesticides can be determined at the ppm level in different kinds of fruits and vegetables using high pressure liquid chromatography. The lower detection limit corresponding to a signal to noise ratio of three is between 0,025 and 0,25 ppm depending on the type of carbamate and plant material. In all cases it is below the maximum permissible value for pesticide residues. Due to the high separating power of high pressure liquid chromatography a simple sample pretreatment procedure can be used. The carbamates are extracted from the biological sample by dichloromethane and injected directly into the liquid chromatograph after replacing the extraction solvent by the mobile phase. In many cases a definite identification and quantitation of the carbamate is possible with a single chromatographic column. Some plants with a more complex matrix require a two-column operation in which the effluent fraction of the first column containing the pesticide is transferred by column switching to a second column in order to achieve a complete separation. The improved resolution in the two-column operation is caused by the relative enrichment effect of the fractionation and the increased column length.

The applicability of the specific 3H-radioactivity for the distinction of synthetic and biogenic vinegar was tested. The acetic acid was isolated from the vinegar as calcium acetate, and the calcium acetate was combusted at 830 degrees C to CO2 and H2O. The water was measured either after two destillation steps by liquid scintillation counting or after reduction to hydrogen and reaction to ethane in a gas proportional counter. The difference in the 3H-content between the two types of vinegar in Austria is about 80--100 T.U. Since the level of activity is subject to appreciable annual fluctuations a series of synthetic and biogenic comparison samples always has to be included.

The 13C/12C-isotope ratio is characteristic for vinegar of fermentation and synthetic origin respectively and used for their differentiation. The acetic acid was isolated from the vinegar as calcium acetate, the calcium acetate was pyrolysed to CaCO3 and the CO2 was released from the CaCO3 with H3PO4. The CO2 was measured in a mass spectrometer with double collector. The difference in the 13C-content between the two varieties of vinegar is 5 0/00; the accuracy of the measurement is between is 0.5 0/00 and 1 0/00 Therefore, addition of synthetic acetic acid in excess of 15--20% to fermentation vinegar can be detected by this method.