George E Keppel

Bio: George E Keppel is an academic researcher from Food and Drug Administration. The author has contributed to research in topics: Dithiocarbamate & Thiram. The author has an hindex of 3, co-authored 5 publications receiving 103 citations.

Cigarettes as a source of some trace and heavy metals and pesticides in man

Abstract: Trace and heavy metal and pesticide contents of different tobacco brands sold in Finland during 1920 to 1984 were determined by atomic absorption spectroscopy and gas chromatography-mass spectrometry with the purpose of investigating the variation in contents over time. In addition, the following were studied: the effect of commercial filters in cigarettes in preventing the inhalation of metals, the transfer of metals and pesticides to the mainstream smoke; and the correlation between the cadmium content of adipose tissue of smokers and their smoking habits. No differences were found in trace and heavy metal contents of different brands and packs from different decades. The pesticide residues in tobacco have followed the pattern of their use in the tobacco plantation. The dichlorodiphenyltrichloroethane (DDT) content of tobacco has decreased during the past 20 yr to about 1/200 of the peak value, i.e., from 34.5 to 0.17 micrograms/g. Cigarette filters significantly prevent the inhalation of cadmium, lead, magnesium, and iron. The mean content of cadmium in fat tissue of male smokers was four times that of non-smokers. The difference was statistically significant.

Determination of Dithiocarbamate Fungicide Residues in Food by a Spectrophotometric Method Using a Vertical Disulfide Reaction System

Abstract: Dithiocarbamates are a class of fungicides extensively used in many crops worldwide. The current residue definition of dithiocarbamates in food for compliance with maximum residue limits, at national and international levels, is total residues arising from the use of any or each dithiocarbamate fungicide, determined as CS2. The analytical method most frequently used to analyze dithiocarbamate residues in food for monitoring purposes was proposed more than 30 years ago. In this method, total dithiocarbamates are decomposed to CS2, which is purified and reacted with a cupric reagent. The yellow complex formed is quantified by spectrophotometry. In this paper, a new reaction system for the purification and complexation of CS2 is proposed. The new system is less fragile than the traditional design, is easier to assemble, and allows for a higher sample throughput, in addition to being of low cost. Recovery of added mancozeb, thiram, or ziram (0.15−8.0 mg/kg) in rice, beans, apple, banana, orange, papaya, tomat...

Monitoring of pesticide residues in Egyptian fruits and vegetables during 1997.

Abstract: A total of 2318 domestic samples of different types of fruits and vegetables were collected from eight Egyptian local markets in six different regions of the country. All samples were examined for residues of 54 pesticides, including organophosphorus, organonitrogen, organohalogen and certain pyrethroides. However, dithiocarbamates were analysed in only 318 samples. Overall, 81.5% of the samples had no detectable pesticide residues. Of the contaminated samples, 18.5% contained detectable residues and 1.9% exceeded their maximum residue limits (MRLs). Root and leafy vegetables showed the lowest contamination rates (1.9 and 4.7%, respectively), slightly exceeding the MRLs in leafy vegetables. However, fruit samples showed a slightly higher proportion of contamination than vegetables (29 and 14.3%, respectively). Fruit also exhibited a higher level of violation than vegetables (2.3 and 1.9%, respectively). The contamination and violation rates were lower than the percentages recorded in previous years' monitoring studies. Dicofol and dimethoate were the most frequently occurring pesticide residues at 5.1 and 5.0%, respectively. Dimethoate showed higher violation levels (0.69%). However, dicofol showed a slight violation rate (0.09%) which indicates good agricultural practices for dicofol use. Dithiocarbamates residues were found in 21 of the 318 samples analysed, which when expressed as a percentage contamination was 6.6%, and only one sample exceeded the MRL.