Determination at low ppm levels of dithiocarbamate residues in foodstuff by vapour phase-liquid phase microextraction-infrared spectroscopy.

A methodology based on the vapour phase (VP) generation of carbon disulphide from non-volatile dithiocarbamate compounds has been developed for determination of pesticide residues in foodstuff at low ppm levels. The method involves a selective reaction combined with liquid phase microextraction (LPME) and transmission infrared measurements. The use of a home made transmission cell improved the detection limits (LOD) compared to the use of attenuated total reflectance measurements by a factor of approximately 80. Using the most appropriate experimental conditions for the CS(2) generation and LPME preconcentration, the precision of the methodology, expressed as the relative standard deviation (RSD), was of the order of 3.1% and the absolute LOD was 0.3 µg dithiocarbamate, which corresponds to 60-120 µg kg(-1), for a sample mass ranging from 2.5 to 5 g. The usefulness of the methodology has been evidenced by the determination of mancozeb residues in strawberries, lettuce and corn samples at concentrations between 1 and 5 mg kg(-1), where the VP-LPME IR provided results comparable with those obtained by a head space gas chromatography mass spectrometry reference procedure.

Photodegradation and flow-injection determination of dithiocarbamate fungicides in natural water with chemiluminescence detection.

A simple and rapid flow-injection method is reported for the determination of dithiocarbamate fungicides (maneb, nabam and thiram) based on chemiluminescence detection. The method involves the photodegradation of dithiocarbamate fungicides via UV light in an alkaline medium. Photoproducts are then reacted with luminol in the absence of an oxidant. Linear calibration graphs were obtained in the range 0.01 - 4.0 mg L(-1) for maneb and nabam and 0.05 - 1.0 mg L(-1) for thiram with relative standard deviations (n = 4) in the range 1.0 - 2.6%. The detection limits (S/N = 3) of maneb, nabam and thiram were 10, 8.0 and 5.0 ng mL(-1), respectively, with a sample throughput of 100 h(-1). The method was successfully applied to determine these dithiocarbamate fungicides in spiked natural water samples.

Simple and rapid method for the determination of ethylenebisdithiocarbamate fungicides in fruits and vegetables using liquid chromatography with tandem mass spectrometry.

A simple and rapid method for determining ethylenebisdithiocarbamates (EBDCs; mancozeb, maneb, and zineb) in fruits and vegetables is described. EBDCs are transformed into dimethylethylenebisdithiocarbamate (EBDC-dimethyl) by methylation after their decomposition with ethylenediaminetetraacetic acid (EDTA). These processes were performed simultaneously in this method. Dimethyl sulfate was used as the methylation reagent, and acetonitrile extracts obtained from partitioning with anhydrous magnesium sulfate and sodium chloride were subjected to dispersive solid-phase extraction with the primary secondary amine sorbent. Liquid chromatography with tandem mass spectrometry in the positive heated-electrospray ionization mode was used for the determination of EBDC-dimethyl produced from EBDCs. The method was validated at levels of 10, 50, and 100 ng g(-1) maneb as a representative EBDC. The recoveries of the present method were between 71 and 101%. The limits of detection and quantification were 0.24 and 0.8 ng g(-1) maneb, respectively.

Liquid chromatographic analysis of maneb and its main degradation product, ethylenethiouera, in fruit juice.

Ethylenethiourea (ETU), a possible human carcinogen and an antithyroid compound, is the main degradation product of the fungicide, maneb, which is widely used in agriculture. In this study, a rapid and accurate method for the determination of maneb and ETU in various fruit juices (tomato, grape and apple) was developed requiring minimal clean-up of sample extract, no derivatization prior to injection and no specialized LC detectors. Samples were cleaned up using silica and octadecylsilica (C18) cartridges before injection into liquid chromatography (LC) with diode-array detection (DAD). Recoveries ranged between 90 and 101% with relative standard deviations from 0.7 to 3.8%. The limits of determination of maneb and ETU were 0.1 and 0.01 mg l(-1), respectively. The proposed method was used to monitor the presence of maneb and ETU in commercial samples taken from different markets of Istanbul, Turkey. Maneb was found in one tomato juice sample at a concentration of 0.45 mg l(-1) but ETU was below the LOQ. Two tomato juices had no detectable maneb residue but contained ETU at levels of 0.08 and 0.11 mg l-(1).

Development of a high-sensitivity quantitative analytical method for determining polycarbamate by gas chromatography-mass spectrometry incorporating temperature-programmable inlet on-column injection.

A highly sensitive analytical method was developed using GC/MS with temperature-programmable inlet on-column injection (TPI on-column GC/MS) for determining methyl dimethyldithiocarbamate (DMDC-methyl) and dimethyl ethylenebisdithiocarbamate (EBDC-dimethyl), which are methyl derivatives of alkali decomposed polycarbamate. This method makes it possible to quantify 0.3 microg/l of polycarbamate in tap water, which is a 1/100 of the residual target value of 30 microg/l in Japan. Moreover, it now becomes possible to distinguish polycarbamate from other dithiocarbamate pesticides (DTCs) that have similar structures, including ziram and thiram, which only incorporate a DMDC side chain, or manzeb, maneb and zineb, which only incorporate an EBDC side chain, by simultaneously analyzing for DMDC-methyl and EBDC-dimethyl.

Dithiocarbamates residues in Brazilian food and the potential risk for consumers.

Dithiocarbamates are a non-systemic group of pesticides widely used to protect crops from fungal diseases. The current methodology used by monitoring laboratories to determine dithiocarbamates in food involves the analysis of CS(2) generated after hydrolysis of the compound present in the sample. This method does not identify the origin of the CS(2) detected, which may or may not be related to the presence of pesticides leading to a potential overestimation of the dietary dithiocarbamate intake. In this paper, 520 food samples (papaya, banana, apple, strawberry, orange, potato, tomato, rice and dry beans) collected in the local market of the Federal District, Brazil, were analyzed for dithiocarbamate content. Detectable levels (> or =10.10 mg/kg CS(2)) were found in 60.8% of the samples, with the highest levels (up to 3.8 mg/kg) found in strawberry, papaya and banana. No residues were found in rice (polished) and only one dry bean sample had detectable levels of the fungicides. Detectable residues were found in the pulp of banana, papaya (including the seeds) and orange (50-62% of the analyzed samples). An exposure assessment, based on dithiocarbamate levels detected in the food crops analyzed in this study, confirms that the intake of dithiocarbamates through food consumption in the country does not represent a health risk to consumers, i.e., the estimated daily intake is less than the acceptable daily intake. Furthermore, the implementation of more selective methodologies to individually analyze these compounds in food monitoring programs in Brazil is not necessary.

Determination of dithiocarbamate fungicide residues in food by a spectrophotometric method using a vertical disulfide reaction system.

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 CS(2). 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 CS(2), 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 CS(2) 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, tomato, cucumber, and potato ranged from 82 to 120%, with relative standard deviations from 0 to 10% (n = 3 or 5). Analysis of apple, tomato, and papaya samples with field-incurred dithiocarbamate residues showed comparable results using both the traditional and the new reaction systems.

Determination of ETU in tomatoes and tomato products by HPLC-PDA: evaluation of cleanup procedures.

An HPLC-PDA method for the determination of ethylenethiourea (ETU), the main degradation product of the organic fungicides ethylene bis(dithiocarbamate)s (EBDCs), in tomatoes and tomato products is reported. Solid-matrix liquid-liquid (l-l) partitioning and separatory funnel l-l partitioning for the cleanup were examined. The effect of salt addition, pH, and phase ratio on analyte recovery at the cleanup step was studied. It was found that solid-matrix l-l partitioning afforded higher precision and more selective separation of the analyte. According to the method proposed, the samples were extracted with methanol/water (3:1, v/v) and cleaned up on an Extrelut 20 column. ETU was eluted with dichloromethane and separated on a reversed phase HPLC column. For tomato products with degrees Brix > 20 further purification through silica cartridge was adopted. The method was validated over the following ranges of concentrations: 0.01-0.5 mg/kg for tomatoes, 0.01-0.1 mg/kg for tomato juice, and 0.05-0.25 mg/kg for tomato paste. The accuracy (recoveries > 70%) and the precision obtained (%RSD < 10%) were satisfactory.

Risk assessment of dithiocarbamate accelerator residues in latex-based medical devices: genotoxicity considerations.

The Medical Devices Agency (MDA) has investigated potential human health hazards arising from the presence of dithiocarbamate vulcanization accelerators in latex products (mainly gloves). After collection of manufacturer's data on usage and residues of these accelerators, an independent investigation of solvent extractable residues and dithiocarbamate migration into aqueous simulants was commissioned, to complement equivalent "in-house" test data from two major manufacturers. The presence of extractable accelerator residues in commercial products was confirmed. Potential human health hazards associated with dithiocarbamates include genotoxicity and possible carcinogenicity: a review of published data was conducted to evaluate the evidence for this, with particular reference to three zinc dithiocarbamates with significant commercial usage (ZDMC, ZDEC and ZDBC: see Fig. 1). Data gaps were identified, and mutagenicity studies commissioned to fill these. These studies comprised tests both in vitro (bacterial and L5178Y cell gene mutation, cultured lymphocyte chromosome aberration) and in vivo (mouse bone marrow micronucleus, rat liver UDS). It is concluded that ZDMC must be considered a genotoxin (and thus a probable carcinogen): residues of this substance in latex medical devices should be minimized. ZDEC proved genotoxic in vitro but was not clearly genotoxic in vivo, and may have activity intermediate between that of ZDMC and that of ZDBC, which showed at most weak activity in a single in vitro (chromosome aberration) test. It is proposed that the use of ZDBC as a vulcanization accelerator in the manufacture of latex gloves, rather than ZDEC, ZDMC or their precursors, would reduce or remove the health concerns arising from accelerator residues.

Headspace gas-liquid chromatographic determination of dithiocarbamate residues in fruits and vegetables with confirmation by conversion to ethylenethiourea.

Ethylene-bis-dithiocarbamate (EBDC) residues were determined as carbon disulfide (CS2) by an improved headspace gas-liquid chromatographic (GLC) procedure. Among 837 samples of 30 agricultural commodities tested, 43% contained residues above the detection limit for the method: 100% of broccoli samples; 80% of cabbage, kiwifruit, and grape samples; and 71% of cucumber samples. Most of the residues in kiwifruit were on or near the skin. Elimination of false-positive detections by the improved method was confirmed with kiwifruit in 2 independent procedures. Whole fruits were washed with 5% EDTA to remove surface residues of EBDC. Analysis of washes for CS2 by the headspace procedure after treatment with acidic stannous chloride and for ethylene thiourea by LC after prolonged treatment at 60 degrees C qualitatively identified the EDTA-soluble residues as EBDC. Although the improved method does not produce false-positive results, peak area responses of CS2 and the internal standard, thiophene, are influenced by chemical composition of the matrix. With matrixes high in sugar or lipids, the apparent CS2 content may be overestimated by 4-fold. Accurate determination of EBDC residues in these sample types requires appropriate adjustments to matrixes.

Gas chromatography-mass spectrometry determination of ethylenethiourea hemoglobin adducts: a possible indicator of exposure to ethylene bis dithiocarbamate pesticides.

Ethylenebisdithiocarbamates (EBDC) are an important class of fungicides used to control crop diseases and prevent mold. Ethylenethiourea (ETU), reported to be their main degradation and metabolic product in animals and man, may have teratogenic and carcinogenic properties. The feasibility of monitoring exposure to ETU on the basis of the formation of adducts to hemoglobin (Hb) was investigated. Rats given a single oral dose of ETU (from 62.5 to 500 mg/kg body wt) formed stable covalent ETU-Hb adducts. Mild acid hydrolysis of the protein regenerated ETU, allowing its detection by isotope dilution gas chromatography-mass spectrometry (GC-MS). The amount of released ETU increased with the dose. The dose-response curve fitted a linear model only between 62.5 mg/kg and 250 mg/kg. Acid-releasable ETU was also positively identified in the hemoglobin of workers exposed to Mancozeb, an EBDC formulation. In the exposed group, 40% had ETU-Hb adducts levels ranging from 0.5 to 1.42 pmol ETU/mg Hb. Such adducts might be useful for measuring EBDC exposure in humans.

Blood concentrations of carbon disulphide in dithiocarbamate exposure and in the general population.

Blood carbon disulphide (CS2), both free and total, was determined by gas chromatography-mass spectrometry in 112 "normal" subjects and in 20 subjects employed in a dithiocarbamate factory, comprising ten blue-collar workers involved in dithiocarbamate production and ten white-collar office staff. The ten production workers were examined over two workshifts, the first at the beginning of the week (Monday) and the second after an intervening period of at least 1 day. Three blood samples were taken for each shift studied, one prior to starting work, one at the end of the shift and the third 16 h after the end of the shift (on the following morning). The mean CS2 blood levels measured in the 112 normal subjects was 663 ng/l for the free fraction and 3178 ng/l for the total. In 16 blood samples taken from the ten dithiocarbamate factory office workers, the mean free and total CS2 blood levels were 846 and 4140 ng/l, respectively, i.e. not significantly different from those observed in the normal subjects. At the end of the first 8-h shift, the ten dithiocarbamate factory production workers had free and total CS2 values of 1070 and 8471 ng/l, respectively, which were significantly higher than those observed prior to starting work (240 and 4738 ng/l). All the total CS2 levels measured in the shop-floor workers, with the sole exception of the values recorded prior to the start of the Monday shift (4738 ng/l), ranged from 7047 to 8471 ng/l and were significantly higher than those measured in the white-collar staff (4140 ng/l).

Dithiocarbamate residues found on vegetables and fruit marketed in the State of Rio de Janeiro, Brazil

Foram recolhidas 466 amostras de 30 diferentes espécies de hortaliças e frutas destinadas à comercializaçäo, a fim de se determinar o teor de resíduos de fungicidas ditiocarbamatos (Mancozeb, Maneb, Propineb, Tiram e Zineb). As amostras foram coletadas junto a fontes produtoras, em uma regiäo tipicamente agrícola do Estado do Rio de Janeiro. Para as determinaçöes analíticas foi utilizado um método baseado na reaçäo colorimétrica do dissulfeto de carbono liberado pela hidrólise ácida dos fungicidas. Do total de amostras analisadas, 63% apresentaram resíduos, sendo que 24% dessas continham níveis acima dos toleráveis pela legislaçäo vigente. Dentre as 30 culturas analisadas, as hortaliças folhosas apresentaram maior incidência de contaminaçäo (70-100%). A alface e a salsa apareceram como as culturas mais afetadas, com níveis de resíduos superiores a 50% dos limites de tolerância, seguidas pela cenoura (47,4%) e tomate (38,2%). A batata-doce e o nabo näo apresentaram resíduos. É importante o monitoramento de resíduos de ditiocarbamatos, pois apesar de apresentarem baixa toxicidade, podem ser precursores de etilenotiuréia, substância de açäo cancerígena mutagênica e teratogênica

Determination of nabam fungicide in crops by liquid chromatography with postcolumn reaction detection.

The ethylenebisdithiocarbamate (EBDC) fungicide, nabam, was determined in several crop matrixes using liquid chromatography with postcolumn reaction detection. After separation by micellar liquid chromatography, nabam (EBDC sodium salt) was acid hydrolyzed to ethylenediamine and fluorigenically labeled with o-phthalaldehyde-mercaptoethanol (OPA-MERC). Standard curves were linear from the detection limit of ca 1 ng to 1000 ng. Nabam was recovered in high yield (89 plus or minus 7.7%) over a range of concentrations (0.1 to 20 ppm) from fortified samples of papaya, lettuce, cucumber, spinach, and applesauce using a simple extraction method. Efforts to convert the more popular EBDC fungicides, maneb and mancozeb, to nabam are discussed.

Ethylenethiourea (ETU) in relation to use of ethylenebisdithiocarbamate (EBDC) fungicides.

Degradation of ethylenebisdithiocarbamate fungicides (EBDCs) is known to produce ethylenethiourea (ETU). This article reviews the literature available on the toxicology of EBDCs and ETU, the sources in plants and persistence of ETU, and its formation during heat treatment of plant products. Detoxification techniques developed are mentioned, and Maximum Residue Limits and the results of monitoring studies are given for several countries. Some aspects of the methods of analysis are discussed. Although EBDCs have in the past been regarded as relatively harmless, data on their subchronic and chronic toxicity indicate that these toxicological features should not be ignored. ETU has low acute toxicity but possesses carcinogenic, goiterogenic, teratogenic, and mutagenic activity in animal tests. The most prominent aspect of its toxicology is its action on the thyroid gland, which causes hyperplasia and a decrease in thyroid hormone levels. It is a potent teratogen in pregnant rats after either acute exposure or administration throughout organogenesis, inducing a wide spectrum of malformations to the progeny. The teratogenic potential is specific to rat, whereas administration to pregnant mouse, hamster, guinea pig, and cat causes limited or no teratogenicity, except at very high dose levels. The mutagenicity of ETU has not been clearly established, although some data exist that indicate that it indeed has mutagenic potential. ETU can react with nitrites to form N-nitroso-ETU, which is a mutagenic and teratogenic compound. Most of the ETU present in fresh agricultural products treated with EBDCs arises from the presence of ETU in formulations. Surface deposits of EBDCs on plants may be a secondary source. ETU may also be taken up by plants from the soil following the breakdown of EBDCs, but conflicting results have been obtained on this phenomenon. ETU on plant surfaces undergoes subsequent degradation. Although small amounts may persist up to 30 d after spraying, there is no indication that it accumulates in plants. Initial findings that ETU is formed during the heat processing of EBDC-treated foods are confirmed by the more recent literature. However, the variability of the results indicates a wide range of conversion due to processing. Boiling of spinach, pears, grapes, tomatoes, and wheat, treated with different EBDCs, resulted in 3-30% conversion to ETU. Apple juice, dried pomace, and applesauce contained more ETU than the EBDC-treated apples, from which these products were produced. This was also true for tomato juice and canned whole tomatoes. ETU may be produced in the smoke of tobacco containing high EBDC residues.(ABSTRACT TRUNCATED AT 400 WORDS)

Survey of ethylenethiourea (ETU) in ethylenebis(dithiocarbamate) (EBDC) fungicides.

Ethylenethiourea (ETU) has been recognized as a compound with adverse toxicological properties. It may occur in ethylenebis(dithiocarbamate) (EBDC) fungicides as a by-product and/or a degradation product. Restrictions have been issued by the Italian Health Authority to keep the level of ETU in EBDC formulations under 0.5% (on an EBDC technical product basis). A survey was carried out on 85 samples of commercial formulations from the Italian market to verify compliance with the above limitation. ETU was extracted by methanol and determined by gas chromatography with a flame ionization detector. Three of the 85 samples (3.5%) exceeded the limit of 0.5% established by the Italian legislation for ETU.

Residues of EBDC fungicides and ETU in experimental and commercial beverages (beer and wine).

Residues of EBDC (ethylenebisdithiocarbamate) fungicides and ETU (ethylenethiourea; 2-imidazolidinethione) were monitored in beers and wines from different locations. No EBDC residues were detected in any of the samples examined. Concerning the ETU residues, the residue levels higher than the limit of method detection (0.01 ppm) were 22.6% and 7.3% in the commercial beer and wine samples respectively, but the number of samples containing more than 0.1 ppm of ETU was practically negligeable.

The fate of ethylenebis(dithiocarbamate) fungicides during processing of contaminated apples.

A spectrophotometric method based on the liberation of carbon disulfide is suitable for the determination of ethylenebis(dithiocarbamate) (EBDC) residues on apples. Homogenization of samples before analysis initiates rapid breakdown of EBDC, resulting in low recoveries. Thermal conversion of mancozeb to ethylenethiourea (ETU) in the course of apple processing was investigated. The formation of ETU from EBDC could be reduced by lowering the pH value. The presence of an antioxidant (ascorbic acid or cysteine) significantly diminished the yields of ETU after heating, but they inhibited its subsequent decomposition. The rate of ETU formation did not correspond to a relatively rapid disappearance of the parent compound. The levels of ETU residues in the canned baby food originating from contaminated apples were evaluated after a 9-months storage period: the reduction of ETU amounts varied from 26 to 70%.