Alkylenebis-dithiocarbamates

The first xanthates of V(IV), [Cp2V(Rxanth)] (R = Me, Et, Pr , or Bu), isolated as purple solids were prepared by the same method (71). Kwoka et al. (70) were able to obtain an alkylenebis(dithiocarbamate) vanadyl complex, VO[SjjCNH(CH2) NHCS2] for n — 2, but not for... 

Alkylenebis(dithiocarbamates) compounds, known also as ethylenebisdithiocarba-mates (EBDCs), are nonsystemic, low-toxicity pesticides with strong and broad fungicide activity on plant diseases. Developed by Rohm and Haas and E. I. du Pont de Nemours, they are used to protect vegetables and fruit crops. 

The European Community guidelines specify that the maximum residue limit (MRL) for alkylenebis(dithiocarbamates) in fruits and vegetables is 0.05 mg carbon disulfide (CS2)kg ... 

Because of their polymeric forms, alkylenebis(dithiocarbamates) are insoluble in water and most organic solvents. Additionally, they form strong complexes with different metal ions No extraction and chromatographic procedure has been reported for the parent compound of this chemical class. These compounds decompose readily under acidic conditions, for example by contact with the fruit or plant juice generated during sample preparation. 

Two primary types of methods have been developed to determine alkylenebis-(dithiocarbamate) residues in different crops. Both methods are based on the decomposition of the alkylenebis(dithiocarbamates) at elevated temperature in hydrochloric acid and stannous chloride to form carbon disulfide, which is analyzed by either spectrophotometry or gas chromatography (GC). 

For the spectrophotometric method, the evolved carbon disulfide is reacted with copper acetate and diethylamine to form a yellow copper complex which can be measured at 435 nm." The recoveries range between 70 and 90%. Reproducibility of this method was improved by reducing the time and the mode of sample pretreatment. Since all alkylenebis(dithiocarbamates) decompose to carbon disulfide by acid degradation, the above analytical methods are not selective. The result is the measured total residues of all alkylenebis(dithiocarbamates) related products. However, this method is recommended as standard method S15 for alkylenebis(dithiocarbamates) by the German Research Association. ... 

Gel permeation chromatography with UV detection at 285 nm was used for the determination of alkylenebis(dithiocarbamates) containing the original alkylenebis-(dithiocarbamate) moiety on tomatoes and lettuce treated with maneb and zineb. 

The analytical methods specified above, based on the evolution of carbon disulfide from the parent alkylenebis(dithiocarbamates) by hot acid decomposition using spectrophotometry or GC, are accepted as routine methods to determine alkylenebis-(dithiocarbamate) residues. The two methods are described in detail below. 

As the alkylenebis(dithiocarbamates) are not soluble in water or organic solvents, there are two possible procedures to carry out the recovery experiments. The first is to fortify the solid standard onto the untreated sample in the decomposition vessel, and follow the determination procedure as described above. A second option is to... 

The principle of this determination is the same as for the above spectrophotometric methodology. Alkylenebis(dithiocarbamates) are decomposed with hydrochloric acid and stannous chloride in a closed glass headspace flask at elevated temperature. An... 

Alkylenebis(dithiocarbamates) are not stable and decompose on contact with acidic fruit and vegetable juice generated during the sample preparation. The sample preparation is a critical step in their determination. The homogenization should be made with frozen samples as rapidly as possible followed immediately by the analysis. 

The most suitable routine analytical method for the determination of alkylenebis-(dithiocarbamate) residues in fruits and vegetables is hot acid hydrolysis with stannnous chloride and concentrated hydrochloric acid, followed by determination of the evolved carbon disulfide by spectrophotometry or GC. 

Dithiocarbamates and alkylenebis-dithiocarbamates can also be analyzed by GC (142-145). The dithiocarbamates are acid hydrolyzed to carbon disulfide, which is then determined by colorimetry (55) or by headspace GC (27). 

Alkylenebis(dithiocarbamate)s and dimethyldithiocarbamates The pesticides in these groups are also regarded as unspecific SH reagents. Nabam is the disodium salt of alkylenebis(dithiocarbamate) ... 

Maneb or mancozeb. The analysis of alkylenebis(dithiocarbamates) of some bivalent metal ions is hampered by their low solubility, low stability, and polymeric structure (Bardarov and Zaikov 1989). Furthermore, the methods developed for their determination have low selectivity. Indirect methods include spectrophotometric, gas chromatographic (GC), or thin-layer chromatographic (TLC) determinations of the reaction products, liberated after reduction (in an acidic medium) by carbon disulfide (Bardarov and Zaikov... 

Bardarov V and Zaikov C. 1989. Application of high-performance liquid chromatography with spectrophotometric and electrochemical detection to the analysis of alkylenebis(dithiocarbamates) and their metabolites. J Chromatogr 479 97-105. 

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