False positive effect of sulfur sources used in growing and processing of vine (Vitis Vinifera L.) leaves on the results of dithiocarbamate analysis based on carbon disulfide measurement

Vine leaves, which are produced fresh, brined or fermented from the leaves of Vitis Vinifera in Türkiye are an important food. Sulfur is used as a pesticide and sulfur compounds can be used as additives during the growing and processing of the vine leaves. These sulfur sources cause positive results on carbon disulfide (CS₂) measurements by GC-MS. Therefore, the main objective of the present study was to investigate the effects of residues of sulfur or sulfur compounds on dithiocarbamate analysis methods based on CS₂ measurement. For this, vine leaves were produced by controlled agricultural production and processed as brine under controlled conditions. The sulfur dioxide (SO₂) and dithiocarbamate analysis were carried out on the vine leave obtained by applying sulfur spraying in agricultural treatments and brined vine leaves produced by adding sodium metabisulfite (SM), and control samples of each stage. SO₂ was not detected in any of the samples in this study. SO₂ residues did not occur in the vine leaves as a result of the sulfur spraying application and therefore did not have a false positive effect on dithiocarbamate analysis. However, approximately 0.15 mg kg^-1 false positive dithiocarbamate was detected, which is thought to originate from natural sulfur in the vine leaves. The effect of SM, which was used in low concentration in the production of brined vine leaves, on dithiocarbamate results was limited. Even if SM was not used, the total false positive dithiocarbamate result in the brined vine leaves production process was approximately determined as 0.20 mg kg^-1. This study showed that the dithiocarbamates analysis method based on CS₂ measurement may lead to false positive results in brined vine leaves since sulfur compounds are found naturally in vine leaves.