Selective determination of thiram residues in fruit and vegetables by hydrophilic interaction LC-MS.
Thiram belongs to the most important class of dithiocarbamate (DTC) fungicides including dimethyldithiocarbamates (DMDs), ethylenebis(dithiocarbamtes) (EBDs) and propylenebis(dithiocarbamates) (PBDs). During the surface extraction of fruit and vegetables for the LC-MS determination of residues of DMDs, EBDs and PBDs, thiram is reduced by the penicillamine buffer to the DMD anion, thus resulting in false-positive findings of DMD fungicides like ziram. Therefore, an alkaline sulfite buffer was applied for surface extraction, quantitatively transforming thiram into the DMD anion and a stable DMD-sulfite adduct that was used as a selective marker for thiram. Separation was performed isocratically on a ZIC-pHILIC column with acetonitrile-10 mM ammonium hydroxide solution (85/15). Mass selective detection was carried out on a single-quadrupole mass spectrometer coupled to an electrospray ionisation interface operating in negative mode. Using d12-thiram as the internal standard, recoveries of 80-108% were obtained from apples, tomatoes, grapes and sweet peppers, spiked in the range of 0.02-1 mg kg(-1). Limits of detection and quantification were 0.6 and 2 µg kg(-1), respectively.
a Institute of Food Chemistry , University of Hohenheim , Stuttgart , Germany.
Daniela
D
Ringli
Wolfgang
W
Schwack
D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004355:Drug Stability; D005506:Food Contamination / Q000032:analysis; D005638:Fruit / Q000737:chemistry*; D005659:Fungicides, Industrial / Q000032:analysis*; D057927:Hydrophobic and Hydrophilic Interactions; D013058:Mass Spectrometry / Q000379:methods*; D010573:Pesticide Residues / Q000032:analysis; D012997:Solvents; D013447:Sulfites; D013893:Thiram / Q000032:analysis*; D014675:Vegetables / Q000737:chemistry*; D015039:Ziram / Q000032:analysis / Q000737:chemistry
D005659:Fungicides, Industrial; D010573:Pesticide Residues; D012997:Solvents; D013447:Sulfites; D013893:Thiram; D015039:Ziram