Field Screening Method for Above-Tolerance Residues of Dithiocarbamate Fungicides

1982 ◽  
Vol 65 (4) ◽  
pp. 909-912
Author(s):  
Daniel E Ott ◽  
Francis A Gunther
Keyword(s):  
Elevated Temperature ◽  
Carbon Disulfide ◽  
Fruits And Vegetables ◽  
Stannous Chloride ◽  
Screening Method ◽  
Reaction Flask ◽  
Single Test ◽  
Field Screening ◽  
Tolerance Level ◽  
Headspace Gas

Abstract A field screening method has been developed for detecting above-tolerance residues of dithiocarbamate (DTC) fungicides on fruits and vegetables. A harvested crop might be condemned as unfit for market if above-tolerance DTC residues are present; however, by using this screening method, a grower might be able to postpone harvesting a crop until the screening test indicates that residues have dissipated below the tolerance level. The method depends on carbon disulfide generated from DTC fungicides at an elevated temperature into the headspace gas above the contents of a septum-sealed reaction flask, with hydrochloric acid and stannous chloride present. The syringe-withdrawn, headspace carbon disulfide then reacts with the appropriate chromophore reagent already in the syringe. The lower limit of detectability is about 2 ppm DTC fungicide from 30 g chopped crop. A single test can be completed in about 90 min; the average time per test when several are conducted sequentially is considerably shorter.

Colorimetric Method for Field-Screening Above-Tolerance Parathion Residues on and in Citrus Fruits

1983 ◽  
Vol 66 (1) ◽  
pp. 108-110
Author(s):  
Daniel E Ott ◽  
Francis A Gunther
Keyword(s):  
Screening Method ◽  
Colorimetric Method ◽  
Navel Orange ◽  
Citrus Fruits ◽  
Single Test ◽  
Field Screening ◽  
Tolerance Level ◽  
Preliminary Work ◽  
Reaction Solution ◽  
Analytical System

Abstract A colorimetric technique has been developed which is suitable for use as a field-screening method for detecting above-tolerance levels of parathion on and in citrus fruits. By using this method, a grower should be able to postpone harvesting a crop until parathion residues are below tolerance level, so that the crop is safe to market. The method depends on the reaction of parathion with 4-(p-nitrobenzyl)- pyridine. Parathion is extracted by mixing chopped citrus rind with acetone in a hand-operated homogenizer. The extract is partially cleaned by a partitioning step before final cleanup with a Sep-Pak Florisil cartridge. The colored reaction solution is read at 560 nm by using a portable, rechargeable spectrophotometer. A single test can be completed in about 75 min; the average time per test when several are conducted sequentially is considerably shorter. The analytical system responds readily to <5 ppm parathion on or in 1 g navel orange rind, which corresponds to <1 ppm in the whole fruit. The present U.S. tolerance for parathion on or in citrus is 1 ppm on a whole fruit basis. Preliminary work indicates that the method should also be suitable for apples.

Rapid field-screening method for PCBs

1993 ◽  
Author(s):  
Tuan Vo-Dinh ◽  
Wendi Watts ◽  
Gordon H. Miller ◽  
A. Pal ◽  
DeLyle Eastwood ◽  
...  
Keyword(s):  
Screening Method ◽  
Field Screening

A Field Screening Method for Contaminated Sites

1997 ◽  
pp. 189-192 ◽  
Author(s):  
K. Ebert ◽  
P. M. Krämer ◽  
A. A. Kettrup
Keyword(s):  
Screening Method ◽  
Contaminated Sites ◽  
Field Screening

Modification of the Carbon Disulfide Evolution Method for Dithiocarbamate Residues

1969 ◽  
Vol 52 (1) ◽  
pp. 162-167 ◽  
Author(s):  
George E Keppel
Keyword(s):  
Hydrogen Sulfide ◽  
Hydrochloric Acid ◽  
Carbon Disulfide ◽  
Lead Acetate ◽  
Stannous Chloride ◽  
Acetate Solution ◽  
Colorimetric Measurement ◽  
Fungicide Residues ◽  
Mineral Acids ◽  
Lead Acetate Solution

Abstract A study was made of the analytical method for dithiocarbamate fungicide residues based on decomposition by hot mineral acids to the amine and carbon disulfide and colorimetric measurement of the carbon disulfide. Increased recoveries are obtained by the following modifications: adding a reducing agent (stannous chloride) to the sample before treatment with hot acid; svibstituting diluted sodium hydroxide for lead acetate solution to remove hydrogen sulfide and other interferences; and using boiling diluted hydrochloric acid. With these modifications, recoveries of N,N-dimethyldithiocarbamates from crops ranged from 85.3 to 103.8% (average 94.7%). Ethylenebisdithiocarbamates, with the exception of zineb (range 89.1–96.8%, average 92.0%), gave appreciably lower recoveries, indicating further study is necessary.

Rapid Field Screening Method for Flat Sour Spoilage

1985 ◽  
Vol 50 (6) ◽  
pp. 1719-1720 ◽  
Author(s):  
J. M. DAMARÉ ◽  
G. W. KRUMM ◽  
R. W. JOHNSTON
Keyword(s):  
Screening Method ◽  
Field Screening

Determination of Dithiocarbamate and Its Breakdown Product Ethylenethiourea in Fruits and Vegetables

1995 ◽  
Vol 78 (5) ◽  
pp. 1238-1243 ◽  
Author(s):  
Nazir Ahmad ◽  
Lin Guo ◽  
Peter Mandarakas ◽  
Sevieone Appleby
Keyword(s):  
Carbon Disulfide ◽  
Fruits And Vegetables ◽  
Residue Analysis ◽  
Headspace Analysis ◽  
Internal Standard ◽  
Detector Response ◽  
Breakdown Product ◽  
Uv Detector ◽  
Column Temperature ◽  
Sample Extract

Abstract Improved methods for determination in fruits and vegetables of ethylene bisdithiocarbamate (EBDC) residues as carbon disulfide by gas–liquid chromatographic headspace analysis and of othylenethio-urea (ETU) residues by liquid chromatography (LC) are described. Improvements to the EBDC procedure include increased sensitivity by use of 140 mL crimp seal samples bottles fitted with silicone seals, which are leak-proof and reduce headspace volume; use of a Porapak column, which allows use of higher column temperature for better residue separation; and inclusion of thiopheno as an internal standard for bettor quality control. The relationship between the logarithm of the response of carbon disulfide divided by the thiophene response versus concentration of carbon disulfide is expressed by the regression equation Y = 1.011 X + 0.008, with a correlation coefficient r2 = 0.993. Mean recoveries from 8 commodities spiked with mancozcb at 1 and 3 mg/kg, equivalent to 0.473 and 1.419 mg/kg carbon disulfide, are 94.2 ±10 and 98.3 ± 13%, respectively. The Improved LC procedure for ETU residue analysis requires minimal cleanup of sample extract, no derivatization prior to injection, and no specialized LC detectors for quantitation. The UV detector response at 240 nm Is linearly related to ETU concentration [Y = (3.18X – 0.778) × 1000. r2 = 0.997]. Moan ETU recovery from 5 commodities spiked at 0.2 to 5 mg/kg is 93.9 ± 6%. ETU residues of 0.02 to 0.25 μg/g were detected in macerated samples of fruits and vegetables spiked with man-cozeb at 5 μg/g and incubated at room temperature for 3 days. The improved procedures were used to analyze EBDC and ETU residues in fruits and vegetables sampled at a wholesale Sydney produce market. Approximately 30% of samples tested contained EBDC residues, whereas ETU residues in the same samples were below the detection limit of the analytical method (<0.02 mg/kg).

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