Survey of vomitoxin contamination of 1980 Ontario white winter wheat crop: results of survey and feeding trials.

During the harvesting of the 1980 Ontario white winter wheat crop, producers noticed pink discoloration on kernels; this was attributed to Fusarium mold. Grain elevator and boatload samples were analyzed for mycotoxin contamination. Vomitoxin levels up to 8 ppm were detected in samples from southwestern Ontario. Other suspected mycotoxins were either nondetectable or present in trace amounts. Fusarium-contaminated wheat and clean wheat were added to swine and poultry diets for feeding trials. Feed refusal and decreased weight gains were observed in pigs fed diets containing 0.3 and 0.7 ppm vomitoxin, but there was no vomiting or other ill effects. Adult roosters and laying hens fed diets containing vomitoxin levels similar to those of the pig diets did not show any overt toxicological effects. Chemical analysis of suspected field cases of vomitoxin-contaminated feed did not reveal high vomitoxin levels.

High pressure chromatography determination of aldicarb, aldicarb sulfoxide, and aldicarb sulfone in potatoes.

An ion-suppression reverse phase high pressure liquid chromatographic method is described for the determination of aldicarb, aldicarb sulfoxide, and aldicarb sulfone in potatoes. Samples are extracted with methylene chloride and Na2SO4, evaporated to dryness, and cleaned up using Sep-Pak silica and Sep-Pak-C18 cartridges. The extract can be successfully analyzed by high pressure liquid chromatography on either a mu LiChrosorb RP-18 or mu Bondapak C18 column and quantitated using a variable wavelength ultraviolet detector set at either 220 or 247 nm. The mobile phase is acetonitrile-buffer (4 + 96) and (30 + 70), buffered to pH 7.6 and flowing at 2 mL/min. Recoveries ranged from 80 to 100%. The minimum detectable amount was 37.5 ng, which easily permitted the quantitation of 0.1 ppm aldicarb sulfone in 75 g sample. The recovery of aldicarb was low because of its rapid enzymatic oxidation to aldicarb sulfoxide and sulfone.

High pressure liquid chromatographic determination of naphthaleneacetamide residues in apples.

A simple, rapid, and accurate method has been developed for the determination of naphthalene-acetamide (NAAmide) residues in apples. After extraction with chloroform, separation is performed on an RP-8 high pressure liquid chromatographic column using acetonitrile-water (30 + 70) buffered to pH 3.5 at a flow rate of 1.7 mL/min. Either a variable wavelength ultraviolet detector set at 220 nm or a fluorometric detector can be used for quantitation. Average recoveries at the 0.01 and 0.1 ppm spiking levels were 83 and 89%, respectively. Incorporation into a previously described method for naphthaleneacetic acid (NAA) residues in apples has resulted in a procedure for the samultaneous determination of NAA and NAAmide.

Confirmation of organothiophosphorus insecticide residues in fruit and vegetables by oxidative derivatization.

Oxidative derivatization of 10 organothiophosphorus insecticides at nanogram levels, with neutralized sodium hypochlorite (NaOCl) produced their respective P=O oxygen analogs, as shown by GC/MS and FT-IR analysis. In addition, phorate resulted in phorate oxon sulfoxide while methidathion gave a mixture of oxidation products. Four macro-scale oxidation products of methidathion were isolated by thin layer chromatography and 3 were identified, namely, methidaoxon, bis(2-methoxy-delta2-1,3,4-thiadiazolin-5-on-4-yl) sulfide, and the corresponding disulfide, by comparison of their infrared and mass spectra with those of authentic samples. The relative response to sulfide and disulfide products of the flame photometric detector in both the P- and S-modes is discussed. This derivatization is applied to the confirmation of chlorpyrifos, ethion, phorate, DMPA (Zytron), leptophos, and methidathion in celery, potatoes, lettuce, tomatoes, and apples at 0.25-0.5 ppm fortification levels.

Comparative study of the linearity and sensitivity of electron capture and flame photometric detectors using a pesticide standard.

A study was undertaken to compare and evaluate the different types of 63Ni and 3H electron capture (ECD) and flame photometric detectors (FPD) as part of the Canadian Check Sample Program on Pesticide Residue Analysis. Twenty-seven laboratories were supplied with chlorpyrifos standard solutions for the determination of linear range and minimum detectable amounts (MDA). Each laboratory selected its own operating conditions except for the FPD study. Results for the FPD were compared with standardized flame conditions designed to optimize the exponential factor i, the S-mode. The MDA of the ECDs (pulsed and direct-current) ranged from 0.09 to 0.17 pg/sec for 63Ni and 3H sources respectively. The corresponding MDA for the linearized ECDs (pulse modulated or constant current) was 0.04 pg/sec and a linear range of 10(4) or greater with nitrogen as the carried gas. Use of argon/methane and a pulse width of 0.1 usec extended this range to 10(5) but the sensitivity was not as great as with nitrogen carrier gas. The practical limit of detector sensitivity was found to be instrument dependent depending primarily on the noise level. In the FPD study, operating in the P-mode gave an average MDA of 5.97 pg/sec and a linear range of 2 x 10(3). Similarly, the S-mode parameters were 81.1 pg/sec and 8 x 10(2) respectively with an average exponential factor of n 1.8. Attempts to apply optimized detector gas-flow conditions improved sensitivity and linearity in the S-mode only.

High pressure liquid chromatographic determination of naphthaleneacetic acid residues in apples.

An ion-suppression reverse phase high pressure liquid chromatographic method is described for determining naphthaleneacetic acid (NAA) residues in apples. Samples are extracted with acidic chloroform, filtered through pre-acidified Hy-Flo Supercel, and cleaned up by acid-base partitioning. The extract can be successfully chromatographed on either a muLiChrosorb NH2 or muBondapak C18 column and quantitated by using a variable wavelength ultraviolet detector set at 220 nm. The mobile phase is acetonitrile-water (20 + 80) buffered to pH 3.5 (MULiChrosorb column) or pH 5.2 (MUBondapak column) and flowing at 1.0--2.0 ml/min. Recoveries ranged from 86 to 98%. The minimum detectable amount was 0.5 ng, which easily permitted the quantitation of 0.01 ppm NAA in 50 g sample. A fluorometric detector was 4 times as sensitive, using an excitation wavelength of 220 mm and monitoring the emission at 340 nm. For this detector, the minimum detectable amount was 0.12 ng NAA.

Gas-liquid chromatographic analysis of ethephon and fenoprop residues in apples and their decline before and after harvest.

Ethephon (2-chloroethylphosphonic acid) and fenoprop (2-(2,4,5-trichlorophenoxy) propionic acid) may be determined in the same apple sample. After extraction with methanol, 2 separate methylation procedures were required to quantitatively convert each compound. Ethephon was esterified with diazomethane and analyzed by a flame photometric detector in the P-mode. Fenoprop was esterified with boron trifluoride/methanol and analyzed by electron capture gas chromatography. Average recoveries were about 95% at 0.05 ppm for both compounds. The limit of detection was 0.05 ppm for ethephon and 0.01 ppm for fenoprop in a 1 g sample. The persistence of both compounds before and after harvest was studied. Ethephon and fenoprop were applied simultaneously to apple trees at the recommended concentrations of 300 and 20 ppm, respectively. Ethephon residues averaged 1.6, 0.75, and 0.4 ppm at 2 hr, 10 days, and after washing at 13 days, respectively. The corresponding fenoprop residues were 0.70, 0.025, and 0.024 ppm.

Gas-liquid chromatographic determination of technical chlordane residues in food crops: interpretation of analytical data.

An interlaboratory investigation of technical chlordane residues in food crops was carried out to determine the most practical and consistent method of reporting results. Using a technical chlordane reference standard, 8 gas chromatographic stationary phases were studied for their resolution capabilities. The best separations were obtained with SE-30 and its OV-1 equivalent. Using these columns and electron capture detection, potatoes and carrots from supervised field experiments were analyzed in duplicate and quantitated by using 4 methods of calculation. The data were statistically treated to determine the precision and bias for each method. Also, 1 sample was analyzed in duplicate on 2 different occasions by 6 laboratories to substantiate the initial conclusions. Based on the criterion of high precision it is suggested that a comparison of total area under the chromatogram of the sample with total area of standard technical chlordane be the method of quantitation. Only peaks which are common to both standard and sample have any significance in this type of calculation.