Modified gas chromatographic/mass spectrometric method for determination of daminozide in high protein food products

A modified version of the Conditt and Baumgardner gas chromatographic/mass spectroscopic (GC/MS) method for determination of daminozide in peanut butter and raw peanuts is described. Daminozide in the food product is hydrolyzed to unsymmetrical dimethylhydrazine (UDMH) by sodium hydroxide digestion. The generated UDMH is distilled from the food matrix and captured by reaction with salicylaldehyde in a condensation trap. Resulting high pH distillates generated by peanuts and peanut products are adjusted back to a pH of 5-6 through addition of glacial acetic acid. After thermal incubation and extraction into methylene chloride, salicylaldehyde dimethylhydrazone is separated from interferences by capillary GC and quantitated by MS using the selective ion monitoring (SIM) mode. Quantitation of daminozide is based on the ratio of the salicylaldehyde dimethylhydrazone molecular ion (m/z 164) to the molecular ion (m/z 153) of the internal standard, 4-nitroanisole. Confirmation of daminozide identity is determined by relative intensity of the m/z 164 ion to the m/z 120 (C7H4ON) ion. Improved m/z 164 ion intensity and reduction of neighboring interferences due to acetic acid treatment permitted a daminozide detection limit of 0.005 ppm in a 50 g sample and an associated 0.02 ppm limit of quantitation. This modification is specific for high protein samples that generate high pH distillates such as peanuts and peanut products and is not specifically intended for analysis of low protein samples.     

Improved gas chromatographic method for determination of daminozide by alkaline hydrolysis and 2-nitrobenzaldehyde derivatization and survey results of daminozide in agricultural products

An improved method was developed for the quantitative determination of daminozide. This new method combines the alkaline hydrolysis and distillation steps of the PAM II method for daminozide with the derivatization, cleanup, and gas chromatographic determination steps of the Wright method for unsymmetrical dimethyl hydrazine (UDMH). The minimum detectable level is 0.05 ppm. Recoveries range from 85 to 110% when daminozide is added at 0.1 to 1.0 ppm, and are generally 40% at the 0.05 ppm level. A variety of domestic and imported products were analyzed by this improved method and daminozide was detected in 33 of the 98 samples analyzed. Levels detected ranged from a trace amount to 0.80 ppm. The identity of UDMH hydrazone was confirmed by mass spectrometry in many samples, thus confirming the presence of daminozide. Two samples containing daminozide were analyzed independently by a second laboratory and the findings were closely duplicated.     

Gas chromatographic/mass spectrometric determination of daminozide in high protein food products

A gas chromatographic/mass spectrometric (GC/MS) method for determining daminozide in high protein products has been developed. Daminozide is hydrolyzed in the presence of a strong base to form unsymmetrical dimethylhydrazine (UDMH) which is then distilled from the food matrix. A stable derivative is formed by reacting UDMH with salicyladehyde to form salicyaldehyde dimethylhydrazone. This derivative is separated and quantitated by GC/MS using selected ion monitoring (SIM) of key ions in the fragmentation pattern: m/z 164 (molecular ion of hydrazone) and m/z 120 (C7H6ON). An internal standard, 4-nitroanisole, is monitored at m/z 153 (molecular ion) and m/z 123 (C6H5O2N). The limit of detection is 0.01 ppm daminozide in a 50 g sample; however, because of variation at low levels, the limit of quantitation is 0.1 ppm. Recoveries are 90% or greater from peanuts and peanut butter spiked at the 0.1-2 ppm level. Reproducibility of the method depends on the food matrix and is 26% RSD in the worst case. Data are compared for the GC/MS method and the official EPA colorimetric procedure. Results showed a high bias in the colorimetric method, especially when roasted peanut products were analyzed.     

Gas chromatographic determination of captan, folpet, and captafol residues in tomatoes, cucumbers, and apples using a wide-bore capillary column: interlaboratory study.

An interlaboratory study of the determination of captan, folpet, and captafol in tomatoes, cucumbers, and apples was conducted by 4 laboratories using wide-bore capillary column gas chromatography with electron capture detection. The 3 fungicides were determined using the Luke et al. multiresidue method modified to include additional solvent elution in the optional Florisil column cleanup step used with this method. The crops were fortified with each fungicide at 3 levels per crop. Mean recoveries ranged from 86.2% for a 25.1 ppm level of captan in apples to 115.4% for a 0.288 ppm level of captafol in apples. Interlaboratory coefficients of variation ranged from 3.4% (24.7 ppm folpet) to 9.7% (0.243 ppm captafol) for tomatoes; from 2.8% (2.0 ppm captafol) to 8.2% (24.8 ppm captan) for cucumbers; and from 1.5% (0.234 ppm folpet) to 22.1% (0.266 ppm captafol) for apples.     

Identification of O,O-dialkyl-S-methylphosphorodithioate residues in fish

O,O-Dialkyl-S-methylphosphorodithioates were found in Mississippi River buffalo fish caught near several chemical plants and oil refineries in Hartford and Wood River, IL. These chemicals, which have not been previously recognized as environmental or food contaminants, were identified and quantitated by a procedure similar to the AOAC multiresidue method for organochlorine and organophosphorus pesticides, using gas chromatography (GC) with flame photometric detection (FPD). The key to their identification was a GC/FPD retention time pattern that was virtually the same as that for the diazomethane reaction products of a commercial zinc dialkyl dithiophosphate motor oil additive. GC/mass spectrometry (MS) showed that the compound producing the largest GC/FPD peak contained butoxy groups. The identification of this compound as O,O-di(2-methylpropyl)-S-methyl-phosphorodithioate (Compound C) was confirmed by GC/MS analysis by comparison with the authentic material. The buffalo fish contained 0.15 ppm Compound C and 0.5 ppm total O,O-dialkyl-S-methylphosphorodithioates. Subsequent analyses of fish from other areas showed that these contaminants were not limited to the Hartford-Wood River area. Lower residue levels of Compound C, ranging from 0.01 to 0.05 ppm, were found in fish from the Mississippi River at Sauget, IL, and from the Delaware River and Newark Bay in NJ.     

Postharvest treatments for the reduction of mancozeb in fresh apples.

The objective of this study was to determine the effectiveness of chlorine, chlorine dioxide, ozone, and hydrogen peroxyacetic acid (HPA) treatments on the degradation of mancozeb and ethylenethiourea (ETU) in apples. This study was based on model experiments at neutral pH and temperature. Fresh apples were treated with two different levels of mancozeb (1 and 10 microg/mL). Several of the treatments were effective in reducing or removing mancozeb and ETU residues on spiked apples. Mancozeb residues decreased 56-99% with chlorine and 36-87% with chlorine dioxide treatments. ETU was completely degraded by 500 ppm of calcium hypochlorite and 10 ppm of chlorine dioxide at a 1 ppm spike level. However, at a 10 ppm spike level, the effectiveness of ETU degradation was lower than observed at 1 ppm level. Mancozeb residues decreased 56-97% with ozone treatment. At 1 and 3 ppm of ozone, no ETU residue was detected at 1 ppm of spiked mancozeb after both 3 and 30 min. HPA was also effective in degrading the mancozeb residues, with 44-99% reduction depending on treatment time and HPA concentrations. ETU was completely degraded at 500 ppm of HPA after 30 min of reaction time. These treatments indicated good potential for the removal of pesticide residues on fruit and in processed products.     

Gas chromatographic determination of N-nitrosodialkanolamines in herbicide Di- or trialkanolamine formulations

A modified method is presented to determine trace quantities of N-nitrosodiethanolamine (NDElA) and N-nitrosodiisopropanolamine (NDiPlA) in the triisopropanolamine (TiPlA) formulation of a mixture of picloram and 2,4-D. Aqueous sample is extracted with dichloromethane to remove organic interferences, and then the aqueous layer is passed sequentially through chloride anion exchange column, hydrogen cation exchange column, and Clin-Elut extraction tube. The final eluate, 10% acetone in ethyl acetate, is concentrated. The isolated nitrosamines are converted to the corresponding trimethylsilyl (TMS) derivatives and determined by gas chromatography (GC) on a DB1 column coupled with a thermal energy analyzer (GC-TEA). Eight samples of commercial TiPlA formulations are analyzed. Maximum detected levels of NDElA and NDiPlA were 0.6 and 0.9 ppm, respectively, expressed relative to total weight of active ingredients. Analysis of 13 samples of herbicide DElA formulation using a previously established method and a DB225 column gave NDElA results of 0.7-6.0 ppm. NDiPlA was not detected in those samples. Results are confirmed by GC-mass spectrometry (GC/MS) with oxygen negative chemical ionization (ONCI) detection. Detection limits for both nitrosamines are 0.05 or 0.07 ng (0.1 or 0.17 ppm) for GC-TEA detection, depending on the analytical columns used, and 20 pg (0.04 ppm) for GC/MS detection. Recoveries of NDElA are 87-109% for DElA formulation spiked at 2.6 and 3.9 ppm and 90-115% for TiPlA formulation spiked at 0.2-0.3 ppm. Similarly, recoveries of NDiPlA are 95.7-100% for the DElA formulation spiked at 0.24 and 0.48 ppm, and 82-118% for the TiPlA formulation spiked at 0.2-0.3 ppm.     

Confirmatory method for sulfamethazine residues in cattle and swine tissues, using gas chromatography--chemical ionization mass spectrometry

A gas chromatographic (GC) method has been reported for the determination of sulfamethazine residues in cattle and swine tissues. The extracts from this procedure were found to be directly amenable to examination by gas chromatography-mass spectrometry (GC-MS), allowing positive confirmation of an apparent residue of sulfamethazine. Chemical ionization mass spectrometry (CIMS) was chosen as the MS technique because it generated an ion indicative of intact sulfamethazine and fragment ions indicative of the amine functionality and sulfanil moiety. Positive ion (PI) chemical ionization mass spectrometry was adequate by itself for a confirmatory technique. Negative ion (NI) chemical ionization mass spectrometry alone could not be used for the confirmatory analysis of sulfamethazine, but it did offer a means to check the quantitative data from the positive ion analyses and provided complementary confirmatory data. Satisfactory recoveries were obtained for sulfamethazine in swine and cattle tissues at the tolerance level of 0.1 ppm. Apparent sulfamethazine residues in control tissues were less than 0.01 ppm.     

Nitrogen fertilization and daminozide effects on growth,yield, and quality of concord grapes

Abstract

Yield and productivity of Concord grapes trained to the Geneva Double Curtain system were examined over a period of three seasons (1986–1988). Factorial rates of N fertilization and the growth regulator, daminozide, were applied. Results showed that daminozide at 750 ppm combined with any N fertilization level in the study increased yield without sacrificing fruit quality or vine growth. Soil N fertilization at the rates applied did not significantly affect growth, yield or quality even though higher N rates increased leaf petiole N contents. During the three year study, no interaction was found between nitrogen and daminozide on yield.

Received for publication 6/15/91. Salaries and research support provided in part by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University. Journal Article No. 116–90.     

Gas chromatographic method for determination of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol (TCP) in dates.

A method is described for the determination of the insecticide chlorpyrifos and its metabolite TCP in green, unprocessed, and processed dates with the seeds incorporated. After extraction, chloropyrifos is cleaned up using Florisil and analyzed using a gas chromatography (GC) equipped with a nitrogen/phosphorus detector. TCP is derivatized using bis-(trimethylsilyl)-acetamide (BSA) to form the TCP-derivative and analyzed by a gas chromatograph equipped with a Hall electrolytic conductivity detector. Recoveries of chlorpyrifos from all fortified dates (0.05 and 0.1 ppm) ranged from 86 to 110% with an average of 94.5%. Recoveries of TCP from all fortified dates (0.1 and 0.2 ppm) ranged from 79 to 99% with an average of 86%. Limits of detection for chlorpyrifos and TCP in green, unprocessed, and processed dates were 0.02 and 0.05 ppm, respectively.     

Determination of daminozide residues in apple pulp using HPLC-DAD-UV

This paper reports an HPLC-UV method to determine daminozide residues in apple pulps adopting the recently introduced EU limit of 0.01 mg/kg for baby food preparation (Commission Directive 1999/39/CE). The method is based on alkaline hydrolysis of daminozide to N',N'-dimethylhydrazine (UDMH), which is recovered by distillation and subsequently derivatizated with salicyl aldehyde to salicyl aldehyde-N,N-dimethylhydrazone under strongly basic conditions. The resulting solution was cleaned up with Extrelut 20 NT and dichloromethane as eluent, then analyzed by HPLC with a C18 column and a mobile phase programmed from 50:50 AcCN/H(2)O to 100% AcCN. The salicyl aldehyde-N,N-dimethylhydrazone was selectively detected through two diagnostic UV absorption maxima at 295 and 325 nm, which have strong molar absorbivities. Recoveries of daminozide at 0.01 mg/kg were above 80%. The limits of detection (LODs) of salicyl aldehyde-N,N-dimethylhydrazone expressed as daminozide concentration were 100 pg/microL at 295 nm and 150 pg/microL at 325 nm, and the limits of quantitation (LOQs) of daminozide were 0.0013 mg/kg at 295 nm and 0.0022 mg/kg at 325 nm.     

Development of a gas chromatographic method for fungicide cymoxanil analysis in dried hops

An analytical method for detecting cymoxanil [2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino)acetamide] residues in dried hops was developed utilizing liquid-liquid partitioning, automated gel permeation chromatography (GPC), solid phase extraction (SPE) cleanup, and gas chromatography (GC). Method validation recoveries from dried hops were 96 +/- 12, 108 +/- 11, and 136 +/- 8% over three levels of fortification (0.05, 0.5, and 1.0 ppm, respectively). The hop samples from three field sites, which were treated with cymoxanil, had residue levels ranging from 0.146 to 0.646 ppm. The detection limit and the quantitation limit of the method developed in the present study were 0.022 and 0.050 ppm, respectively.     

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.     

Determination of quinomethionate (6-methylquinoline-2,3-diyldithiocarbonate) residues in crops by in situ fluorometry.

A simple method is described for the quantitative determination of quinomethionate (6-methylquinoline- 2,3 - diyldithiocarbonate) in crops. The pesticide residue is extracted with acetonitrile and partitioned in petroleum ether. After separation from the co-extractives by thin layer chromatography (TLC), the fluorescence is measured directly on a silica gel TLC plate. An average of 89% recovery is obtained at the 0.05 ppm level in apples, peaches, pears, and tomatoes.     

Novel 1,3-dioxanes from apple juice and cider

Extracts obtained by XAD solid-phase extraction of apple juice and cider were separated by liquid chromatography on silica gel. Several new 1,3-dioxanes including the known 2-methyl-4-pentyl-1,3-dioxane and 2-methyl-4-[2'(Z)-pentenyl]-1,3-dioxane, were identified in the nonpolar fractions by GC/MS analysis and confirmed by chemical synthesis. The enantioselective synthesis of the stereoisomers of the 1,3-dioxanes was performed using (R)- and (R,S)-octane-1,3-diol and (R)- and (R,S)-5(Z)-octene-1,3-diol as starting material. Comparison with the isolated products indicated that the natural products consisted of a mixture of (2S,4R) and (2R,4R) stereoisomers in the ratio of approximately 10:1, except for 1,3-dioxanes generated from acetone and 2-butanone. It is assumed that the 1, 3-dioxanes are chemically formed in the apples and cider from the natural apple ingredients (R)-octane-1,3-diol, (R)-5(Z)-octene-1, 3-diol, (3R,7R)- and (3R,7S)-octane-1,3,7-triol, and the appropriate aldehydes and ketones, which are produced either by the apples or by yeast during fermentation of the apple juice.     

Determination of chlorinated methylthiobenzenes and their sulfoxides and sulfones in fish

A procedure was developed to determine chlorinated methylthiobenzenes and their respective sulfur oxidation products in fish. Perch samples fortified at the 0.1 ppm level with 2,4,5-trichloromethylthiobenzene, pentachloromethylthiobenzene, and their sulfoxides and sulfones were extracted and cleaned up using an adaptation of the official AOAC method for multiple residues of organochlorine pesticides. The Florisil column cleanup was modified; 200 mL 6% petroleum etherethyl ether eluted the methylthiobenzenes, 200 mL 50% PE-EE eluted the sulfones, and 200 mL EE eluted the sulfoxides. Recoveries determined by electron capture (ECD) gas chromatography (GC) were 75-101% for the methylthiobenzenes and their sulfones and 63-93% for the sulfoxides. Co-extracted materials in the Florisil eluates that interfered with the ECD/GC quantitation were removed by partitioning the sulfoxides and sulfones into sulfuric acid and by thin layer chromatography on silica gel, using methylene chloride-hexane (50 + 50) as the developing solvent. Seven fish samples containing residues of chlorinated benzenes or polychlorinated biphenyls (PCBs) were examined for chlorinated methylthiobenzenes, methylthio-PCBs, and their oxidation products by matching GC retention times obtained with the EC detector and a flame photometric detector operated in the sulfur mode. These analytes were not found in the fish samples above a detection level equivalent to 0.02 ppm 2,4,5-trichloromethylthiobenzene.     

Monitoring residues of carbendazim (applied as benomyl) and thiabendazole in Wellspur apples

Residues of benomyl (determined as carbendazim, widely accepted as MBC) and of thiabendazole in Wellspur apples were monitored after the apples were treated postharvest by immersion in a bath with each of the fungicides separately and stored under refrigeration. Whole fruit and pulp analyses were conducted over the period beginning 1 day after treatment and lasting up to 200 days afterwards. Under the conditions described, both benomyl (expressed as parts per million of carbendazim) and thiabendazole were found in the fruits in the following average amounts: 0.44 +/- 0.03 and 0.11 +/- 0.03 ppm benomyl (as carbendazim) in whole fruit and in pulp, respectively; 0.98 +/- 0.10 and 0.39 +/- 0.10 ppm thiabendazole in whole fruit and in pulp, respectively.     

U.S. market basket study to determine residues of the insecticide chlorpyrifos.

A market basket study was conducted to measure residues of the insecticide chlorpyrifos in samples of apples, applesauce, apple juice, fresh orange juice, tomatoes, peanut butter, whole milk, ground beef, and pork sausage collected during a 12-month period from 200 grocery stores across the United States. Approximately 90% of the samples contained no detectable levels of chlorpyrifos, and all residues detected were below tolerances, the legal limits for the United States. No values greater than the limit of quantitation (LOQ) were found in applesauce (LOQ = 0.008 ppm), apple juice (LOQ = 0.003 ppm), whole milk (LOQ = 0.006 ppm), ground beef (LOQ = 0.005 ppm), or pork sausage (LOQ = 0.007 ppm) samples. Only one fresh orange juice sample contained residues greater than the LOQ at 0.015 ppm. Only about 20% of the apples (maximum = 0.052 ppm), 20% of the tomato samples (maximum = 0.058 ppm), and 50% of the peanut butter samples (maximum = 0.021 ppm) contained quantifiable residues.     

Determination of N-nitrosodiethanolamine in dinoseb formulations by mass spectrometry and thermal energy analyzer detection

A new method is described to determine trace quantities of N-nitrosodiethanolamine (NDElA) in aqueous diethanolamine (DElA) formulations and in oil solutions of dinoseb. A formate anion-exchange column is used in series with a cation-exchange column if there is DElA in the formulation. The eluate is then passed through a Clin Elut column. Depending on the concentration of NDElA in the sample, a packed silica-gel column is used to purify the extract further. This extract is analyzed on a liquid chromatograph coupled with a thermal energy analyzer (LC/TEA), using a mixture of methanol-hexane-methylene chloride containing 0.1% acetic acid (8 + 56 + 35) as the mobile phase. This solvent system gives good separation of NDElA from trace quantities of dinoseb remaining in the extract. The NDElA is also converted to the trimethylsilyl derivative and analyzed by gas chromatograph coupled with a mass spectrometer (GC/MS). Analyses of 11 commercial samples of dinoseb diethanolamine salt showed NDElA levels of 116-2409 ppm expressed relative to the weight of dinoseb. In contrast, analyses of 2 samples of organic solutions of technical dinoseb showed NDElA levels to be nondetectable and 0.3 ppm, respectively. Limit of detection by LC/TEA is 6.5 ng (0.5 ppm), and by GC/MS it is 0.02 ng (0.15 ppm). Recoveries from samples spiked at 0.514-1664 ppm range from 92.2 to 105.2%.     

Levels of 3,3',4,4'-tetrachloroazobenzene in diuron and linuron herbicide formulations

Levels of 3,3',4,4'-tetrachloroazobenzene (TCAB) were determined by capillary gas chromatography (GC) with electron-capture detection (ECD) in 25 samples of diuron and linuron formulations obtained from the Canadian market. Acidic aqueous methanol was used to retain urea herbicide and the neutral TCAB was allowed to partition into hexane. Silica gel was used for cleanup of the hexane extract, followed by GC/ECD determination. Recovery data obtained at 4 different spiking levels (i.e., 0.3, 0.1, 1.0, and 5.0 ppm) in linuron averaged 93, 86, 85, and 97%, respectively. For diuron, spiking was done at 0.5, 1.0, and 5.0 ppm levels and the corresponding average percent recoveries were 95, 101, and 104. The TCAB contamination level observed in diuron on a 100% active ingredient basis ranged from 0.15 to 3.38 ppm, whereas in linuron, it varied from 0.91 to 10.28 ppm.