Simultaneous determination of dichlorvos, trichlorfon and naled in fruits and vegetables by liquid chromatography with tandem mass spectrometry

A method for simultaneous determination of Dichlorvos (DDVP), Trichlorfon (DEP) and Naled (BRP) in fruits and vegetables by liquid chromatography with tandem mass spectrometry (LC/MS/MS) was developed. Pesticides were extracted with ethyl acetate together with phosphoric acid and anhydrous sodium sulfate, followed by an ENVI-Carb cartridge cleanup. Phosphoric acid prevented BRP from being converted to DDVP during extraction of pesticides from the sample. When the sample was dissolved in acetonitrile in a silanized glass vial, BRP and DEP remained intact. Mass spectral acquisition was performed with a TurbolonSpray (ESI) interface in the positive mode by applying multiple reaction monitoring. In LC separation, an ODS column was used with acetic acid-ammonium acetate-methanol as a mobile phase. Recoveries from 8 fruits and vegetables at the fortification level of 0.1 microg/g were 75.0-91.8% for BRP, 70.2-88.9% for DDVP, and 77.3-92.1% for DEP. The detection limits of BRP, DDVP and DEP were 1, 2 and 2 ng/g, respectively.     

Analysis of glyphosate and its metabolite, aminomethylphosphonic acid, in agricultural products by HPLC]

An analytical method for residues of the herbicide glyphosate [GLY: N-(phosphonomethyl)-glycine] and its metabolite (AMPA: aminomethylphosphonic acid) in agricultural products is described. GLY and AMPA were extracted with water (soybeans extract was moreover treated with acetone), and purified by application to a dual mini-cartridge column (octadecyl-bonded silica gel and cation-exchange silica gel) system. GLY was derivatized with 9-fluorenylmethylchloroformate, and determined by HPLC with fluorescence detection. AMPA determination was performed by HPLC employing postcolumn fluorogenic labeling with o-phthalaldehyde-mercaptoethanol. The detection limits for GLY and AMPA were 0.04 microgram/g (soybean: 0.08 microgram/g), and both recoveries from samples to which the compounds were added at the 0.2 microgram/g level (soybean: 1.0 microgram/g) were more than 65%.     

Simultaneous determination of N-methylcarbamate and urea pesticides in agricultural products by LC/MS

A simultaneous determination method of 7 N-methylcarbamate and 7 urea pesticides in agricultural products by liquid chromatography/mass spectrometry (LC/MS) has been developed. Under reversed-phase liquid chromatographic conditions, 14 pesticides were analyzed using electrospray ionization (ESI) with simultaneous acquisition of positive ions and negative ions. Fourteen pesticides were extracted with acetone, 10% NaCl solution was added, and the pesticides were re-extracted with dichloromethane. The extract was concentrated under reduced pressure, and dissolved in methanol. The detection limits of 14 pesticides ranged from 0.0012 to 0.0056 microgram/g. The recoveries of pesticides were from 36.5 to 112.5% [RSD (n = 3) ranged from 0.5 to 48.1%] for 4 agricultural products.     

Determination of ethychlozate and its degradation product in fruits by HPLC and LC/MS

A method was developed for the analysis of ethychlozate (CIE) and its decomposition compound, 5-chloro-3(1H)-indazolylacetic acid (CIA) in fruits by HPLC and LC/MS. The sample was homogenized with 1 mol/L HC1, and CIE and CIA were extracted with 5 mol/L HCl and acetone. They were extracted from the acetone extract with diethylether-n-hexane (2:1). CIE was hydrolyzed to CIA with methanol-4 mol/L KOH (1:1). The solution was made acidic, and CIA was extracted with diethylether-n-hexane (2:1). The extract was cleaned up on a silica gel column. CIA was determined by HPLC-UV and LC/MS (Scan or SIR). Four fruits were spiked with CIE or CIA at 0.5 microgram/g and analyzed by the proposed method with HPLC. The average recoveries were 77.2-83.2% for CIE and 71.2-89.2% for CIA. The concentrations determined by LC/MS were 10-25% higher than the values by HPLC. The limit of detection (LOD) of CIA standard solution by HPLC corresponds to 0.015 microgram/g of CIE in the sample. In the same way, the LOD of CIA by LC/MS (SIR) corresponds to 0.009 microgram/g of CIE in the sample.     

Simple analysis of maleic hydrazide in agricultural products by HPLC

A simplified HPLC determination method for maleic hydrazide in agricultural products was developed, and commercial agricultural crops were investigated. The homogenate of agricultural products was extracted with water. The crude extract was purified on an ACCUCAT Bond Elut extraction cartridge using water. Maleic hydrazide was analyzed by HPLC with UV detection (303 nm). The HPLC separation was performed on a ZORBAX SB-Aq column with acetonitrile-water-phosphoric acid(5:95:0.01) as the mobile phase. Recoveries of maleic hydrazide from 15 agricultural products fortified at 1.0 and 10 micrograms/g were in the ranges of 92.6-104.9% and 94.2-101.3%, respectively. The limit of detection was 0.5 microgram/g in samples. The proposed method was applied to the determination of 242 commercial vegetables and fruits. Maleic hydrazide was detected in 2 samples of imported onion at the levels of 4.9 and 7.2 micrograms/g.     

Study on the determination of pesticide residues in crops by ion-trap GC/MS/MS

Ion-trap GC/MS/MS was evaluated for the multi-residue determination of pesticides in agricultural products. Matrices were extracted from samples (spinach, carrot, onion and brown rice) with acetone and submitted to gel permeation chromatography, followed by a clean-up step through a graphite carbon cartridge. Thirty-five pesticides were added to either matrix, and analyzed by GC/MS/MS. Detection limits of pesticides by GC/MS/MS was almost the same as those by GC/MS (SIM). Coefficients of variation of peak area in 5 measurements of each pesticide at 0.1 microgram/mL or 0.05 microgram/mL with or without matrices were mostly acceptable, though those of 20 pesticides out of 35 were higher than 10% at a concentration of 0.02 microgram/mL. It was indicated that matrix artifacts, which interfere with GC/MS-Scan analysis, could be eliminated in some cases by using GC/MS/MS.     

Method-performance studies of notified analytical method for chinomethionat

Method-performance studies were conducted for the notified revised analytical method of chinomethionat in agricultural products by interlaboratory study. Six laboratories analyzed unpolished rice, cabbage, squash, lettuce and orange spiked with 0.1 microgram/g of chinomethionat in replicate. Mean values of recovery from the 5 crops ranged from 90.2 to 100.5%. Repeatability relative standard deviations ranged from 4.4 to 7.7% and reproducibility relative standard deviations ranged from 10.9 to 17.1%. The detection limits were 0.003-0.012 microgram/g.     

Clean-up method of forchlorfenuron in agricultural products for HPLC analysis

A simplified method for the determination of forchlorfenuron in agricultural products by HPLC with UV detection was investigated. A chopped sample homogenate from agricultural products was extracted with acetone. The extract was filtrated and concentrated. The residues was loaded onto a Chem Elut column and extracted with ethyl acetate. The crude extract was purified on Oasis HLB and Bond Elut PSA mini-columns using a mixture of methanol and ethyl acetate. Forchlorfenuron was analyzed by HPLC with UV detection (263 nm). HPLC separation was performed on an ODS column with methanol-water as the mobile phase. Recoveries of forchlorfenuron from several agricultural products fortified at the level of 0.1 microg/g were in the range of 87.6-99.5%. The limit of detection (S/N=3) was 0.005 microg/g in the sample.     

Simultaneous determination of pesticides in agricultural products by LC/MS/MS using clean-up with ultrafiltration

A method for simultaneous determination of multiple pesticide residues in agricultural products was developed by using a pretreatment with ultrafiltration, followed by liquid chromatography-tandem mass spectrometry (LC/MS/MS). The pretreatment process (extraction of pesticides from agricultural products with methanol, dilution of the extract with water, and ultrafiltration) gave recoveries in the range of 50-150% for 63 of 83 pesticides spiked at 0.25 microg/ g into 6 agricultural products. The detection limits of pesticides by LC/MS/MS were below 0.0005-0.05 micro/g. This method is useful for screening purposes and for multiresidue analysis of pesticides in agricultural products. Pesticide residues in 50 domestic crops were investigated by this method, and residues of 14 pesticides were detected in 30 crops.     

Determination of seventeen pesticide residues in agricultural products by LC/MS

Residues of 17 pesticides in agricultural products were determined by LC/MS with an atmospheric pressure chemical ionization (APCI) interface in both positive and negative ion modes. Pesticides were extracted with acetonitrile, and the extracts were cleaned-up with a primary and secondary amine (PSA) mini-column eluted with acetone-hexane (1:1). Rice, orange and potato were spiked with the 17 pesticides at 0.1 microgram/g and analyzed by the proposed method. The average recoveries of these pesticides usually ranged from 70 to 98% and the relative standard deviations were usually around 10%. These results suggested that LC/MS with APCI could be used to determine the residue levels of the 17 pesticides in these crops.     

Analytical method of hydramethylnon in agricultural products by LC-MS/MS

A simple determination method of hydramethylnon in agricultural products by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. The sample was homogenized with phosphoric acid and extracted with acetone. An aliquot of crude extract was re-extracted with hexane and sat. NaCl solution. In the case of tea leaf, solidification processing using ammonium chloride and phosphoric acid was performed before re-extraction with hexane. Clean-up was performed using a silica-gel mini column (500 mg). The LC separation was performed on a C18 column using methanol-water (8 : 2) containing 10 mM ammonium acetate as the mobile phase and MS detection with positive ion electrospray ionization. The calibration curve was linear between 0.002-0.2 μg/mL of hydramethylnon. Recoveries (n=5) of hydromethylnon from 10 kinds of agricultural products fortified at 0.01 μg/g (0.05 μg/g for pineapple) were 82-110%, and their relative standard deviations were 2-12%.     

Phthalate esters in human milk: concentration variations over a 6-month postpartum time

The present study investigated the levels of phthalate esters in a total of 86 human milk samples collected among 21 breast-feeding mothers over a 6-month postpartum time. Di(2-ethylhexyl) phthalate (DEHP) was the predominant ester with the arithmetic mean value of 222 ng g(-1) (range: 156-398 ng g(-1), 95% confidence limit), followed by dibutyl phthalate (DBP), 0.87 (range: 0.62-1.2) ng g(-1). Diethyl phthalate (DEP), with a mean of 0.31 ng g(-1), was detected in only a small number of samples. Weak correlations between lipid content and levels of phthalate esters were observed. The levels of phthalate esters in human milk fluctuated over the 6-month period; this may indicate a need for multiple sample collection, to calculate average concentrations over the feeding period. Multiple sample collection would provide a better estimate of the exposure of breast-fed infants to phthalate in human milk. For infants relying on breast-feeding, the mean daily intake over the first 6-month period considering a 7 kg infant consuming 750 g of milk was estimated at 167 microg d(-1) for DEHP and less than 1 microg d(-1) for DBP and DEP. While the nutritional and social benefits of breast-feeding are well established, the potential transfer of phthalate esters from mothers to breast-fed infants should also be recognized.     

Residue contents of DDVP (Dichlorvos) and diazinon applied on cucumbers grown in greenhouses and their reduction by duration of a pre-harvest interval and post-harvest culinary applications

Controlled applications of DDVP (Dichlorvos) and diazinon were carried out on cucumbers grown in two different greenhouses at different times. The first group of samples was collected 4 h after the application and the second group was collected 4 days later, which was the mean cropping period applied in this region following maturation of the cucumber plant. Additionally, control samples were collected before application. The effects of washing, peeling and predetermined storage periods, at 4 °C for 3 and 6 days, on the reduction of residue levels in the plant tissues were investigated in the two groups. A gas chromatographic method, using acetone, dichloromethane and petroleum ether, as extraction solvents was used to analyse residual DDVP and Diazinon in cucumbers, with obtained recoveries greater than 81%. DDVP and Diazinon were determined by gas chromatography–electron capture detection (GC–ECD) equipped with a 5% phenylmethylpolysiloxane-coated fused-silica capillary column.Results showed that residue levels in samples, which were collected after 4 days following the pesticide application, were significantly lower than the samples collected after 4 h subsequent to the pesticide application. Culinary applications, such as washing and peeling and refrigeration storage, were also effective in reducing the residue levels.     

Determination of dimethylformamide in food additive sucrose esters of fatty acids using solid-phase extraction

A simple method using Florisil cartridges was developed for the determination of dimethylformamide (DMF) in sucrose esters of fatty acids present in sugar esters (SuE) and sucrose acetate isobutyrate (SAIB) used as food additives. SuE was dissolved in acetone and loaded on a Florisil cartridge. SAIB was dissolved in hexane, loaded on a Florisil cartridge and washed with 10% acetone in hexane. The columns were eluted with acetone and DMF in the eluates was determined by GC with an FID detector. Recoveries of DMF at the level of 0.5-100 micrograms/g were 93.3-102.6%. The determination limit was 0.5 microgram/g.     

Liquid chromatographic method for fumonisin B1 in sorghum syrup and corn-based breakfast cereals.

The fungus Fusarium verticillioides has been found on corn and sorghum, so it is possible that one or more of these toxins may be found in corn products such as breakfast cereals and syrup prepared from sorghum. Published methods when applied to syrups spiked with fumonisins gave low recoveries, less than 50%. A method was therefore developed which would be applicable to the syrup and breakfast cereals as well. Test samples were extracted with methanol-0.1 M sodium phosphate buffer (pH3) (1 + 1). The extract was diluted with water and applied to a 1 g C18 column. The column was washed with acetonitrile-water (2 + 8). Fumonisin B1 (FB1) was eluted with acetonitrile-trifluoroacetic acid (1000 + 1). The purified extract was evaporated and the toxin was derivatized with ophthaldialdehyde mercaptoethanol. The reaction mixture was resolved on a C18 liquid chromatographic column using acetonitrile-water-acetic acid (500 + 550 + 10.5) as the mobile phase at 37 degrees C, and FB1 measured with a fluorescence detector (excitation 335 nm, emission 440 nm). Recoveries of FB1 added to samples of sorghum syrup at levels ranging from 0.1 to 1.0 microgram/g were 94-132%. Recoveries of FB1 added to samples of breakfast cereal (corn flakes) at levels ranging from 0.2 to 1.6 micrograms/g were 96-100%. The method was applied to the analysis of 35 samples of sorghum syrup collected from 15 states in the US. One sample was found to contain FB1 at 0.12 microgram/g. A total of 32 samples of breakfast cereals collected by the Food and Drug Administration inspectors from grocery stores around the Kansas City area were analysed; no FB1 was found in the breakfast cereals (< 0.01 microgram/g). Results of this study indicated that FB1 possibly is not a problem in sorghum syrup and corn-based breakfast cereals in the US.     

Performance study of analytical method for ethoxyquin in fruit

A performance study of an analytical method of ethoxyquin (ET) in apples and pears was conducted. In the proposed method, the sample was homogenized with thiourea and ET was extracted with acetone instead of hexane used in the official analytical method for ET, in order to improve the extraction efficiency. Furthermore, dibutyl hydroxytoluene was added in the test solution to prevent the decomposition of ET. For evaluation of the method. ET spiked into apples and pears at the level of 0.2 microgram/g was determined in replicate in six laboratories. Mean recoveries from apple, pear and Japanese pear were 85.3, 83.0 and 83.9%, respectively. Repeatability relative standard deviation values were 3.8-4.7% and reproducibility relative standard deviation values were 7.8-11.3%. The detection limits were 0.001-0.025 microgram/g in the six laboratories; this value may reflect instrument performance. ET spiked into apples and pears at the level of 0.2 microgram/g was detected by both LC/MS and GC/MS.     

Aluminium content in foods with aluminium-containing food additives

The aluminium (Al) content of 105 samples, including bakery products made with baking powder, agricultural products and seafoods treated with alum, was investigated. The amounts of Al detected were as follows (limit of quantification: 0.01 mg/g): 0.01-0.37 mg/g in 26 of 57 bakery products, 0.22-0.57 mg/g in 3 of 6 powder mixes, 0.01-0.05 mg/g in all three agricultural products examined, 0.03-0.90 mg/g in 4 of 6 seafood samples, 0.01-0.03 mg/g in 3 of 11 samples of instant noodles, 0.04-0.14 mg/g in 3 of 4 samples of vermicelli, 0.01 mg/g in 1 of 16 soybean products, but none in soybeans. Amounts equivalent to the PTWI of a 16 kg infant were detected in two samples of bakery products, two samples of powder mixes and one sample of salted jellyfish, if each sample was taken once a week. These results suggest that certain foods, depending on the product and the intake, might exceed the PTWI of children, especially infants.     

Simultaneous determination of N-methylcarbamate pesticides and their metabolites in agricultural products

We investigated the determination of N-methylcarbamate pesticides and their metabolites in agricultural products by HPLC with post-column fluorescence detection after clean-up with an SPE cartridge. The homogenate of agricultural products was extracted with acetone. The crude extract was partitioned between 5% sodium chloride solution and dichloromethane, and the dichloromethane layer was concentrated to dryness. The residue was dissolved with a mixture of acetone and n-hexane, and purified by using Supelclean ENVI-Carb SPE, Bond Elut Extraction Cartridge PSA and SAX in series with a mixture of acetone and n-hexane. N-Methylcarbamate pesticide was analyzed by HPLC with post-column reaction and fluoresce detection. N-Methylcarbamate pesticide in citrus fruits and various kinds of agricultural products could be analyzed accurately by the presented method. Recoveries of N-methylcarbamate pesticides added to several agricultural products at the level of 0.10 ppm were mostly in the range of 60-110%. The limit of detection was 0.005 ppm.     

Aluminium levels in Canadian infant formulate and estimation of aluminium intakes from formulae by infants 0-3 months old

Aluminium was determined in 282 cans of infant formulae and evaporated milks sold in Canada using graphite furnace atomic absorption spectrometry. Milk-based formulae contained average (range) concentrations of 0.129 (0.010-0.36), 0.217 (0.17-0.56) and 0.717 (0.19-2.49) micrograms/g ('as sold') in ready-to-use, concentrated liquid and powder formulae, respectively. The corresponding concentrations in the soy-based formulae were 1.98 (0.40-6.4), 1.41 (0.59-2.29) and 9.44 (3.15-18.0) micrograms/g. Evaporated milk contained 0.093 (0.022-0.34) micrograms/g. The levels varied extensively according to formula brand; e.g. for ready-to-use formulae, the range of average concentrations by formula brand were 0.42-3.28 micrograms/g for soy-based and 0.020-0.22 micrograms/g for milk-based products. Estimated aluminium ingestion from formula or milk by infants up to 3 months old ranged from 0.5 microgram per kg body weight per day (microgram/kg/day) or 2 micrograms/day for 0-1 month olds fed cow milk exclusively to 219 micrograms/kg/day (1260 micrograms/day) for 1-3 month olds fed only soy-based formulae. Consumption of only the formulae brand having the highest mean aluminium level (3.28 micrograms/g) by 1-3 month old infants could result in an intake of 363 micrograms/kg/day (2088 micrograms/day). The estimates assume that the sole source of aluminium is the formula or milk and do not include any potential contribution from other foods or water.     

Determination of benzylaminopurine in agricultural products

A simplified method for the determination of benzylaminopurine in agricultural products by LC/MS was investigated. Benzylaminopurine in agricultural products was extracted with acetone and the extract was concentrated to below 30 mL. Buffer solution of pH 9.0 and ethyl acetate were added to the residue, and the solution was shaken. The ethyl acetate layer was evaporated to dryness, and the residue was dissolved in acetone-n-hexane (1 : 1). The solution was applied to a SAX/PSA mini-column, which was then rinsed with acetone-n-hexane (1 : 1). Benzylaminopurine was eluted with acetone-n-hexane (1 : 1) containing 1% water. The eluates were evaporated to dryness, and the residue was dissolved in 10 mmol/L ammonium acetate-methanol (1 : 1). Benzylaminopurine was analyzed by LC/MS. The MS detection was performed in the selected ion monitoring (SIM) mode, with detection of the M+H(+) ion of benzylaminopurine (m/z 226) generated by electrospray ionization (ESI). Recoveries of benzylaminopurine from 15 agricultural products were in the range of 83.1-97.2%. The limits of detection (S/N=3) of benzylaminopurine in all samples except green tea and in green tea were 0.0003 and 0.0012 microg/g, respectively.