Effect of heat processing and storage time on migration of bisphenol A (BPA) and bisphenol A-diglycidyl ether (BADGE) to aqueous food simulant from Mexican can coatings

Effects of heat processing and storage time (up to 70 days) on migration of bisphenol A (BPA) and bisphenol A-diglycidyl ether (BADGE) from can coatings into an aqueous food simulant were determined. Distilled water was canned in two types of Mexican cans: for tuna and for jalape?o peppers. Results showed that there is an effect of heat treatment on migration of both compounds. Storage time did not show any effect in BPA migration from tuna cans. There was an effect of storage time on BPA migration from jalape?o pepper cans. Results for BADGE migration were affected by its susceptibility to hydrolyze in aqueous simulants. BADGE concentration decreased, or was not detected, during storage in both types of cans. Migration levels for BPA and BADGE were within 0.6-83.4 and <0.25-4.3 microg/kg, respectively. Both were below European and Mercosur legislation limits. Other migrating compounds were detected, although no identification was performed.     

Concentration of bisphenol A in highly consumed canned foods on the U.S. market

Metal food and drink cans are commonly coated with epoxy films made from phenolic polymers produced from bisphenol A (BPA). It is well established that residual BPA monomer migrates into can contents during processing and storage. While a number of studies have reported BPA concentrations in foods from foreign markets and specialty foods on the U.S. market, very few peer-reviewed data for the BPA concentrations in canned food from the U.S. market were available. This study quantified BPA concentrations in 78 canned and two frozen food products from the U.S. market using an adaptation of a previously reported liquid chromatography-tandem mass spectrometry method. The tested products represented 16 different food types that are from the can food classifications that constitute approximately 65% of U.S. canned food sales and canned food consumption. BPA was detected in 71 of the 78 canned food samples but was not detected in either of the two frozen food samples. Detectable BPA concentrations across all foods ranged from 2.6 to 730 ng/g. Large variations in BPA concentrations were found between different products of the same food type and between different lots of the same product. Given the large concentration ranges, the only distinguishable trend was that fruits and tuna showed the lowest BPA concentrations. Experiments with fortified frozen vegetables and brine solutions, as well as higher BPA concentrations in canned food solids over liquid portions, clearly indicated that BPA partitions into the solid portion of foods.     

Determination of bisphenol a and bisphenol B residues in canned peeled tomatoes by reversed-phase liquid chromatography

Bisphenol A (BPA) and bisphenol B (BPB) concentrations were determined in peeled canned tomatoes of different brands bought in Italian supermarkets. Tomato samples analyzed were packaged in cans coated with either epoxyphenolic lacquer or low BADGE enamel. A solid phase extraction (SPE) was performed on C-18 Strata E cartridge followed by a step on Florisil cartridge. Detection and quantitation were performed by a reversed phase high-performance liquid chromatography (RP-HPLC) method with both UV and fluorescence detection (FD). On the total of 42 tested tomato samples, BPA was detected in 22 samples (52.4%), while BPB was detected in 9 samples (21.4%). BPA and BPB were simultaneously present in 8 of the analyzed samples. The levels of BPA found in this study are much lower than the European Union migration limits of 3 mg/kg food and reasonably unable to produce a daily intake exceeding the limit of 0.05 mg/kg body weight, established by European Food Safety Authority.     

Levels of bisphenol A in canned liquid infant formula products in Canada and dietary intake estimates

A sensitive, efficient, and reproducible method, based on solid phase extraction and derivatization with acetic anhydride followed by gas chromatography-mass spectrometry in selected-ion monitoring mode, was developed for the determination of bisphenol A (BPA) in liquid infant formula. The method quantification limit was 0.5 ng g(-1). Extraction recoveries were 85-94% over the concentration range of 2.5-20 ng g(-1). Good reproducibility of the method was observed at levels of 0.54 and 10.4 ng g(-1) with relative standard deviations of 5.0 and 2.8%, respectively. The method was used to analyze samples of 21 canned liquid infant formula products for BPA. BPA was detected in all samples at levels ranging from as low as 2.27 ng g(-1) to as high as 10.2 ng g(-1). The probable daily intakes of BPA due to consumption of canned liquid infant formula were estimated for infants from premature to 12-18 months of age. The maximum probable daily intake of BPA was 1.35 microg kg(-1) of body weight day(-1) for 0-1-month-old infants with the maximum formula intake, which is below the provisional tolerable daily intake for BPA established by Health Canada, 25 microg kg(-1) of body weight day(-1).     

Analysis of acrylamide,a carcinogen formed in heated foodstuffs

Reaction products (adducts) of acrylamide with N termini of hemoglobin (Hb) are regularly observed in persons without known exposure. The average Hb adduct level measured in Swedish adults is preliminarily estimated to correspond to a daily intake approaching 100 microg of acrylamide. Because this uptake rate could be associated with a considerable cancer risk, it was considered important to identify its origin. It was hypothesized that acrylamide was formed at elevated temperatures in cooking, which was indicated in earlier studies of rats fed fried animal feed. This paper reports the analysis of acrylamide formed during heating of different human foodstuffs. Acrylamide levels in foodstuffs were analyzed by an improved gas chromatographic-mass spectrometric (GC-MS) method after bromination of acrylamide and by a new method for measurement of the underivatized acrylamide by liquid chromatography-mass spectrometry (LC-MS), using the MS/MS mode. For both methods the reproducibility, given as coefficient of variation, was approximately 5%, and the recovery close to 100%. For the GC-MS method the achieved detection level of acrylamide was 5 microg/kg and for the LC-MS/MS method, 10 microg/kg. The analytic values obtained with the LC-MS/MS method were 0.99 (0.95-1.04; 95% confidence interval) of the GC-MS values. The LC-MS/MS method is simpler and preferable for most routine analyses. Taken together, the various analytic data should be considered as proof of the identity of acrylamide. Studies with laboratory-heated foods revealed a temperature dependence of acrylamide formation. Moderate levels of acrylamide (5-50 microg/kg) were measured in heated protein-rich foods and higher contents (150-4000 microg/kg) in carbohydrate-rich foods, such as potato, beetroot, and also certain heated commercial potato products and crispbread. Acrylamide could not be detected in unheated control or boiled foods (<5 microg/kg). Consumption habits indicate that the acrylamide levels in the studied heated foods could lead to a daily intake of a few tens of micrograms.     

Semicarbazide formation in azodicarbonamide-treated flour: a model study

Semicarbazide was previously found in foods that were in contact with rubber gaskets foamed at high temperatures with a blowing agent azodicarbonamide. Because azodicarbonamide is an approved flour additive in certain countries, we set out to ascertain if semicarbazide is formed during the baking process from flours containing that additive. The levels of semicarbazide in baking flour treated with azodicarbonamide and bread baked from such flours were determined by isotope dilution (13C15N2-semicarbazide) liquid chromatography electrospray tandem mass spectrometry (LC-MS/MS). The samples were homogenized with HCl, extracted with n-pentane, derivatized with 2-nitrobenzaldehyde, and the derivative was extracted with ethyl acetate. After solvent exchange to 10% acetonitrile in water containing 0.1% acetic acid, the samples were analyzed using a 2.1 mm x 150 mm C18 column eluted with 2 mM ammonium formate in water/methanol (40:60). Semicarbazide was formed during the dry heating of commercial azodicarbonamide-containing flours at temperatures of 150-200 degrees C reaching levels of 0.2 mg/kg. Similar levels of semicarbazide were found in the crusts of breads made from azodicarbonamide-treated flour.     

Determination of inorganic tin in biological samples by hydride generation-atomic absorption spectrometry after silica gel cleanup

A method is described for the determination of inorganic tin in biological samples by hydride generation-atomic absorption spectrometry (HG-AAS). A sample is extracted with ethyl acetate after addition of HCl and NaCl. The concentrated extract is passed through a silica gel column. The column is washed with ethanol, water, and 0.2N HCl successively, and then inorganic tin is eluted with 2N HCl and measured by HG-AAS. Recoveries from fish muscle spiked with 0.1 micrograms/g Sn4+ are 78.9 +/- 4.2% (average +/- standard deviation, n = 5). The detection limit is 0.01 micrograms/g as Sn.     

设施菜田土壤pH和初始C/NO3– 对反硝化产物比的影响

【目的】设施菜田土壤反硝化作用是N₂O排放和氮素损失的重要途径。本研究通过室内厌氧培养试验,在不同pH和初始C/NO₃–条件下,比较设施菜田土壤反硝化氮素气体排放及产物比的变化特征。【方法】以设施菜田土壤为研究对象,通过添加一定量低浓度的酸碱溶液调节土壤pH分别为酸性、中性和碱性条件,调节后的实测pH分别为5.63、6.65和7.83;同时以谷氨酸钠作为有效性碳,除未添加有效性碳作为对照处理 (CK) 外,其他有效性碳与硝酸盐 (C/NO₃–) 的比值分别调节为5∶1、15∶1和30∶1,三种pH条件下均设置 4 个 C/NO₃– 水平,每个水平3次重复。利用自动连续在线培养系统 (Robot系统),在厌氧条件下监测不同处理土壤产生的 N₂O、NO、N₂和CO₂浓度的动态变化,通过计算N₂O/(N₂O + NO + N₂)指数估算反硝化过程N₂O的产物比。【结果】增加土壤的pH能显著减少设施菜田土壤N₂O和NO的产生量,酸性 (pH 5.63) 土壤的N₂O、NO产生量峰值在不同初始C/NO₃– 比下均显著高于中性 (pH 6.65) 和碱性 (pH 7.83) 土壤 (P < 0.05)。中性和碱性土壤在高C/NO₃– 下有利于减少反硝化过程N₂O的产生,而酸性土壤条件下差异并不显著。中性土壤条件下增加有机碳含量会降低NO产生量,而在酸性和碱性土壤上有机碳的添加对NO产生量没有显著影响。土壤pH和初始C/NO₃– 比对土壤N₂O的产生有极显著的交互效应 (P < 0.001)。酸性和中性土壤上添加有机碳能够显著增加土壤N₂的产生速率 (P < 0.05),且与对照相比,不同pH的土壤添加有机碳后均显著促进反硝化过程中N₂O向N₂的转化。在不同初始C/NO₃– 下碱性土壤的CO₂产生量显著高于酸性和中性土壤,同时与对照相比,添加有机碳显著增加了土壤的CO₂产生量 (P < 0.05)。酸性土壤的N₂O产物比在不同初始C/NO₃– 下均极显著高于碱性土壤 (P < 0.01),且不同初始C/NO₃– 下的土壤N₂O产物比随pH的增加显著下降,二者呈极显著线性负相关关系 (P < 0.01)。【结论】土壤pH降低是设施菜田土壤N₂O和NO排放量较高的重要原因。而且,增加初始土壤有效碳含量促进了土壤的反硝化损失,并在中性和碱性土壤中N₂O的产生量减少。土壤pH升高和初始C/NO₃– 增加均降低了产物比,但增加了土壤反硝化作用速率。在利用N₂O排放通量和产物比估算土壤反硝化氮素损失时,土壤pH和有效碳含量是必须考虑的两个重要因素。     

Analysis of bisphenol A and alkylphenols in cereals by automated on-line solid-phase extraction and liquid chromatography tandem mass spectrometry

An on-line solid-phase extraction (SPE) following a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method was established for the simultaneous analysis of bisphenol A (BPA), nonylphenol (NP), and octylphenol (OP) in cereals (including rice, maize, and wheat). The target compounds were extracted by acetonitrile, purified by an automated on-line SPE cartridge, and analyzed by LC-MS/MS under the negative-ion mode. Mean recoveries fortified at three concentration levels ranged from 81.6 to 115.7%, and the coefficient of variation ranged from 4.6 to 19.9% (n = 6). The limits of quantification (LOQs) of the method were 0.5, 0.5, and 0.25 μg/kg for BPA, NP, and OP, respectively, in both rice and maize, while the LOQs in wheat were 0.5, 1.25, and 0.5 μg/kg for BPA, NP, and OP, respectively. This method was applied in the analysis of rice, maize, and wheat from a local market. As a result, NP occurred in all cereal samples at the concentration range of 9.4-1683.6 μg/kg and BPA was detected in a few samples.     

Determination of bisphenol A in canned foods by immunoaffinity chromatography, HPLC, and fluorescence detection

Bisphenol A (BPA) concentrations were determined in canned beverages, fruits, vegetables, and fat-containing foodstuffs bought in Austrian supermarkets. The analysis method consisted of sol-gel immunoaffinity chromatography followed by high-performance liquid chromatography with fluorescence detection. With one exception traces of BPA were detected in all samples. BPA recovery strongly depended on the food matrix, ranging from 27% in goulash to 103% in a lemon soft drink. The results obtained allow a more realistic picture of the BPA exposure caused by cans with an epoxy resin protective coating because--in contrast to several previous studies--only those fractions of the can contents that are actually consumed were analyzed. BPA concentrations ranging from 0.1 ng/mL (lemon soft drink) to 38 ng/g (ready-to eat soup from Thailand) were significantly lower than the European Union migration limit of 0.6 mg of BPA/kg of food.     

Optimization of a liquid chromatography-tandem mass spectrometry method for quantification of the plant lignans secoisolariciresinol, matairesinol, lariciresinol, and pinoresinol in foods

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of the four major enterolignan precursors [secoisolariciresinol, matairesinol, lariciresinol, and pinoresinol] in foods. The method consists of alkaline methanolic extraction, followed by enzymatic hydrolysis using Helix pomatia (H. pomatia) beta-glucuronidase/sulfatase. H. pomatia was selected from several enzymes based on its ability to hydrolyze isolated lignan glucosides. After ether extraction samples were analyzed and quantified against secoisolariciresinol-d8 and matairesinol-d6. The method was optimized using model products: broccoli, bread, flaxseed, and tea. The yield of methanolic extraction increased up to 81%, when it was combined with alkaline hydrolysis. Detection limits were 4-10 microg/(100 g dry weight) for solid foods and 0.2-0.4 microg/(100 mL) for beverages. Within- and between-run coefficients of variation were 6-21 and 6-33%, respectively. Recovery of lignans added to model products was satisfactory (73-123%), except for matairesinol added to bread (51-55%).     

Oxidative degradation of bisphenol a by crude enzyme prepared from potato

When crude enzymes prepared from some vegetables and fruits were incubated with bisphenol A (2,2-bis(4-hydroxyphenyl)propane, BPA) at 37 degrees C, BPA was oxidized by crude enzymes from potato, eggplant, and lettuce. The crude enzyme prepared from potato (Solanum tuberosum) had the strongest oxidative activity for BPA. Its optimal temperature and pH were 40-45 degrees C and 8.0, respectively. More than 95% of BPA was oxidized after the incubation with potato enzyme for 60 min. BPA gave two oxidation products besides insoluble compounds during the oxidation by potato enzyme. The oxidation products were identified to be 4[1-(4-hydroxyphenyl)-1-methyl-ethyl]-benzene-1,2-diol and 4[1-(4-hydroxyphenyl)-1-methyl-ethyl]-benzene-1,3-diol. Enzymatically oxidized BPA lost the estrogen-like activity to enhance the growth of human breast cancer (MCF-7) cells.     

Migration of bisphenol A from polycarbonate baby and water bottles into water under severe conditions

The isotope dilution headspace solid-phase microextraction and gas chromatography-mass spectrometry method for bisphenol A (BPA) developed previously was used successfully in a BPA migration study at 70 degrees C of polycarbonate baby and reusable water bottles recently sold in Canada by using the whole bottles instead of pieces cut from the bottles. Migration of BPA from the PC bottles heated at 70 degrees C was found to increase over the time in the quadratic equations. Migration levels of BPA in water varied from 228 to 521 microg L (-1) or from 0.26 to 0.90 microg cm (-2) after being heated at 70 degrees C for 6 days. The average migration rates of BPA from the PC bottles into water at 70 degrees C ranged from 1.84 to 4.83 ng cm (-2) h (-1).     

One-step derivatization and preconcentration microextraction technique for determination of bisphenol A in beverage samples by gas chromatography-mass spectrometry

A simple technique based on ultrasound-assisted emulsification microextraction in situ derivatization (USAEME-ISD) is proposed for the one-step derivatization, extraction, and preconcentration of bisphenol A (BPA) in beverage samples prior to gas chromatography-mass spectrometry (GC-MS) analysis. BPA was in situ derivatized with acetic anhydride and simultaneously extracted and preconcentrated by using USAEME. Variables affecting the extraction efficiency of BPA were evaluated. Under optimal experimental conditions, the detection limit (LOD) was 38 ng L(-1) with a relative standard deviation (RSD) value of 11.6%. The linear working range was 100-1250 ng L(-1), and the coefficient of estimation (r(2)) of the calibration curve was ≥0.9971. The robustness of the proposed methodology was probed by developing a recovery study at two concentrations (125 and 500 ng L(-1)) over different beverage samples. This study led to a satisfactory result achieving recoveries of ≥82%, which showed acceptable robustness for determination of nanograms per liter of BPA in samples of food safety interest.     

Lipophilic toxins analyzed by liquid chromatography-mass spectrometry and comparison with mouse bioassay in fresh, frozen, and processed molluscs

The search for alternative methods to the mouse bioassay (MBA) has intensified over recent years. The present work analyzes seven different species of shellfish (clams, small scallops, small clams, mussels, oysters, cockles, and edible whelks) in fresh, frozen boiled, and canned presentations using liquid chromatography-mass spectrometry (LC-MS/MS), and the results are compared with the same samples analyzed through MBA. The toxins studied were OA, DTX1, DTX2, YTX, PTX2, and AZA1, which are legislated in the EU, and SPX1, which is not regulated yet. Consistent results between LC-MS/MS and MBA were found in 69% of the samples, whereas 26% of MBA showed "false-positive" results with respect to the toxins analyzed. No "false negatives" were observed. The possibility of LC-MS/MS as an alternative or complementary technique to MBA is discussed.     

Ion-pair reverse phase liquid chromatographic determination of sodium acifluorfen in feed

Ion-pair reverse phase liquid chromatography (LC) and UV detection at 280 nm have been used to determine sodium acifluorfen (sodium-5-[2-chloro-4-(trifluoromethyl)-phenoxy]-2-nitrobenzoate), an experimental diphenyl ether herbicide, in dog feed. Sodium-5-(2,4-dichlorophenoxy)-2-nitrobenzoate is used as the internal standard. The feed is homogenized in 0.01N HCl, followed by ethyl acetate extraction, and centrifugation. The organic layer is removed and evaporated and the residue is reconstituted in methanol and filtered before LC analysis (mobile phase methanol-water (58 + 42), 0.005M in tetrabutylammonium phosphate and 0.045M in (NH4)2HPO4, at pH 7.4). The ion-pair technique offers a high degree of control over the retention characteristics of the herbicide and internal standard. The use of the internal standard permits precise and accurate quantitation and substantially reduces analysis time compared with the external standard method.     

Acrylamide in foods: occurrence,sources, and modeling

Acrylamide in food products-chiefly in commercially available potato chips, potato fries, cereals, and bread-was determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Samples were homogenized with water/dichloromethane, centrifuged, and filtered through a 5 kDa filter. The filtrate was cleaned up on mixed mode, anion and cation exchange (Oasis MAX and MCX) and carbon (Envirocarb) cartridges. Analysis was done by isotope dilution ([D(3)]- or [(13)C(3)]acrylamide) electrospray LC-MS/MS using a 2 x 150 mm (or 2 x 100 mm) Thermo HyperCarb column eluted with 1 mM ammonium formate in 15% (or 10% for the 2 x 100 mm column) methanol. Thirty samples of foods were analyzed. Concentrations of acrylamide varied from 14 ng/g (bread) to 3700 ng/g (potato chips). Acrylamide was formed during model reactions involving heating of mixtures of amino acids and glucose in ratios similar to those found in potatoes. In model reactions between amino acids and glucose, asparagine was found to be the main precursor of acrylamide. Thus, in the reaction between nitrogen-15 (amido)-labeled asparagine and glucose, corresponding (15)N-labeled acrylamide was formed. The yield of the model reaction is approximately 0.1%.     

Characterization of new bisphenol a metabolites produced by CD1 mice liver microsomes and S9 fractions

Bisphenol A [2,2-bis(4-hydroxyphenyl)propane] (BPA) is a widely used industrial chemical resulting in occupational and consumer exposure. BPA possesses weak estrogenomimetic activity and can be cytotoxic, though the underlying mechanisms of its toxicity toward cells are not completely understood. The metabolism of BPA by CD1 mice liver microsomal and S9 fractions was investigated. Nine metabolites were isolated and characterized using HPLC and mass spectrometry. Many of these metabolites were characterized for the first time in mammals, namely isopropyl-hydroxyphenol (produced by the cleavage of BPA), a bisphenol A glutathione conjugate, glutathionyl-phenol, glutathionyl 4-isopropylphenol, and BPA dimers. Most of these metabolites apparently share a common metabolic pathway, for which considerable evidence supports the hypothesis of the production of a reactive intermediate, and also helps explain BPA cytotoxicity.     

Photodegradation of hexythiazox in different solvent systems under the influence of ultraviolet light and sunlight in the presence of TiO2, H2O2, and KNO3 and identification of the photometabolites

The photodegradation of the carboxamide acaricide hexythiazox in three different solvent systems (aqueous methanolic, aqueous isopropanolic, and aqueous acetonitrilic solutions) in the presence of H(2)O(2), KNO(3), and TiO(2) under ultraviolet (UV) light (λ(max) ≥ 250 nm) and sunlight (λ(max) ≥290 nm) has been assessed in this work. The kinetics of photodecomposition of hexythiazox and the identification of photoproducts were carried out using liquid chromatography-mass spectrometry. The rate of photodecomposition of hexythiazox in different solvents followed first-order kinetics in both UV radiation and natural sunlight, and the degradation rates were faster under UV light than under sunlight. Hexythiazox was found to be more efficiently photodegraded in the presence of TiO(2) than in the presence of H(2)O(2) and KNO(3). Two major photoproducts were separated in pure form using column chromatography and identified according to IR, (1)H NMR, and mass spectral information as cyclohexylamine and 5-(4-chlorophenyl)-4-methylthiazolidin-2-one. Another nine photoproducts were identified according to LC-MS/MS spectral information. The plausible photodegradation pathways of hexythiazox were proposed according to the structures of the photoproducts.     

NaCl浓度对SBBR同步脱氮及N2O释放的影响

盐度是影响生物脱氮过程的重要因素。盐度增加会导致生物硝化和反硝化过程中N_2O的产生并释放。该文以添加NaCl的生活污水为研究对象,采用固定填料序批式生物膜反应器(sequencing batch biofilm reactor,SBBR),考察了不同NaCl浓度(0、5、10、15和20g/L)对SBBR脱氮性能及N_2O释放的影响。结果表明,试验NaCl浓度范围内,SBBR出水COD稳定在40～60mg/L。硝化过程NO_2~-/NO_3~-随NaCl浓度增加而增加。NaCl浓度≤10g/L时,NH_4~+-N去除率大于95%,N_2O产率由4.08%(NaCl浓度为0)增至6.72%(NaCl浓度为10 g/L)。NaCl浓度为20 g/L时,驯化后SBBR内平均NH_4~+-N去除率为70%,平均N_2O产率为13.60%。无添加NaCl时,N_2O主要产生于硝化阶段的AOB好氧反硝化过程,SBBR内缺氧区有助于减少N_2O释放;高NaCl浓度条件下,N_2O主要产生于AOB好氧反硝化过程和内源同步反硝化过程,高盐度加剧内源反硝化阶段NO_2~-和N_2O之间电子竞争,抑制N_2O还原,其活性抑制性能与电子受体和初始C/N有关。与硝态氮还原速率和亚硝态氮还原速率相比,氧化亚氮还原速率受NaCl抑制最为明显,是导致高盐度条件下N_2O释放量增加的重要因素。