Rapid determination of fumonisins B1 and B2 in corn by liquid chromatography-tandem mass spectrometry with ultrasonic extraction

A simple, sensitive, and reliable analytical method is developed for the rapid determination of fumonisin B(1) and fumonisin B(2) in corn by high-performance liquid chromatography-positive electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). Fumonisin B(1) and fumonisin B(2) are extracted from corn with methanol-water (3:1, v/v) by means of ultrasonic extraction, and directly injected into an LC-MS-MS system after centrifugation. Fumonisin B(1) and fumonisin B(2) are separated on a Zorbax Eclipse XDB-C(18) column with a solution of methanol-water-formic acid as the mobile phase. The method is validated with respect to linearity, accuracy, precision, specificity, and stability. Moreover, the method was applied to real samples and demonstrated to be suitable for the determination of fumonisin B(1) and fumonisin B(2) in corn. The total time required for the analysis of one sample was ~30 min.     

Evaluation of silica- and sepharose-based immunoaffinity sorbents for sample cleanup in determination of fumonisins B1 and B2 in corn products

Anti-fumonisin B1 polyclonal antibodies were isolated from the serum of rabbits, immobilized onto the surface of glutaraldehyde-activated silica or Sepharose CL-4B particles, and placed into empty small plastic solid-phase extraction cartridges. The immobilized antibodies were evaluated for their ability to retain fumonisin B1 and fumonisin B2. Cartridge capacity and elution conditions were determined, and the results were compared to those obtained with a commercially available cartridge. The cartridges, which were tested for their effectiveness to isolate the fumonisins from extracts of corn flour and nacho chips, detected fumonisins down to levels of about 20 ng/g. However, additional cleanup was required for detection at lower concentrations. With the use of a strong anion-exchange cartridge as a preliminary cleanup before immunoaffinity chromatography, the detection limit reached 2-5 ng/g in the products tested. The silica sorbent material exhibited strong interactions with the fumonisins, requiring acidified ethanol-water mixtures for elution and resulting in an additional degree of selectivity in isolating fumonisins from sample extracts. The silica-based immunoaffinity cartridges were successfully reused more than 10 times; the Sepharose-based cartridges were less robust. Liquid chromatography with fluorescence detection was used after prechromatographic derivatization with o-phthaldialdehyde-mercaptoethanol.     

Effect of binary solvent composition on phenol extraction from aqueous solutions

Partition factors D between an apolar solvent-ketone or ketone-ketone binary mixture and water have been determined for a series of p-alkylphenols. The effects of the composition of a binary solvent and phenol hydrophobicity on the partition factor have been studied. Empirical relationships adequately describing the partition factor isotherms versus the mole fraction of the active component of the binary organic solvent have been found and discussed.     

Determination of fumonisins B1 and B2 in corn and corn flakes by liquid chromatography with immunoaffinity column cleanup: collaborative study.

A liquid chromatographic (LC) method for the determination of fumonisins B1 (FB1) and B2 (FB2) in corn and corn flakes was collaboratively studied by 23 laboratories, which analyzed 5 blind duplicate pairs of each matrix to establish the accuracy, repeatability, and reproducibility characteristics of the method. Fumonisin levels in the corn ranged from <0.05 (blank) to 1.41 microg/g for FB1 and from <0.05 to 0.56 microg/g for FB2, whereas in the corn flakes they ranged from <0.05 to 1.05 microg/g for FB1 and from <0.05 to 0.46 microg/g for FB2. The method involved double extraction with acetonitrile-methanol-water (25 + 25 + 50), cleanup through an immunoaffinity column, and LC determination of the fumonisins after derivatization with o-phthaldialdehyde. Relative standard deviations for the within-laboratory repeatability (RSDr) of the corn analyses ranged from 19 to 24% for FB1 and from 19 to 27% for FB2; for the corn flakes analyses, RSDr ranged from 9 to 21 % for FB1 and from 8 to 22% for FB2. Relative standard deviations for the between-laboratories reproducibility (RSDR) of the corn analyses ranged from 22 to 28% for FB1 and from 22 to 30% for the FB2; for corn flakes analyses, RSDR ranged from 27 to 32% for FB1 and from 26 to 35% for FB2. Mean recoveries of FB1 and FB2 from corn spiked with FB1 at 0.80 microg/g and with FB2 at 0.40 microg/g were 76 and 72%, respectively; for corn flakes spiked at the same levels recoveries were 110 and 97% for FB1 and FB2, respectively. HORRAT ratios for the analyses of corn ranged from 1.44 to 1.53 for FB1 and from 0.96 to 1.48 for FB2, whereas for corn flakes they ranged from 1.60 to 1.82 for FB1 and from 1.39 to 1.68 for FB2.     

Application of molecularly imprinted polymers to determine B1, B2, and B3 fumonisins in cereal products

The aim of this study was to develop an analytical method for qualitative and quantitative determination of the B₁, B_2, and B₃ fumonisins in cereal products. A LC coupled to an IT‐MS was used as the analytical instrument. The AFFINIMIP FumoZON Molecularly Imprinted Polymer SPE cartridges (Polyintell) were used to isolate fumonisins from the analyzed samples and the clean‐up step. Statistical parameters evaluated in some validation experiments were as follows: mean recovery 95–106%, precision <17% (expressed as recovery RSD). The developed method was used to determine fumonisins in 49 cereals (42 maize‐based and seven wheat‐based products). In most cases, concentrations of the studied compounds found in the analyzed samples were low. The highest total concentration of the B₁, B₂, and B₃ fumonisins was found in maize flour samples (range, 26–1102 μg/kg, mean 498 μg/kg).     

Robotic automated clean-up for detection of fumonisins B1 and B2 in corn and corn-based feed by high-performance liquid chromatography

A high-performance liquid chromatography (HPLC) system with fluorescence detection and an automated on-line solid-phase extraction procedure for fumonisins B1 and B2 in corn and corn-based products is described. Different amounts of strong anion-exchange, C18 and end-capped C18 (C(18 ec)) silicas were tested for sample clean-up. Various HPLC parameters were analyzed. The best methodology was found to be extraction with acetonitrile-water and clean up on C(18 ec) disposable extraction cartridges. The system has the advantage of running in an unattended mode of operation and allows processing of 40 samples without system refuel, performing clean-up, o-phthaldialdehyde derivatization, injection and fumonisin detection by fluorescence detection linked to a computer integrator for automated data processing. Recoveries were performed with corn and corn-based feed samples (n=3) spiked with 0.1, 0.5, 1.0, 5.0 and 10 microg/g. Average recoveries for corn and corn-based feed were, respectively, 92.6 and 88.3% with relative standard deviations (RSDs) of 5.04 and 6.22%, for fumonisin B1 and 91.2 and 89.0% with RSDs of 5.84 and 7.88% for fumonisin B2. Detection limits (S/N=3) for corn and corn-based feed were approximately 0.03 microg/g for fumonisin B1 and 0.05 microg/g for fumonisin B2     

温度对松木屑气化液体产物组成的影响

利用傅里叶变换红外光谱(FT-IR)和气质联用(GC/MS)技术,研究了松木屑在400~900℃气化液体产物的主要组成成分和液体产物主要化学组成的来源与转化随气化温度变化的规律。结果表明,松木屑低温气化液体产物主要为酮、呋喃和愈创木酚等含氧化合物。随气化温度升高,液体产物的组成发生显著变化,400~ 500℃主要发生愈创木酚向酚类化合物的转变,500~600℃主要发生酮、呋喃向酚类化合物的转变,600~700℃主要发生酚类向茚和PAHs (多环芳烃)的转变,700~900℃主要发生酚类化合物向PAHs的转变,900℃液体产物的组成为大分子量的PAHs。     

Determination of fumonisins B1 and B2 in corn by liquid chromatography/mass spectrometry with immunoaffinity column cleanup: single-laboratory method validation

A single-laboratory method validation was conducted to establish the effectiveness of an immunoaffinity column cleanup procedure followed by liquid chromatography/mass spectrometry (LCIMS) for the determination of fumonisins B1 and B2 (FBI + FB2) in corn. The test portion is extracted with acetonitrile-methanol-water (25 + 25 + 50). The extract is filtered, diluted with phosphate-buffered saline solution, and applied to an immunoaffinity column. FB1 + FB2 are removed with methanol and directly determined by reversed-phase LC with MS detection using selected-ion monitoring of 2 characteristic ions in each case. Test portions of blank corn samples were spiked with a mixture of FB1 + FB2 to give total levels of 200 and 500 ng/g, respectively. Recoveries of both FB1 and FB2 from spiked samples averaged 90.4-101%. Based on results for spiked raw corn (triplicates at 2 levels), the relative standard deviation for repeatability ranged from 2.8 to 7.1%. The accuracy of the method was demonstrated by analysis of Food Analysis Performance Assessment Scheme (FAPAS) test material. The method was also applied to a small survey of processed corn products such as corn chips, cornflakes, and popcorn.     

Determination of fumonisins B1 and B2 in various maize products by a combined SAX + C18 column and immunoaffinity column

Fumonisins B1 and B2 were determined in 42 samples of different maize products from the Swedish market by 2 different methods based on cleanup steps using an immunoaffinity column and a combination of SAX + C18 columns, respectively. A simple "precipitation step" was included before the samples were added to the main column(s), giving less column clogging, fewer interfering peaks, and better recoveries for the different sample matrixes. Recovery, repeatability, and results from the survey showed comparable results with the methods. The limit of detection for both methods was 5 micrograms/kg for fumonisin B1 and 10 micrograms/kg for fumonisin B2. All 7 maize chips analyzed and 6 of 8 popcorn samples contained fumonisins (B1 + B2) with averages of 180 and 115 micrograms/kg, respectively. All other samples except a maize flour sample contained little or no fumonisins.     

Separation of fission and corrosion products from boric acid solutions by solvent extraction

Extractive purification of boric acid from radioactive corrosion and fission products dissolved in aqueous solutions modelling nuclear reactor coolants has been studied. Aliphatic 1,3-diols containing 8 and 9 carbon atoms per molecule were used as extractants fro boric acid. The behaviour of some representative corrosion and fission products as well as various factors affecting their distribution between the organic and aqueous phases have been investigated under the conditions of boric acid extraction. Conditions for the effective separation of boric acid from most of the radioactive contaminants are presented.     

Effect of solvent and temperature on solution-crystallized terfenadine

The aim of this work was to understand the crystallization process of terfenadine in solution.Cooling of saturated solutions prepared at 50 °C at different temperatures, evaporating the solvent from nearly saturated solutions at a certain temperature, and exposing ethanol solutions of terfenadine to water vapour atmosphere were the techniques used for obtaining terfenadine specimens. The characterization of these specimens was carried out by thermal microscopy, differential thermal analysis, thermogravimetry and powder X-ray diffraction. Crystalline phases, amorphous solids, and solvates were identified. For the solvents used in the present study, the crystallinity degree of terfenadine decreases from ethanol-water to ethanol and from this to methanol. Decreasing the temperature promotes the formation of amorphous solid material; at low temperatures, methanol and ethanol solvates are also formed.Desolvation, following the terfenadine aggregation process in solution accounts for the different behaviour found for the solvents and for the effect of temperature on the structure. The role of the solvent as structure-mediator is explained on the grounds of the values previously published for the enthalpy of solution of terfenadine in the solvents under study.     

Effect of organic solvent concentration on radioimmunoassay of aflatoxin B1

The effect of acetone and methanol contents in an aqueous casein-buffer solution pipetted with aflatoxin B1 into radioimmunoassay procedure, on some parameters of radioimmunochemical determination of aflatoxin B₁ has been studied. These organic solvents lower an antiserum titer and value of the zero specific binding, and at higher concentrations make worse the detection limit and the accuracy of radioimmunoassay. However, in radioimmunoassay of food extracts containing subresidual levels of aflatoxin, it could be advantageous to add the extract volume to the organic solvent concentration of 60%.     

Effect of the temperature on the composition and ratio of hydrolysis products of 1,2-dichlorotetramethyldisilane

The hydrolysis of 1,2-dichlorotetramethyldisilane was studied at different temperatures. At reduced temperatures, the hydrolysis gave permethylcyclo(oxadisilanes) [(Me₂Si)₂O]_n (n = 2 and 3) and α,ω-dihydroxypermethyloligo(oxadisilanes) HO[(SiMe₂)₂O]_mH (m = 1–5). The formation of the latter was proved by the GC-MS method. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 722–724, April, 2006.     

Determination of fumonisins B1 and B2 in Portuguese maize and maize-based samples by HPLC with fluorescence detection

Fumonisins B₁ (FB₁) and fumonisin B₂ (FB₂) are the main members of a family of mycotoxins produced by Fusarium verticillioides, Fusarium proliferatum, and other fungi species of the section Liseola. The present work shows the results of comparative studies using two different procedures for the analysis of fumonisins in maize and maize-based samples. The studied analytical methods involve extraction with methanol/water, dilution with PBS, and clean-up through immunoaffinity columns. Two reagents (o-phthaldialdehyde and naphthalene-2,3-dicarboxaldehyde) were studied for formation of fluorescent derivatives. The separation and identification were carried out by high-performance liquid chromatography with fluorescence detection. The optimized method for analysis of fumonisins in maize involved extraction with methanol/water (80:20), clean-up with an immunoaffinity column, and derivatization with naphthalene-2,3-dicarboxaldehyde (NDA). The limit of detection was 20 μg kg⁻¹ for FB₁ and 15 μg kg⁻¹ for FB₂. Recoveries of FB₁ and FB₂ ranged from 79% to 99.6% for maize fortified at 150 μg kg⁻¹ and 200 μg kg⁻¹, respectively, with within-day RSDs of 3.0 and 2.7%. The proposed method was applied to 31 samples, and the presence of fumonisins was found in 14 samples at concentrations ranging from 113 to 2,026 μg kg⁻¹. The estimated daily intake of fumonisins was 0.14 μg kg⁻¹ body weight per day.     

Determination of fat in dairy products using pressurized solvent extraction

Gravimetric fat data were obtained for a wide range of dairy products with fat contents ranging from 0.5 to 83% using pressurized solvent extraction at elevated temperatures and pressure (80-120 degrees C; 10.3 MPa). Extraction performance was sensitive to solvent composition, temperature, and sample matrix. By optimizing solvent mixtures, sample-solvent contact times of 8-10 min were sufficient for high recoveries from all products tested. The most successful solvents with regard to speed of extraction, selectivity, and recovery (average recovery, %) were various mixtures of hexane (or petroleum ether)-dichloromethane-methanol for dried cream (99.8%), dried whole milk (99.6%), dried buttermilk (98.2%), dried skim milk (97.0%), dried whey protein concentrate (97.5%), casein (95.0%), and caseinate (102.1%); petroleum ether-acetone-ethanol or petroleum ether-acetone-isopropanol for cheddar-type cheese (99.4%); petroleum ether-acetone for butter (99.9%); petroleum ether-acetone-isopropanol for cream (100.3%); and petroleum ether-isopropanol for liquid milks (99.0%). Relative standard deviations for repeatability were obtained for dried whole milk (0.2%), dried whey protein concentrate (0.7%), cheese (0.3%), butter (0.1%), and ultraheat treated (UHT) milk (0.7%). Solvent removal and drying of extracts with a heated block evaporator saved time compared with conventional drying ovens. Estimated savings in labor (50-75%) and solvents (80%) were substantial compared with the manual Mojonnier methods.     

Development of a new analytical method for the determination of fumonisins B1 and B2 in food products based on high performance liquid chromatography and fluorimetric detection with post-column derivatization

A sensitive and selective analytical method was developed for the quantitative determination of fumonisins B(1) and B(2) in maize-based foods for direct human consumption. The method, based on high-performance liquid chromatography and fluorescence detection, presents a rapid and automated on-line post-column derivatization, performed with o-phtalaldehyde and N,N-dimethyl-2-mercaptoethylamine. Several factors affecting the separation and detection of fumonisins were investigated, including mobile phase composition, column features, derivatization agent flow-rate and both the excitation and the emission wavelengths. Optimal fluorescence detection was obtained by using a lambda(exc) of 343 nm and a lambda(em) of 445 nm. Under the optimized experimental conditions, a complete separation of fumonisins was obtained in less than 13 min by using a C(18) column and a gradient elution at 0.8 mL/min with methanol and 0.1M phosphate buffer at pH 3.15. The limits of detection for FB(1) and FB(2) were 4 and 5 microg/L corresponding to 5 and 6 microg/kg in matrix. Each fumonisin was determined in the range 40-320 microg/L that correspond to 50-400 microg/kg in matrix. The necessary requirements for accuracy, reproducibility and sensitivity were fulfilled and recovery values ranged from 87 to 94% for FB(1) and from 70 to 75% for FB(2) in cornflake samples at three fortification levels in the range 100-300 microg/kg. The potential of this method, combined with a simple clean-up procedure, was assessed by the measurements of FB(1) and FB(2) in maize-based products, such as maize flour, "polenta", tortillas and cookies.     

Effect of composition of the solvent on the selectivity of competitive hydrogenation of 2-methyl-3-butene-2-ol and 1-hexene

The selectivity of competitive hydrogenation of 2-methyl-3-butene-2-ol and 1-hexene on 5% Pt on silica gel catalyst at 20°C and atmospheric pressure was investigated, and the effect of changes in the composition of the solvent on the selectivity of hydrogenation was examined. Three solvent systems have been used: methanol-water, 1-heptanol-cyclohexane and ethanol-cyclohexane mixtures. The causes underlying changes in the selectivity of hydrogenation with changing composition of the solvent are discussed.

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2--3--2- 1- 5% Pt 20°C . . 1- . .

     

Analysis of fumonisins B(1), B(2) and B(3) in corn-based baby food by pressurized liquid extraction and liquid chromatography/tandem mass spectrometry

A sensitive and reliable method using pressurized liquid extraction (PLE) and liquid chromatography (LC)/electrospray ionization (ESI) tandem mass spectrometry with a triple quadrupole (QqQ) analyzer has been developed for the analysis of fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) in corn-based baby foods. Influence of several extraction parameters that affect PLE efficiency such as temperature, pressure, solvent extraction, number of cycles and dispersant/clean-up agents were studied. The selected PLE operating method was: 3g of sample was packed into 11 ml stainless-steel cell and fumonisins were extracted with methanol at 40 degrees C, 34 atm in one cycle of 5 min at 60% flush. The analytes were ionized in ESI operating with positive ion mode and identified by selecting two monitoring transitions, permitting quantification and confirmation in a single injection. Recoveries ranged from 68% to 83% at fortification levels of 200 microg kg(-1) with relative standard deviation (RSD) from 4% to 12%. The limits of quantification were from 2 microg kg(-1) for FB(1) and FB(2), and 5 microg kg(-1) for FB(3), which are below the maximum residue level established by the European Union legislation in infant formulas. The proposed method was successfully applied to the analysis of twenty seven samples of baby food products collected from different markets, and one positive sample with a content of 15.9 microg kg(-1) for FB(1), 9.2 microg kg(-1)for FB(2) and 5.8 microg kg(-1) for FB(3) was obtained. Given the simplicity and potential of the proposed procedure, its application for safety control is recommended.     

溶剂特性对淖毛湖煤加氢液化中间产物反应行为的影响

为探究溶剂特性对煤加氢液化中间产物反应行为的影响,以新疆淖毛湖煤作为原料,四氢萘、循环溶剂及十氢萘作为供氢溶剂,在高压搅拌釜中进行直接加氢液化实验,并运用电子顺磁共振手段分析了中间产物-沥青质的自由基浓度的变化。结果表明,四氢萘溶剂中沥青质随反应温度的升高在大量生成的同时又被转化,产率从290℃的12.92%到350℃的最大34.13%再到430℃的15.98%;循环溶剂中沥青质产率先持续上升,290℃即有31.89%,400℃达到最大47.96%,之后由于结焦反应降低至33.90%。十氢萘溶剂中沥青质产率变化趋势与四氢萘一致。三种溶剂中沥青质自由基浓度的变化趋势相同,均在350℃达到最大值,分别是1.778×10¹⁸、2.323×10¹⁸和1.930×10¹⁸/g,整体上看循环溶剂数值要高于四氢萘,十氢萘介于两者之间。而四氢萘及循环溶剂中沥青质的g值在2.00323-2.00403,变化趋势与液化气体产物中CO_x含量变化相吻合。     

Spectrophotometric solvent extraction studies of 2-mercaptopyridine-1-oxide and uranyl ion complex

The complex formed by uranyl ion with 2-mercaptopyridine-1-oxide (thione) is studied by spectrophotometry. At pH 4.5 and 25 degrees the only complex formed is UO(2)(thione)(3)(-). The conditional stability constant of this complex is 2.6 x 10(12). Tributyl phosphate is used for the extraction of the complex from the aqueous phase and the extraction constant is 8.9 x 10(12). The use of the reagent for the separation and determination of uranyl ion is elaborated.