LC–MS/MS multi-method for mycotoxins after single extraction,with validation data for peanut,pistachio, wheat,maize, cornflakes,raisins and figs

Mycotoxin analysis is usually carried out by high performance liquid chromatography after immunoaffinity column cleanup or in enzyme-linked immunosorbent assay tests. These methods normally involve determination of single compounds only. EU legislation already exists for the aflatoxins, ochratoxin A and patulin in food, and legislation will come into force for deoxynivalenol, zearalenone and the fumonisins in 2007. To enforce the various legal limits, it would be preferable to determine all mycotoxins by routine analysis in different types of matrices in one single extract. This would also be advantageous for HACCP control purposes. For this reason, a multi-method was developed with which 33 mycotoxins in various products could be analysed simultaneously. The mycotoxins were extracted with an acetonitrile/water mixture, diluted with water and then directly injected into a LC–MS/MS system. The mycotoxins were separated by reversed-phase HPLC and detected using an electrospray ionisation interface (ESI) and tandem MS, using MRM in the positive ion mode, to increase specificity for quality control. The following mycotoxins could be analysed in a single 30-min run: Aflatoxins B₁, B₂, G₁ and G₂, ochratoxin A, deoxynivalenol, zearalenone, T-2 toxin, HT-2 toxin, α-zearalenol, α-zearalanol, β-zearalanol, sterigmatocystin, cyclopiazonic acid, penicillic acid, fumonisins B₁, B₂ and B₃, diacetoxyscirpenol, 3- and 15-acetyl-deoxynivalenol, zearalanone, ergotamin, ergocornin, ergocristin, α-ergocryptin, citrinin, roquefortin C, fusarenone X, nivalenol, mycophenolic acid, alternariol and alternariol monomethyl ether. The limit of quantification for the aflatoxins and ochratoxin A was 1.0 µg kg^?1 and for deoxynivalenol 50 µg kg^?1. The quantification limits for the other mycotoxins were in the range 10–200 µg kg^?1. The matrix effect and validation data are presented for between 13 and 24 mycotoxins in peanuts, pistachios, wheat, maize, cornflakes, raisins and figs. The method has been compared with the official EU method for the determination of aflatoxins in food and relevant FAPAS rounds. The multi-mycotoxin method has been proven by the detection of more than one mycotoxin in maize, buckwheat, figs and nuts. The LC–MS/MS technique has also been applied to baby food, which is subject to lower limits for aflatoxin B₁ and ochratoxin A, ergot alkaloids in naturally contaminated rye and freeze-dried silage samples.     

The Limiting Density of Unit Root Test Statistics: A Unifying Technique

In this note we introduce a simple principle to derive a constructive expression for the density of the limiting distribution, under the null hypothesis, of unit root statistics for an AR(1)-process in a variety of situations. We consider the case of unknown mean and reconsider the well-known situation where the mean is zero. For long-range dependent errors we indicate how the principle might apply again. We also show that in principle the method also works for a near unit root case. Weak convergence and subsequent Karhunen-Loeve expansion of the weak limit of the partial sum process of the errors plays an important role, along with the evaluation of a certain normal type integral with complex mean and variance. For independent and long range dependent errors this weak limit is ordinary and fractional Brownian motion respectively.
AMS 1991 subject classification. Primary 62M10; secondary 62E20.     

LC-MS/MS multi-method for mycotoxins after single extraction, with validation data for peanut, pistachio, wheat, maize, cornflakes, raisins and figs.

Mycotoxin analysis is usually carried out by high performance liquid chromatography after immunoaffinity column cleanup or in enzyme-linked immunosorbent assay tests. These methods normally involve determination of single compounds only. EU legislation already exists for the aflatoxins, ochratoxin A and patulin in food, and legislation will come into force for deoxynivalenol, zearalenone and the fumonisins in 2007. To enforce the various legal limits, it would be preferable to determine all mycotoxins by routine analysis in different types of matrices in one single extract. This would also be advantageous for HACCP control purposes. For this reason, a multi-method was developed with which 33 mycotoxins in various products could be analysed simultaneously. The mycotoxins were extracted with an acetonitrile/water mixture, diluted with water and then directly injected into a LC-MS/MS system. The mycotoxins were separated by reversed-phase HPLC and detected using an electrospray ionisation interface (ESI) and tandem MS, using MRM in the positive ion mode, to increase specificity for quality control. The following mycotoxins could be analysed in a single 30-min run: Aflatoxins B1, B2, G1 and G2, ochratoxin A, deoxynivalenol, zearalenone, T-2 toxin, HT-2 toxin, alpha-zearalenol, alpha-zearalanol, beta-zearalanol, sterigmatocystin, cyclopiazonic acid, penicillic acid, fumonisins B1, B2 and B3, diacetoxyscirpenol, 3- and 15-acetyl-deoxynivalenol, zearalanone, ergotamin, ergocornin, ergocristin, alpha-ergocryptin, citrinin, roquefortin C, fusarenone X, nivalenol, mycophenolic acid, alternariol and alternariol monomethyl ether. The limit of quantification for the aflatoxins and ochratoxin A was 1.0 microg kg(-1) and for deoxynivalenol 50 microg kg(-1). The quantification limits for the other mycotoxins were in the range 10-200 microg kg(-1). The matrix effect and validation data are presented for between 13 and 24 mycotoxins in peanuts, pistachios, wheat, maize, cornflakes, raisins and figs. The method has been compared with the official EU method for the determination of aflatoxins in food and relevant FAPAS rounds. The multi-mycotoxin method has been proven by the detection of more than one mycotoxin in maize, buckwheat, figs and nuts. The LC-MS/MS technique has also been applied to baby food, which is subject to lower limits for aflatoxin B1 and ochratoxin A, ergot alkaloids in naturally contaminated rye and freeze-dried silage samples.     

Effect of viscoelasticity on drop dynamics in 5:1:5 contraction/expansion microchannel flow

Recently, we reported how viscoelasticity affects drop dynamics in a microchannel flow using the finite element-front tracking method (FE-FTM). In this work, we investigate drop dynamics for a wider range of parameters: viscosity ratio between droplet and medium (χ), capillary number (Ca), droplet size, and fluid elasticity. The Oldroyd-B model is adopted as the constitutive equation for the viscoelastic fluid. We observe that the drop deformation in a microfluidic channel is dependent on Ca, which is more pronounced for smaller χ values. The present work shows that viscoelasticity plays an important role in drop dynamics with increasing χ values for Newtonian droplet in viscoelastic medium, which can be attributed to high normal stress developed in narrow film thickness between droplet and channel for higher χ values. We also study circulation problem inside droplets, which is important in practice, such as in droplet reactor application. The present work shows that circulation intensity is enhanced with decreasing χ values. We find that the relevance of viscoelastic effects on internal circulation is dependent on χ values, and the circulation intensity is distinctively decreased with increasing elasticity for high χ values for Newtonian droplet in viscoelastic medium. We expect that the present work be helpful not only in controlling droplets but also to improve our physical insight on drop dynamics in microchannel flows.     

Mixing processes in the cavity transfer mixer: A thorough study

In many industrial applications, the quality of mixing between different materials is fundamental to guarantee the desired properties of products. However, properly modeling and understanding polymer mixing presents noticeable difficulties, because of the variety and complexity of the phenomena involved. This is also the case with the Cavity Transfer Mixer (CTM), an add‐on to be mounted downstream of existing extruders, to improve distributive mixing. The present work proposes a fully three‐dimensional model of the CTM: a finite element solver provides the transient velocity field, which is used in the mapping method implementation to compute the concentration field evolution and quantify mixing. Several simulations are run assessing the impact on mixing of geometrical and functioning parameters. In general, the number of cavities per row should be limited and the cavity size rather big to guarantee good mixing quality. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1034–1048, 2018     

Control of gold surface diffusion on si nanowires

Silicon nanowires (NW) were grown by the vapor-liquid-solid mechanism using gold as the catalyst and silane as the precursor. Gold from the catalyst particle can diffuse over the wire sidewalls, resulting in gold clusters decorating the wire sidewalls. The presence or absence of gold clusters was observed either by high angle annular darkfield scanning transmission electron microscopy images or by scanning electron microscopy. We find that the gold surface diffusion can be controlled by two growth parameters, the silane partial pressure and the growth temperature, and that the wire diameter also affects gold diffusion. Gold clusters are not present on the NW side walls for high silane partial pressure, low temperature, and small NW diameters. The absence or presence of gold on the NW sidewall has an effect on the sidewall morphology. Different models are qualitatively discussed. The main physical effect governing gold diffusion seems to be the adsorption of silane on the NW sidewalls.     

A novel,efficient route for the crosslinking and creep improvement of high modulus and high strength polyethylene fibres

A new route is presented for the chemical crosslinking of solution‐spun, ultra‐drawn Ultra‐High‐Molecular‐Weight Polyethylene (UHMW‐PE) fibres. UHMW‐PE fibres with a range of draw ratio's, Young's moduli and tensile strengths were impregnated with a radical initiator using supercritical carbon dioxide as a carrier. After impregnation, the drawn fibres were crosslinked with ultra‐violet light and fibres with a high gel content (> 90%) were obtained. It was found that the chemical crosslinking strongly reduces the plateau creep rate of the fibres and that the threshold stress for irreversible creep is enhanced. Simultaneously, the high Young's modulus and the high tensile strength of the drawn fibres are preserved which illustrates that the long term properties of the fibres (i. e. creep) are improved without a large sacrifice short term mechanical properties such as Young's modulus.     

Adjoint sensitivity analysis for a three-dimensional photochemical model: application to Southern California

An adjoint method was used to investigate the sensitivity of peak ozone at selected sites in Southern California to nearly 900 model inputs including surface emissions, reaction rate coefficients, dry deposition velocities, boundary conditions, and initial conditions. Simulations showed large changes in ozone and ozone sensitivities at three sites investigated between summers 1987 and 1997 due to emission reductions. However, only small changes in ozone and ozone sensitivities were predicted between 1997 and 2010. Sensitivities of the differences in ozone between simulations with different emission scenarios were calculated and compared to sensitivities of ozone in each simulation. In some cases, the sensitivities of ozone differences were smaller than those of ozone itself, but in other cases, such as when the sensitivityto NOx emissions changed sign, sensitivities of differences were larger. The adjoint method was most useful for determining when and where model inputs affect, or have the potential to affect, an ozone response. For example, the method was used to plot the spatial distribution of important emission source regions to 1-hour versus 8-hour peak ozone. Changes in the distribution and sign of the adjoint function for emitted species revealed changes in the area of influence of pollutant emissions on peak ozone due to emission controls. The adjoint method provides useful information complementary to that obtained from forward sensitivity analysis methods.