Selective Hydrogenation of Biomass-Derived Succinic Acid: Reaction Network and Kinetics

The conversion of bio-based succinic acid (SA) to the value-added chemicals 1,4-butanediol (BDO), γ-butyrolactone (GBL), and tetrahydrofuran (THF) can replace the corresponding petrochemical production routes to achieve a sustainable process. The reaction network for aqueous-phase catalytic hydrogenation of succinic acid over a supported Re-Pd catalyst was identified and the reaction kinetics was determined. With the developed kinetic model, the composition of the product mixture regarding the desired products (BDO, GBL, THF) can be described as a function of educt concentration, temperature, and pressure. The maximum BDO yield was achieved at high pressure and low temperature, while low pressure and high temperature favored GBL and THF production.     

Efficient vector radiative transfer calculations in vertically inhomogeneous cloudy atmospheres

Accurate radiative transfer calculations in cloudy atmospheres are generally time consuming, limiting their practical use in satellite remote sensing applications. We present a model to efficiently calculate the radiative transfer of polarized light in atmospheres that contain homogeneous cloud layers. This model combines the Gauss-Seidel method, which is efficient for inhomogeneous cloudless atmospheres, with the doubling method, which is efficient for homogeneous cloud layers. Additionally to reduce the computational effort for radiative transfer calculations in absorption bands, the cloud reflection and transmission matrices are interpolated over the absorption and scattering optical thicknesses within the cloud layer. We demonstrate that the proposed radiative transfer model in combination with this interpolation technique is efficient for the simulation of satellite measurements for inhomogeneous atmospheres containing one homogeneous cloud layer. For example, the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) measurements in the oxygen A band (758-773 nm) and the Hartley-Huggins ozone band (295-335 nm) with a spectral resolution of 0.4 nm can be simulated for these atmospheres within 1 min on a 2.8 GHz PC with an accuracy better than 0.1%.     

Co-occurrence of ochratoxin A and citrinin in unprocessed cereals established during a three-year investigation period

The aim of this study was to investigate ochratoxin A (OTA) and citrinin (CIT) co-occurrence in different unprocessed cereals (n = 189) originating from Croatia during a three-year investigation period (2014–2016) using validated enzyme immunoassay (ELISA) methods. CIT and OTA were determined in 49% and 7% of samples, respectively. Significantly higher (p < 0.05) overall mean concentrations were determined for CIT (66.8 ± 76.0 µg/kg) in comparison to OTA (5.2 ± 1.1 µg/kg). Based on the analysis of all investigated cereals, CIT was found about 15 times more frequently than OTA and in similarly (15-fold) higher concentrations, irrespective of the cultivation year. The results revealed a moderately positive correlation between OTA and CIT concentrations in maize (r_s = 0.44) and wheat (r_s = 0.59), whereas in barley and oat this correlation (p > 0.01) was not significant.     

Uncertainty of Trypsin Inhibitor Activity Measurement of Legume Crops Using Microtiter Plate Method

Trypsin inhibitors could limit utilization of legumes in human nutrition, but they could also have beneficial health effects. The objective of this study was to measure trypsin inhibitor activity (TIA) of different legumes using microtiter plate method and to identify factors that contribute to uncertainty of TIA measurement. TIA measurements were performed on seeds of faba bean, pea, common vetch, soybean, and common bean cultivars. The significant effect of legume crop on TIA measurement uncertainty was confirmed with P = 0.045. Certain sources of measurement uncertainty were related with the content of trypsin inhibitors (Tis) in legume seeds. In respect to that, significant effect of level of sample dilution (P ? 0.001) was confirmed. Significant influence of the repeated absorbance measurement of sample reaction mixture on uncertainty of TIA measurement was identified (P ? 0.001), and it took 60% of overall TIA measurement uncertainty for soybean cultivars. TIA of soybean cultivars exceeded 90 TUI/mg. Repeated absorbance measurement of positive control reaction mixture took 70% of TIA measurement uncertainty of cultivars with TIA lesser than 4.5 TUI/mg. Graduated cylinder used for preparation of the final sample solutions took the range from 45 to 90% of overall TIA measurement uncertainty of the cultivars whose TIA were in the middle of previously mentioned. The uncertainty of TIA measurement of legume crops was not studied before; thus, this study pointed out that acquiring insight into factors contributing to uncertainty of TIA measurement could give directions for improvement of TIA testing if microtiter plate method is used.     

Ochratoxin A in raw materials and cooked meat products made from OTA-treated pigs

The aim of this study was to determine ochratoxin A (OTA) concentrations in the raw materials and cooked meat products made from pigs sub-chronically exposed to OTA. The treated animal group (n = 5) was administered with 300 μg OTA/kg of feed for 30 days, whereas the control group (n = 5) was left untreated. OTA concentrations were quantified using immunoassay (ELISA) and high performance liquid chromatography with fluorescence detection (HPLC-FD). OTA concentration was the highest in the kidney, followed by the lungs, liver, blood, spleen, heart, and adipose tissue. As for the final meat products, the highest average OTA concentration was detected in black pudding sausages (14.02 ± 2.75 μg/kg), then in liver sausages (13.77 ± 3.92 μg/kg), while the lowest was found in pâté (9.33 ± 2.66 μg/kg). The results pointed out that a sub-chronic pig exposure leads to the accumulation of OTA in raw materials and consequently in meat products, whose level of contamination is directly dependent on OTA contents in raw materials used for their production.     

A Model for the Phosphorus Dynamics of VPO Catalysts during the Selective Oxidation of n‐Butane to Maleic Anhydride in a Tubular Reactor

A model for the phosphorus dynamics in vanadium‐phosphorus oxide (VPO) catalysts for the oxidation of n‐butane to maleic anhydride was developed. According to the model, reversible sorption processes determine the phosphorus content of the catalyst. Simulations reveal that several phenomena can be successfully described. If no phosphorus is added to the reactant feed, the catalytic activity increases until runaway occurs. With addition of a proper amount of phosphorus, the loss can be compensated while excessive phosphorus addition results in complete catalyst deactivation. Adjusting the model parameters to experimental data may result in a model that can be used to optimize the performance of maleic anhydride reactors.     

Citrinin in cereals and feedstuffs coming from Croatia and Bosnia & Herzegovina

The aim of this study was to investigate the occurrence of citrinin in different cereals (n = 341) and feedstuffs (n = 67) coming from farms and feed factories established in Croatia and Bosnia & Herzegovina. The highest mean citrinin concentration (103 ± 102 µg/kg) was observed in cereals sampled in Bosnia & Herzegovina during 2014, although significantly different levels between the two countries were not observed. Across the cereal samples, the maximal citrinin concentration was determined in wheat (429 µg/kg), while across the feedstuffs, the highest concentration was found in pig feed (63 µg/kg). Despite of the increased citrinin levels found in some samples, especially wheat, the obtained values cannot be compared against the maximum limits, since no such levels are stipulated under the applicable legislation. But, given that data on citrinin are very scarce, they can serve as an indicator of cereal and feed contamination in this part of Europe.     

Cl2 Adsorption and Desorption over Ordered Mesoporous Carbon Materials as an Indicator for Catalytic Phosgene Formation

The presented work evaluates the implementation of adsorption and desorption experiments with Cl₂ over carbon materials towards the development of more active and stable catalysts for industrial phosgene synthesis. By using a soft templating method as a tool, ordered mesoporous carbon materials with tunable porosity, surface area, and degree of graphitization were synthesized and utilized as model system. The Cl₂ adsorption/desorption properties of these materials were studied and compared to commercial activated carbon. To draw correlations between Cl₂ adsorption/desorption behavior and catalytic performance, the materials were further tested in the phosgene formation in a plug flow reactor. However, the chemical reaction of Cl₂ with carbon during the adsorption/desorption experiment hinders a direct correlation.     

Xenobiotic clenbuterol in food producing male pigs: Various tissue residue accumulation on days after withdrawal

Using enzyme-linked immunosorbent assay (ELISA) and liquid chromatography tandem mass spectrometry (LC-MS/MS) the concentrations of clenbuterol (ng/g) were shown to be highest in choroid/pigmented retinal epithelium (choroid/PRE) (499.59±26.36ng/g), followed by hair (fair colored) (207.76±86.88ng/g), liver (25.06±16.72ng/g) and kidney (6.88±3.52ng/g) after 28 days of oral clenbuterol administration in a growth-promoting dose (10μg/kg BW, twice daily) to food producing male pigs, with a high correlation coefficient between the two methods for all study matrices (r=0.8800-0.9999). In the liver as an alimentary tissue and regulatory matrix for the control of clenbuterol abuse, the maximal allowed concentration of 0.5ng/g was achieved in liver tissue (0.40±0.12ng/g) on day 14 and in the kidney (0.28±0.10ng/g) on day 7 after treatment withdrawal. In contrast, the concentration of residual clenbuterol in choroid/PRE (57.49±6.13ng/g) and hair (68.36±3.35ng/g) recorded on day 14 of withdrawal was 143- and 170-fold that measured in the liver, with a similar ratio persisting on day 35 of withdrawal (164:1 and 183:1, respectively). These findings indicated a high accumulation potential of clenbuterol residues in the hair and choroid/PRE as compared with the liver and kidney, pointing to the pig choroid/PRE and hair as useful new matrices in the control of clenbuterol abuse as a growth promotant in food production, especially after prolonged withdrawal.     

Clenbuterol residues in pig muscle after repeat administration in a growth-promoting dose

The aim of this study was to determine the level of clenbuterol residues in muscle tissue of pigs after repeat administration in a growth-promoting dose. An anabolic dose of clenbuterol (20 μg/kg body mass per day) was administered orally to experimental group (n = 12) for 28 days, whereas control animals (n = 3) were left untreated. Clenbuterol treated pigs were randomly sacrificed (n = 3) on days 0, 3, 7 and 14 of treatment discontinuation and clenbuterol residues determined in muscle tissue. Determination of residual clenbuterol was by enzyme-linked immunosorbent assay (ELISA) as a screening method and liquid chromatography tandem mass spectrometry (LC-MS/MS) as a confirmation method. The highest clenbuterol content in the muscle of treated animals was recorded on day 0 of treatment cessation (4.40 ± 0.37 ng/g) and significantly (p < 0.05) exceeded the maximum residue limit (MRL) of 0.1 ng/g. On day 3 of withdrawal, it was 0.49 ± 0.22 ng/g and on day 7 0.10 ± 0.02 ng/g (at MRL); on day 14 of treatment discontinuation, clenbuterol content was below the limit of detection (< 0.1 ng/g) in all samples. Administration of clenbuterol as a growth promoter in pig production could lead to residues in meat for human consumption up to 7 days after treatment discontinuation.