Volume 69, Issue 3

A simple and sensitive amperometric method for the detection of glyphosate based on a porous copper nanowire electrode is presented. The porous nanowires were fabricated simply by a one-step electrodeposition using hydrogen bubbles generated during the deposition to produce pores. These porous nanowires provided a 1.4 times larger surface area than a porous copper film. After the fabrication process the porous copper nanowires can be applied directly as a working electrode with the same custom-built flow cell. The detection was carried out by measuring the oxidation signal of copper; this increased with the concentration of glyphosate due to dissolution of the copper from the electrode. Under optimal conditions, the responses of the sensor were linear between 0.010-5.0 μmol L −1 , with a limit of detection of 10.0 nmol L −1 (S/N = 3). The large surface area of the electrode minimised the corrosion effect, as observed by the remarkably stable response (95 injections of 0.20 μmol L −1 of glyphosate were possible). When applied in order to detect glyphosate in fresh fruit and vegetable samples, the concentrations were found in the range of non-detectable to (0.104 ± 0.005) μmol L −1 . These results indicated that the fabrication process can be used to produce a new form of working electrode for glyphosate detection.

This work describes a novel methodology for the recognition of brandies based on direct injection of a raw sample followed by GC-MS analysis. Direct injection was chosen for its simplicity and the fact that the composition of the samples analysed remains unchanged compared to original brandy. The repeatability of the analytical procedure was evaluated by a comparison of the peak areas for randomly selected compounds obtained from 10 parallel measurements. A novel chemometric procedure was investigated in order to separate the samples studied on the basis of their geographical origin, processing technology or maturation time. In this procedure, a principal component analysis was applied to full chromatograms to select the time interval that shows the significant differences between the samples studied. It was shown that the chromatogram recorded at 36-39 min bore the maximal differences, hence it could be used to classify the brandy samples. The chromatographic peaks found within this time interval were identified and their peak areas determined. These compounds could be used as specific markers for determining geographical origin or processing technology.

A method for the determination of the moisture content in cigarette papers using solvent extraction followed by gas chromatographic analysis was developed. Optimal extraction conditions, including the agitation method, solvent and extraction time, as well as optimal gas chromatographic parameters, such as the internal standard, were investigated. The maximum degree of moisture extraction was achieved when samples were soaked in 20 mL of ethanol containing 0.5 mL L −1 of isopropanol as an internal standard for 50 min under ultrasonic agitation. The method showed good linearity over the concentration range from 0.26 mass % to 10 mass % of the moisture content with a correlation coefficient of 0.99998. The recovery (102.1-109.3 %) and precision (relative standard deviation: 1.64 %) of the method were examined by analyzing various cigarette paper samples. The method was successfully applied to different types of paper and it exhibits superior accuracy and high efficiency compared with the existing methods of moisture determination.

Protein glycation leads to the formation of advanced glycation end-products (AGEs), which contribute to the pathogenesis of diabetic complications. The structure-activity relationship of dietary flavonoids for inhibiting the glycation of bovine serum albumin (BSA) in vitro was subjected to a detailed investigation. The structure-activity relationship revealed that: 1) the hydroxylation on ring B of the flavones enhanced the inhibition and the hydroxyl groups at the C-5 and C-7 positions of flavones favoured the inhibition; 2) the optimal number of hydroxyl groups on ring B of the flavonols was one (at the C-3 position) and the methylation of flavonols weakened the inhibition; 3) the methoxylation at the C-6 position and methylation at C-4' position of genistein clearly enhanced the inhibition; 4) the hydroxyl groups at the C-5 and C-7 positions of flavanones were in favour of the inhibition; 5) the glycosylation of flavonoids significantly weakened the inhibition. Obvious linear affinity-activity relationships exist between the BSA-flavonoid interaction and flavonoids as BSA glycation inhibitors (R 2 = 0.76585). The flavonoids with a higher affinity to BSA exhibited a stronger inhibition of the glycation of BSA.

Biogas production is proposed as an alternative approach to using natural rubber Hevea brasiliensis latex serum, a major waste product from the production of concentrated latex. To make the most efficient use of the reactor size, the addition of macroalgal biomass as a co-substrate to the fermentation system was investigated. The biogas yield of latex serum as a single substrate was (398 ± 14) L per kg of volatile solids added (VSA). For the co-digestion system, algae mixed with serum were investigated at wet mass ratios of Chaetomorpha sp. to Ulva intestinalis to serum at 3 : 0 : 1, 2 : 0 : 2, 1 : 0 : 3, 0 : 1 : 3, 0 : 2 : 2 and 0 : 3 : 1. The co-digestion system with latex serum at 2 to 3 out of 4 parts produced the highest biogas yields within the range of 422-460 L kg −1 of VSA. Other parameters such as carbon to nitrogen mass ratio, total solids content and initial pH value were investigated at the constant ratio of 1 : 3 of Chaetomorpha sp. to latex serum, and the parameter settings of 15, 10.5 % and 7, respectively, were close to optimal, with an (888 ± 155) L kg −1 of VSA cumulative gas yield. The methane yield of the optimised system over 45 days was (197 ± 16) L kg −1 of VSA and the reduction in COD was (40 ± 4) %. Latex serum, whether alone or co-digested with algae in biogas production, appears to be promising for the management of waste in concentrated latex production.

This paper focuses on the adhesion and biofilm formation potential of cellulolytic yeast Trichosporon cutaneum CCY 30-5-10 on solid cellophane from a novel perspective. First, physicochemical characterisation of the cells and carrier (cellophane) was performed to evaluate the effect of different culture media (complex vs mineral) on yeast cell adhesion. (Un)favourable adhesion conditions were predicted using the thermodynamic approach. Next, the ability of the cells to colonise the carrier under the above conditions was quantified and the biofilm structure was characterised using image analysis. The approaches described were found suitable to predict and experimentally verify favourable (cell-solid) adhesion, i.e. the hydrophobic and low electron-donor nature of cellophane together with hydrophobic cells (obtained when cultivated in a complex culture medium) were found to have a major impact in defining successful yeast adhesion with subsequent biofilm formation.

Cross-linked enzyme aggregates (CLEA) of Aspergillus oryzea α-amylase (AoAA) and Aspergillus niger glucoamylase (AnGA) were prepared using glutaraldehyde and dextran polyaldehyde as crosslinkers. The maximum activity recoveries for glutaraldehyde cross-linking were 21.8 % and 41.2 %, respectively. The addition of a proteic feeder (bovine serum albumin) exhibited a negative effect on the activity recoveries for both enzymes. Dextran polyaldehyde was used as a cross-linking agent instead of glutaraldehyde to reduce the activity losses. As a result, an activity recovery of 60.0 % was obtained for Aspergillus oryzea α-amylase. On the other hand, no activity recovery was observed for Aspergillus niger glucoamylase due to the latter enzyme’s affinity for dextran.

The dissolution kinetics of cerussite was investigated using methanesulphonic acid (MSA) as an alternative leaching reagent. The effects of particle size, stirring speed, acid concentration, and reaction temperature on the lead dissolution rate were determined. The dissolution process followed the kinetic law of the shrinking-core model, and a corresponding mixed control model was found suitable for representing the rate-controlling step. The mixed kinetic model comprised two stages: surface chemical reaction (283 K to 303 K) and diffusion through the product layer (303 K to 323 K). The activation energies of these sequential stages were 43.20 kJ mol −1 and 17.20 kJ mol −1 , respectively. The corresponding dissolution kinetic equations are also presented to describe the dissolution reaction. The results indicated that methanesulphonic acid could be used as an effective leaching reagent for extracting lead from cerussite minerals.

On basis of earlier experimental experience, the transfer of protons in salts of the organic cation-inorganic anion type occurs primarily through directional arrangement of the anion-anion type short hydrogen bonds. The submitted work presents the preparation of quaternary pyridinium salts of inorganic hydrogen anions in the absence of solvent molecules in their crystal structure. These substances can form only the above-described anion-anion type hydrogen bonds; in addition, the absence of solvate anions increases the stability of the prepared compounds. A total of six substituted pyridinium salts were prepared, four of which have not been described yet: 1,2,4,6-tetraphenylpyridinium perchlorate, 1-benzyl-2,4,6-trimethylpyridinium perchlorate, 1,4-dimethylpyridinium hydrogen sulphate, 1,4-dimethylpyridinium dihydrogen phosphate, 1,4-dimethylpyridinium hydrogen sulphate, and 1,2-dimethyl-5-ethylpyridinium dihydrogen phosphate. Three of these substances were characterised by X-ray structural analysis: 1,2,4,6- tetraphenylpyridinium perchlorate crystallises in the orthorhombic system, space group Pbca; 1- benzyl-2,4,6-trimethylpyridinium perchlorate crystallises in the monoclinic system, space group P2 1 /c; and 1,4-dimethylpyridinium dihydrogen phosphate crystallises in the monoclinic system, space group C2/c. This structure contains an oriented anion network bond by short anion-anion type hydrogen bonds with the donor acceptor lengths of 2.567(3) Å and 2.557(3) Å and thus fulfils the requirements of a good proton conductor.

A novel UV absorption material of squaric acid (SA) anion (C 4 O 4 2- ) intercalated layered double hydroxides (LDHs) was successfully synthesized by the co-precipitation method. After intercalation, the interlayer distance of MgAl-SA-LDHs increased to 1.04 nm compared to those of MgAl-CO 3 - LDHs and SA anions present in form of a monolayer in the interlayer of LDHs. Thermal stability of SA clearly enhanced by the intercalation and the suppression of the deintercalation ability of MgAl-SA-LDHs was superior to that of 4-hydroxy-3-methoxybenzoic acid intercalated LDHs. The results of UV-DRS indicate the potential application of MgAl-SA-LDHs as UV absorbers.

The electrolytic deposition of nanosized Cu/Ni-Cu multilayer coatings on a paraffin-impregnated graphite substrate was performed from an electrolyte consisting of sulphate salts of the above metals and a complex-forming agent, sodium citrate. The multilayer Cu/Ni-Cu coatings were prepared using the potentiostatic method, in which the potential was alternately pulsed between the reduction potentials of the components. Suitable deposition potentials were selected from the polarisation curves. The presence of the thin films was confirmed by atomic absorption spectroscopy (after dissolution) and by optical microscopy. The resulting images show a layered structure of Cu/Ni-Cu coatings formed by Cu, Ni and/or Ni-Cu layers.

An efficient synthesis of bis(indolyl)methanes was developed. Bis(indolyl)methanes were synthesized starting from various aromatic aldehydes with indole under microwave irradiation and solvent-free conditions (85-98 %). Solid support SiO 2 was found to possess favorable catalytic and dispersancy parameters for the condensation reaction. Moreover, novel bis(indolyl)methanes containing an isoxazole ring were synthesized via this method in excellent yields (> 94 %) using 3-substituted isoxazole-5-carbaldehydes and indole.

An efficient mixed reagent for direct synthesis of symmetrical carboxylic anhydrides from carboxylic acids has been prepared. Carboxylic acids are converted to anhydrides using triphenylphosphine/ trichloroisocyanuric acid under mild reaction conditions at room temperature. Short reaction time, excellent yields of products, low cost, availability of reagents, simple experimental procedure, and easy work-up of the products are the main advantages of the presented method.

2,3-dimethoxy-5-hydroxymethyl-6-methyl-1,4-benzoquinone (V) was prepared with a 75 % yield by means of a reaction sequence starting from 2,3,4,5-tetramethoxytoluene via Blanc chloromethylation reaction, Kornblum oxidation, NaBH 4 reduction and ceric ammonium nitrate oxidation. The procedure is operationally simple and amenable to gram-scale synthesis.

The reaction of phenylacetonitrile in supercritical methanol and ethanol in a system containing a small volume of water was studied. The effects of various operating conditions, such as reaction temperature, reaction time, the mole ratio of phenylacetonitrile/water/methanol or ethanol on the product yield were systematically investigated. The optimal yield of methyl phenylacetate for phenylacetonitrile in supercritical methanol in a system containing a small volume of water was 70 % at 583 K and 2.5 h. The optimal yield of ethyl phenylacetate for phenylacetonitrile in supercritical ethanol with a small volume of water was 80 % at 583 K and 1.0 h. At the same time, a feasible mechanism was proposed for phenylacetonitrile in supercritical methanol and ethanol in a system containing a small volume of water.