Sabino Aurelio Bufo

Effects of organic amendment and herbicide treatment on soil microbial biomass

Abstract The interactive effects of vermi-compost from sewage sludge and either the sulfonylurea herbicide, rimsulfuron, or the imidazolinone herbicide, imazethapyr, on some soil biochemical and microbiological properties were investigated. The herbicides were applied at field and 10-fold field rates. Both herbicides exerted a detrimental effect on soil microbial biomass and its biochemical properties. Even though the effect of both herbicides on soil microbial biomass was not detectable at the field rate, some significant influences on acid and alkaline phosphatase were observed. The higher rate of herbicide application impaired the observed microbial parameters to a greater degree. The detrimental effects seemed to be reduced by organic amendments. Among the studied microbial characteristics, the specific respiration quotient was particularly reliable and sensitive in determining the influence of herbicides on the soil microbial biomass. In this paper a new synthetic index, specific hydrolytic activity (qFDA), for assessing microbial activity in reply to xenobiotic treatments is proposed.

Drought-induced variations of water relations parameters in Olea europaea

The effects of water stress on water potential components, tissue water content, mean elastic modulus and the osmoregulation capacity of olive (Olea europaea L. cv. Coratina) leaves was determined. Artificial rehydration of olive leaf tissues altered the P-V relationships so that a plateau phenomenon occurred. Points in the P-V curve in the region affected by the plateau, generally up to −0.5 MPa, were corrected for all the samples analyzed. In the corrected P-V relationship, an osmotic adjustment was found in drought-stressed leaf tissues. Osmotic potentials at full turgor (Ψ0 (sat)) and osmotic potential at turgor-loss (Ψ0 (TVT)) decreased from −2.06±0.01 MPa and −3.07±0.16 MPa in controls to −2.81±0.03 MPa and −3.85±0.12 MPa in most stressed plants. Osmotic adjustment values obtained from the P-V curves agreed with those obtained using an osmometer. An active osmotic adjustment of 1.42 MPa was also observed in 1–4 mm- diameter roots. Mannitol is the main carbohydrate involved in osmotic potential decrease in all treatments. The maximum elastic modulus increased from 11.6±0.95 MPa in the controls to 18.6±0.61 MPa in the most stressed plants.

Optimizing separation conditions for riboflavin, flavin mononucleotide and flavin adenine dinucleotide in capillary zone electrophoresis with laser-induced fluorescence detection

A method was developed for the quantitative determination of riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), using free solution capillary zone electrophoresis in uncoated fused-silica capillaries with laser-induced fluorescence (LIF) detection. Various factors influencing the separation and detection of flavin vitamers were investigated, including pH (5.5-10.5), concentration and nature of the run buffer (phosphate, borate and carbonate), applied voltage (15-30 kV), temperature (15-30 degrees C) and injection time. Optimal resolution and detection were obtained with a pH 9.8, 30 mM aqueous phosphate buffer at 15 degrees C and 30 kV of applied voltage. LIF detection was obtained with a He-Cd laser source using an excitation wavelength at 442 nm and lambda(em) > or = 515 nm. Riboflavin could be determined in the concentration ranges 0.5-350 microg/l with a rather low detection limit (LOD) down to 50 amol. The LODs of FAD and FMN were slightly higher, 300 and 350 amol, respectively. Combined with a simple clean-up procedure, the practical utility of this method is illustrated by the measurements of flavin derivates in foods and beverages, such as wines, milk, yoghurt and raw eggs.

Photolysis and hydrolysis of rimsulfuron

The degradation in the liquid phase of rimsulfuron and its commercial 250 g kg−1 WG formulation (Titus®) was investigated. Photolysis reactions were carried out at 25 °C by a high-pressure mercury arc (Hg-UV) and a solar simulator (Suntest), while the hydrolysis rate was determined by keeping aqueous buffered samples in the dark. The effects of solvent and water pH on reaction kinetics were studied, and the results compared to literature data. Photoreactions of the commercial product in organic solvents were faster than pure rimsulfuron. Under simulated sunlight in water, the half-life for the photolysis reaction ranged from one to nine days at pH 5 and 9, respectively. The hydrolysis rate was as high as the photolysis rate, but decreased on increasing water pH. The main metabolite identified in neutral and alkaline conditions as well as in acetonitrile was N-[(3-ethylsulfonyl)-2-pyridinyl]-4,6-dimethoxy-2-pyridinamine, while N-(4,6-dimethoxy-2-pyrimidinyl)-N-[(3-(ethylsulfonyl)-2-pyridinyl)]urea and minor metabolites prevailed in acidic conditions. © 1999 Society of Chemical Industry

Establishing the occurrence of major and minor glucosinolates in Brassicaceae by LC-ESI-hybrid linear ion-trap and Fourier-transform ion cyclotron resonance mass spectrometry

Glucosinolates (GLSs) are sulfur-rich plant secondary metabolites which occur in a variety of cruciferous vegetables and among various classes of them, genus Brassica exhibits a rich family of these phytochemicals at high, medium and low abundances. Liquid chromatography (LC) with electrospray ionization in negative ion mode (ESI-) coupled to a hybrid quadrupole linear ion trap (LTQ) and Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS) was employed for the selective and sensitive determination of intact GLSs in crude sample extracts of broccoli (Brassica oleracea L. Var. italica), cauliflower (B. oleracea L. Var. Botrytis) and rocket salad (Eruca sativa L.) with a wide range of contents. When LTQ and FTICR mass analyzers are compared, the magnitude of the limit of detection was ca. 5/6-fold lower with the FTICR MS. In addition, the separation and detection by LC-ESI-FTICR MS provides a highly selective assay platform for unambiguous identification of GLSs, which can be extended to lower abundance (minor) GLSs without significant interferences of other compounds in the sample extracts. The analysis of Brassicaceae species emphasized the presence of eight minor GLSs, viz. 1-methylpropyl-GLS, 2-methylpropyl-GLS, 2-methylbutyl-GLS, 3-methylbutyl-GLS, n-pentyl-GLS, 3-methylpentyl-GLS, 4-methylpentyl-GLS and n-hexyl-GLS. The occurrence of these GLSs belonging to the saturated aliphatic side chain families C(4), C(5) and C(6), presumably formed by chain elongation of leucine, homoleucine and dihomoleucine as primary amino acid precursors, is described. Based on their retention behavior and tandem MS spectra, all these minor compounds occurring in plant extracts of B. oleracea L. Var. italica, B. oleracea L. Var. Botrytis and E. sativa L. were tentatively identified.

In Vitro Antifungal Activity of Burkholderia gladioli pv. agaricicola against Some Phytopathogenic Fungi

The trend to search novel microbial natural biocides has recently been increasing in order to avoid the environmental pollution from use of synthetic pesticides. Among these novel natural biocides are the bioactive secondary metabolites of Burkholderia gladioli pv. agaricicola (Bga). The aim of this study is to determine antifungal activity of Bga strains against some phytopathogenic fungi. The fungicidal tests were carried out using cultures and cell-free culture filtrates against Botrytis cinerea, Aspergillus flavus, Aspergillus niger, Penicillium digitatum, Penicillium expansum, Sclerotinia sclerotiorum and Phytophthora cactorum. Results demonstrated that all tested strains exert antifungal activity against all studied fungi by producing diffusible metabolites which are correlated with their ability to produce extracellular hydrolytic enzymes. All strains significantly reduced the growth of studied fungi and the bacterial cells were more bioactive than bacterial filtrates. All tested Bulkholderia strains produced volatile organic compounds (VOCs), which inhibited the fungal growth and reduced the growth rate of Fusarium oxysporum and Rhizoctonia solani. GC/MS analysis of VOCs emitted by strain Bga 11096 indicated the presence of a compound that was identified as 1-methyl-4-(1-methylethenyl)-cyclohexene, a liquid hydrocarbon classified as cyclic terpene. This compound could be responsible for the antifungal activity, which is also in agreement with the work of other authors.

Isocratic separations of closely-related mono- and disaccharides by high-performance anion-exchange chromatography with pulsed amperometric detection using dilute alkaline spiked with barium acetate

Mixtures of closely related mono- and disaccharides may be efficiently separated by high-performance anion-exchange chromatography (HPAEC) only when relatively dilute alkaline eluents are employed (i.e., < 20 mM NaOH). The main drawbacks of these eluent solutions are (i) column regeneration between runs, (ii) poor reproducibility of the retention times, and (iii) the need for post-column base addition for enhancing sensitivity. Here, we describe some examples of isocratic separations of carbohydrates by HPAEC coupled with pulsed amperometric detection (PAD) accomplished by carbonate-free alkaline eluents (i.e., 5-20 mM NaOH) obtained upon addition of Ba(OAc)2 (1-2 mM). These separations include aldohexoses (i.e., galactose, glucose, and mannose), aminohexoses (i.e., glucosamine and galactosamine) and their N-acylated derivatives (i.e., N-acetylglucosamine and N-acetylgalactosamine) along with some isomeric disaccharides (i.e., lactose, lactulose and epilactose). The separation of closely related isomers of trehalose, alpha,alpha, alpha,beta, and beta,beta, is also presented. It is recommended to add Ba(OAc)2 to NaOH solutions several hours before using the alkaline eluent (i.e., 12-24 h) to ensure complete barium carbonate precipitation in the eluent reservoir. Adopting such a simple strategy can be especially useful for performing carbohydrate separations under isocratic conditions in which no regeneration and or re-equilibration of column between runs is required. Excellent repeatability of retention data throughout a three-day working session was observed, with relative standard deviations ranging from 2.0 to 3.7%, and from 0.5 to 2.0%, as day-to-day and within-day values, respectively. In addition, there was no need for postcolumn addition of strong bases to the eluent, and successful applications of the present approach confirmed its validity and practicability with detection limits of simple carbohydrates in the picomole range.

Removal of diclofenac potassium from wastewater using clay-micelle complex

The presence of an ionized carboxyl group in the widely used non-steroidal anti-inflammatory (NSAID) drug diclofenac potassium results in a high mobility of diclofenac and in its low sorption under conditions of slow sand filtration or subsoil passage. No diclofenac degradation was detected in pure water or sludge during one month. Tertiary treatments of wastewater indicated that the effective removal of diclofenac was by reverse osmosis, but the removal by activated carbon was less satisfactory. This study presents an efficient method for the removal of diclofenac from water by micelle–clay composites that are positively charged, have a large surface area and include large hydrophobic domains. Adsorption of diclofenac in dispersion by charcoal and a composite micelle (otadecyltrimethylammonium [ODTMA] and clay [montmorillonite]) was investigated. Analysis by the Langmuir isotherm revealed that charcoal had a somewhat larger number of adsorption sites than the composite, but the latter had a significantly larger binding affinity for diclofenac. Filtration experiments on a solution containing 300 ppm diclofenac demonstrated poor removal by activated carbon, in contrast to very efficient removal by micelle–clay filters. In the latter case the weight of removed diclofenac exceeded half that of ODTMA in the filter. Filtration of diclofenac solutions at concentrations of 8 and 80 ppb yielded almost complete removal at flow rates of 30 and 60 mL min−1. One kilogram of ODTMA in the micelle–clay filter has been estimated to remove more than 99% of diclofenac from a solution of 100 ppb during passage of more than 100 m3.

Collision-Induced Dissociation of the A + 2 Isotope Ion Facilitates Glucosinolates Structure Elucidation by Electrospray Ionization-Tandem Mass Spectrometry with a Linear Quadrupole Ion Trap

An approach is presented that can be of general applicability for structural elucidation of naturally occurring glucosinolates (GLSs) in crude plant extracts based on the fragmentation of isotopic A and A + 2 peaks. The most important fragmentation pathways were studied by tandem mass spectrometry (MS(n), n = 2, 3) using a linear quadrupole ion trap (LTQ) upon GLSs separation by optimized reversed-phase liquid chromatography (RPLC) and electrospray ionization (ESI) in negative ion mode. As the LTQ MS analyzer ensures high sensitivity and linearity, the fragmentation behavior under collision induced dissociation (CID) of the isotopic peaks A and A + 2 as precursor ions was carefully examined. All GLSs (R-C(7)H(11)O(9)NS(2)(-)) share a common structure with at least two sulfur atoms and significant isotopic abundance of (34)S. Thus, dissociation of the +2 Da isotopomeric ions results in several fragment ion doublets containing a combination of (32)S and (34)S. Accordingly, their relative abundances allow one to speed up the structural recognition of GLSs with great confidence, as it produces more structurally informative ions than conventional tandem MS performed on A ions. This approach has been validated on known GLSs bearing two, three, four, and six sulfur atoms by comparing expected and measured isotopic peak abundance ratios (I(A)/I(A)(+2)). Both group- and compound-specific fragments were observed; the predominant pathway of fragmentation of GLSs gives rise to species having the following m/z values, [M - SO(3) - H](-), [M - 196 - H](-), [M - 178 - H](-), and [M - 162 - H](-) after H rearrangement from the R- side chain. The present strategy was successfully applied to extracts of rocket salad leaves (Eruca sativa L.), which was sufficient for the chemical identification of a not already known 6-methylsulfonyl-3-oxohexyl-GLS, a long-chain-length aliphatic glucosinolate, which contains three sulfurs and exhibits a deprotonated molecular ion at m/z 494.1.

Photochemical behaviour of oxyfluorfen: a diphenyl-ether herbicide

Abstract The photochemical behaviour in different solvents of the herbicide oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (CAS RN 42874–03–3)] was studied. Photochemical reactions were carried out by using a high pressure mercury arc and a solar simulator. Kinetic parameters and quantum yields were determined. Identification of the photoproducts was performed by GC-MS and the main compounds were confirmed by [ 1 H] NMR. The photochemical reactions were also carried out in the presence of either a singlet or a triplet quencher, and in the presence of either a radical initiator or a radical inhibitor. Results indicate that the first excited singlet state can undergo both homolytic and heterolytic cleavage of the ethyl-oxygen bond in the side chain of oxyfluorfen. Moreover, the presence of reduction products in the reaction mixture is supposed to occur via a monoelectron transfer process with the formation of a transient exciplex during the reaction.