1,720,973 research outputs found
Applicazione della Elettro-Ultrafiltrazione (EUF) nella diagnosi di fertilità dei suoli. II: riproducibilità di alcune determinazioni di potassio
No full textEUF-K desorption from Alfisol and volcanic Inceptisol as influenced by temperature and potassium addition
No full textCinetica di desorbimento del fosforo determinata in EUF su suoli tipici dell'Italia Meridionale
No full textEvaluation of dicarboximide residues in cold-stored grapes exposed to field and post-harvest treatments
No full textOptimizing Separation Conditions for Riboflavin, Flavin Mononucleotide and Flavin Adenine Dinucleotide in Capillary Zone Electrophoresis with Laser-Induced Fluorescence Detection
No full textA 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 (15-30degreesC) and injection time. Optimal resolution and detection were obtained with a pH 9.8, 30 mM aqueous phosphate buffer at 15degreesC 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(cm)greater than or equal to515 nm. Riboflavin could be determined in the concentration ranges 0.5-350 mug/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. (C) 2002 Published by Elsevier Science B.V
Primi accertamenti sulla frazioni di potassio in alcuni suoli della Italia Meridionale determinate secondo il metodo della Elettro-Ultrafiltrazione (EUF)
No full textCollision-Induced Dissociation of the A+2 Isotope Ion Facilitates Glucosinolates Structure Elucidation by ESI-Tandem Mass Spectrometry with a Linear Quadrupole Ion Trap
No full textAn 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
Modificazioni indotte da differenti pratiche agronomiche su alcuni parametri biochimici e microbiologici del suolo
No full textInfluenza di differenti lavorazioni ed avvicendamenti colturali sulla biomassa microbica e sul biochimismo del suolo
No full textKinetics of phosphorus release from Italian alfisol and volcanic inceptisol as influenced by phpsphate additions to soil and by temperature
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