bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ammonium nitrate fertility levels influence flavour development in hydroponically grown ‘Granex 33’ onion
Authors: Coolong Timothy W , Randle William M 
Published: March 2003

AbstractHigh levels of nitrogen (N) fertility have been shown to influence bulb flavour characteristics in onion (Allium cepa L). To test the effects of lower levels of N fertility on onion bulb flavour, ‘Granex 33’ onions were grown hydroponically in a greenhouse with varying solution N levels. Eleven levels were tested by increasing the concentration of NH4NO3 in solutions from 20 to 140 mg l−1 N. Mature plants were harvested and evaluated for plant leaf and bulb fresh weights (FWs), bulb soluble solids content (SSC), bulb total pyruvic acid, bulb total sulphur (S), and bulb sulphate (SO42−). To determine the effect of N on the flavour biosynthetic pathway of onion, total and individual S‐alk(en)yl cysteine sulphoxides and related peptide intermediates were also tested. Leaf and bulb FWs responded quadratically to N concentration, as did total bulb S. Bulb SO42− and SSC, though significantly influenced by N concentration, did not respond with a meaningful trend. Bulb pyruvic acid increased linearly with N level increases, as did (+)‐S‐propyl‐L‐cysteine sulphoxide. Total precursors, (+)‐S‐methyl‐L‐cysteine sulphoxide, and trans‐(+)‐S‐1‐propenyl‐L‐cysteine sulphoxide responded quadratically to N levels. At lower N levels, trans‐(+)‐S‐1‐propenyl‐L‐cysteine sulphoxide content was highest relative to the other precursors. However, at elevated N levels, (+)‐S‐methyl‐L‐cysteine sulphoxide accumulated in the highest concentrations. Peptide intermediates 2‐carboxypropyl glutathione and γ‐glutamyl propenyl cysteine sulphoxide responded linearly and quadratically respectively to increasing N fertility levels. Nitrogen fertility levels can influence flavour intensity and quality and should be considered when growing onions for flavour attributes. Copyright © 2003 Society of Chemical Industry
Fibre‐optic method for estimation of bovine fat quality
Authors: Irie M , Oka A , Iwaki F 
Published: March 2003

AbstractSpectroscopy using remote surface, contact, insertion and transmission fibre‐optic probes and a sensor at wavelengths of 400 to 1100 nm was used for rapid estimation of the physio‐chemical characteristics of bovine fat. Surface reflectance of the adipose tissue was negatively correlated with the bovine fat colour score at many wavelengths and positively correlated with the contents of the polyunsaturated fatty acids at 400 to 650 nm (P < 0.05). Internal reflectance using an insertion probe at 445 to 1100 nm was positively correlated with melting point and negatively correlated with refractive index (P < 0.05). Internal reflectance using a contact probe tended to be related to saturated and monounsaturated fatty acid contents. Transmittance at almost all wavelengths was positively correlated with refractive index (P < 0.05). Internal reflectance of the intermuscular fat from 34 animals measured at a meat market was correlated (P < 0.01) with saturated fatty acid content (r = 0.72 at 650 nm) and with monounsaturated fatty acid content (r = −0.69 at 650 nm). These results indicated the possibility of using fibre‐optic measurements, requiring 1 s in bovine adipose tissue, to evaluate the quality of depot fat and that the various types of probe can be used to evaluate different physiochemical characteristics of fat. Copyright © 2003 Society of Chemical Industry
Evolution of available lysine and furosine contents in milk‐based infant formulas throughout the shelf‐life storage period
Authors: Ferrer Emilia , Alegría Amparo , Farré Rosaura , Abellán Pedro , Romero Fernando , Clemente Gonzalo 
Published: March 2003

AbstractThe evolution of the Maillard reaction (MR) by measuring the available lysine and furosine (FUR) contents in adapted and follow‐up powdered milk‐based infant formulas over the shelf‐life storage period, at 20 and 37 °C, was studied. Available lysine and FUR contents were determined by fluorimetry and high‐performance liquid chromatography respectively. Statistically significant differences were found between adapted and follow‐up infant formulas with respect to the available lysine and FUR contents. Available lysine contents decreased significantly throughout the storage time, and the contents at 37 °C were lower than at 20 °C. A statistically significant increase in FUR contents was observed during the storage period, with the contents being high at 37 °C than at 20 °C. A simple regression analysis between the available lysine and FUR contents during (a) the first year (b) the second year and (c) the two storage years was applied. The best correlations were obtained during the first year of storage. The results obtained show a clear MR evolution during the storage of infant formulas. Copyright © 2003 Society of Chemical Industry
Measurement of the parameters of the mass transfer kinetics in high performance liquid chromatography
Authors: Miyabe Kanji , Guiochon Georges 
Published: March 2003

AbstractFundamental studies of the mass transfer kinetics are as essential as those of the retention equilibrium for a detailed understanding of the characteristics and the mechanisms of chromatographic separations. The acquisition of a large amount of reliable experimental data and of meaningful results is necessary for any further progress of our knowledge of kinetics. The main goal of this review is to provide information on the methods used to perform accurate measurements and on the data analysis procedures used for deriving the kinetic parameters characterizing mass transfer in HPLC. First, the general characteristics of several methods of determination of some kinetic parameters are briefly reviewed. Secondly, we give detailed explanations of the experimental conditions of the pulse on a plateau method (i.e., elution chromatography on a plateau of finite concentration or pulse response method) and of the data analysis procedures based on moment analysis. Thirdly, we explain some important requirements for the acquisition of appropriate experimental data and discuss corrections to be applied when deriving several kinetic parameters. Fourthly, we discuss the accuracy of the kinetic parameters derived from the pulse on a plateau method and from moment analysis. Finally, some results concerning the mass transfer kinetics in RPLC systems are demonstrated as examples.
Characterization of HPLC packings
Authors: Neue Uwe D. , Van Tran Kim , Iraneta Pamela C. , Alden Bonnie A. 
Published: March 2003

AbstractSeveral chromatographic test procedures are in use for the characterization of commercially available packings. The results of the test procedure used in our laboratory are updated and further refined. Two well‐defined physico‐chemical properties of packings can be derived from this test procedure, the hydrophobicity of a packing and the silanophilic activity at pH 7. In addition, our method is unique in its ability to differentiate between classical packings and packings with incorporated polar groups. We can also distinguish CN packings or fluorinated packings. Our database now includes over 100 commercially available packings. The ability of the test to cleanly discriminate between different classes of packings has been strengthened. Limited comparisons with other published tests are now possible as well, and the results of these comparisons are discussed.
Selection of suitable stationary phases and optimum conditions for their application in the separation of basic compounds by reversed‐phase HPLC
Authors: McCalley David V. 
Published: March 2003

AbstractIn this review, some aspects of the separation of basic compounds by HPLC are discussed with especial reference to work carried out by the author. Procedures for column evaluation are explained, together with the effect of mobile phase modifier, pH, temperature, nature of buffer, and sample overloading on the chromatography of basic compounds. Some evaluations of new column types, such as embedded polar group phases, monoliths, and hybrid inorganic/organic phases are presented.
Evaluation of column characteristics in RPLC using linear solvation energy relationships (LSERs)
Authors: Szepesy László 
Published: March 2003

AbstractAn overview is given of our studies on the use of linear solvation energy relationships (LSERs) for evaluation and comparison of RP‐HPLC columns. From among the columns investigated, 19 columns of different types, viz. 12 narrow‐pore, 7 wide‐pore silicas containing various ligands (C18, C8, C4, CN) and obtained from 7 manufacturers, were compared and evaluated. Retention factors of 32 solutes of widely differing chemical properties were measured and evaluated to determine the effect of stationary phase properties on the retention of various types of solutes. When the same mobile phase is used with the different columns, the regression coefficients determined by multivariate regression characterize the various stationary phases. The columns investigated were evaluated on the basis of the relative importance of the various types of interactions reflecting the various surface properties of the stationary phases. Since the selectivity of separation is more important than is absolute selectivity, we have investigated and compared the various selectivity terms, hydrophobic, polar, and specific selectivity, displayed by the various columns, for the separation of different types of compounds. As the selectivity of separation depends also on the type and composition of the mobile phase, the effect of mobile phase on the various selectivity terms was evaluated.
NMR investigations of stationary phases
Authors: Albert Klaus 
Published: March 2003

AbstractAn overview of the application of solid‐state and suspended‐state NMR spectroscopy for the characterization of stationary phases is given. Solid‐state 29Si NMR spectroscopy reveals valuable information about the variety and quantity of the surface species formed in the modification reaction. Solid‐state 13C NMR spectroscopy gives an insight into the dynamic properties of the immobilized ligands and ligand organization. With the help of 1H and 13C suspended‐state NMR spectroscopy, investigations can be performed in the presence of a mobile phase. Thus, the structural and dynamic properties of the stationary phase under real‐life chromatographic conditions can be derived from the NMR investigations. These findings can be directly correlated with the resulting chromatographic separation behaviour.
Design and characterization of novel stationary phases based on retention behavior studies with various aromatic compounds
Authors: Saito Yoshihiro , Ohta Hatsuichi , Jinno Kiyokatsu 
Published: March 2003

AbstractCharacterization of stationary phases by retention behavior studies with aromatic compounds is reviewed, focusing mainly on the authors' approach. Various aromatic compounds, such as polycyclic aromatic hydrocarbons (PAHs) and fullerenes, of different molecular shape and size were employed as the sample probes. For the systematic analysis of retention behavior, some spectroscopic techniques and theoretical calculations, such as energy minimized calculation of the phase structure, have also been employed to confirm the results from these retention studies. During these investigations, microcolumn chromatography was employed in order to evaluate small amounts of experimentally synthesized bonded phases. The design of several novel stationary phases, based on the molecular shape recognition concept, is also briefly reviewed along with the applications.
Characterization of liquid chromatographic chiral separation on chiral crown ether stationary phases
Authors: Hyun Myung Ho 
Published: March 2003

AbstractCrown ether‐based chiral stationary phases (CSPs) have been known to be quite useful for the liquid chromatographic resolution of racemic compounds containing a primary amino group. Chiral separations on crown ether‐based CSPs are characterized by several factors. In this paper, the structural characteristics of five selected crown ether‐based CSPs, analyte characteristics and several factors characterizing chiral separations such as the mobile phase modifiers and the column temperature were reviewed. Among the various factors, the column temperature and the inorganic modifier in the mobile phase influence the chiral separations equally for the five selected crown ether‐based CSPs. In contrast, the effect of the organic and acidic modifier in the aqueous mobile phase on the chiral separations depends on the structural characteristics of CSPs.
The development of selective and biocompatible coatings for solid phase microextraction
Authors: Mullett Wayne M. , Pawliszyn Janusz 
Published: March 2003

AbstractThe development of solid phase microextraction (SPME) has seen huge growth since its conception as a new approach to sample preparation in the early 1990s. In comparison to existing technologies such as liquid‐liquid or solid phase extraction (LLE and SPE, respectively), the technique offers many advantages, including simplicity, speed, solventless extraction, and a convenient format. However, an important aspect in the future application and growth of SPME is the development of new extraction coatings. The objective of this review is to present an overview of the advances in coating development for solid phase microextraction (SPME). More specifically, this review will focus on the use of molecular recognition elements in SPME coatings to provide enhanced extraction selectivity and their applicability to the direct analysis of complex samples, such as biological fluids. The work will also include short overviews of emerging extraction phase technologies such as molecularly imprinted polymers (MIPs) and restricted access materials (RAM). The biocompatibility of RAMs has been combined with SPME and highlighted in several examples for more targeted and direct extraction possibilities in complex samples. The ability to perform direct and selective extraction of analytes from complex samples will extend SPME into the field of bioanalysis. Lastly, the future outlook for SPME and potential new applications for these fibers will be discussed.
Stationary phases for silver ion chromatography of lipids: Preparation and properties
Authors: Momchilova Svetlana , Nikolova‐Damyanova Boryana 
Published: March 2003

AbstractProcedures for the preparation of stationary phases for several silver ion chromatographic techniques have been surveyed. Thin‐layer chromatography (TLC), conventional (normal pressure) column chromatography, solid phase extraction (SPE), high‐performance liquid chromatography (HPLC), and supercritical fluid chromatography (SFC) in silver ion mode have been considered. The utilization of these stationary phases for the analysis of fatty acids and triacylglycerols has been demonstrated.
Prediction of gradient retention from the linear solvent strength (LSS) model, quantitative structure‐retention relationships (QSRR), and artificial neural networks (ANN)
Authors: Kaliszan Roman , Ba̧czek Tomasz , Buciński Adam , Buszewski Bogusław , Sztupecka Małgorzata 
Published: March 2003

AbstractThe linear solvent strength (LSS) model combined with quantitative structure‐retention relationships (QSRR) and artificial neural network (ANN) analysis has been shown to permit approximate prediction of the gradient high‐performance liquid chromatography (HPLC) retention time for any analyte on a once‐characterized column. The approach applies well to the reversed‐phase HPLC mode with a methanol‐water (buffer) eluent of linearly changing composition. Its suitability was tested for a representative series of structurally diverse analytes. In this approach the determination of retention times, t R, in two gradient runs for a predesigned model series of 15 analytes is first needed. Next, model QSRR equations describing t R in terms of analyte structure are derived to characterize the HPLC systems of interest. To quantitatively characterize the structure of the analytes the following three structural descriptors from molecular modeling are employed: total dipole moment; electron excess charge of the most negatively charged atom; and water‐accessible molecular surface area. Using these data a general QSRR equation is derived which is valid for a given column/eluent system. Next, having the structural descriptors for any analyte to be chromatographed in such a characterized HPLC system, one employs the previously derived general QSRR equation to calculate the analyte's retention time. The expected gradient retention time for any gradient conditions can be calculated by means of appropriate LSS equations. Independent of the standard QSRR calculation procedure based on multiple regression analysis (MRA), predictions of gradient retention times were performed by means of artificial neural networks (ANN). It has been found that the predictive power of ANN is similar to that of MRA. The combined LSS/QSRR approach has been demonstrated to provide approximate, yet otherwise unattainable, a priori predictions of gradient retention of analytes based solely on their chemical formulae. That way a rational chemometric basis for a systematic optimization of chromatographic separations has been elaborated as an alternative to the trial‐and‐error method normally applied at present.
A new standard reference material for column evaluation in reversed‐phase liquid chromatography
Authors: Sander Lane C. , Wise Stephen A. 
Published: March 2003

AbstractA new Standard Reference Material (SRM) for use in characterizing general aspects of liquid chromatographic column performance is described. SRM 870 Column Performance Test Mixture for Liquid Chromatography contains five components: uracil, toluene, ethylbenzene, quinizarin, and amitriptyline, and is intended to provide indications of column void volume, hydrophobicity, methylene selectivity, activity toward organic bases, and activity toward metal chelators. The test is performed under neutral, buffered conditions. The measurement of retention and peak asymmetry factors for the components facilitates column classification. It is anticipated that this material will be useful (1) in column selection during method development, (2) as a control material to monitor column performance over time, and (3) in quality control in column manufacturing.
Chromatographic classification and comparison of commercially available perfluorinated stationary phases for reversed‐phase liquid chromatography using Principal Component Analysis
Authors: Euerby Melvin R. , McKeown Alan P. , Petersson Patrik 
Published: March 2003

AbstractA range of ten perfluorophenyl and perfluoroalkyl stationary phases has been evaluated using standard chromatographic tests and probes. Principal Component Analysis of the data has indicated that the phases can be divided into distinct groupings. Extending the dataset to include standard alkyl and phenyl phases provided further data interpretation to support the orthogonal selectivity claims made for perfluorinated phases. The analysis of a range of basic analytes showed an unusual extended retention of hydrophilic basic analytes with perfluorophases. Furthermore, a non‐linear relationship between the amount of organic modifier and the logarithm of the retention factor was observed, for the hydrophilic bases, which could not be modelled with LC prediction softwares. This was in sharp contrast to the alkyl and phenyl phases examined. Basic analyte retention on perfluoroalkyl phases could be modelled adequately for the lipophilic bases. Exploration of the retention mechanism of these perfluoro phases indicated that silanol interactions were important in retention and selectivity. Using a rapid, isocratic, high organic modifier methodology, it was possible to analyse a mixture containing a lipophilic steroid, hydrophilic base and an internal standard in < 4 minutes with a perfluorophenyl phase. This had previously only been achievable with an alkyl phase under gradient elution conditions.
Study on conical columns for semi‐preparative liquid chromatography
Authors: Jiping Ma , Yafeng Guan , Lingxin Chen 
Published: March 2003

AbstractThe dynamic flow profiles and column efficiencies in conically shaped semi‐preparative liquid chromatographic columns (inlet ID larger than outlet ID) with two different conical angles (7° and 15°) were studied. The dynamic flow profiles were studied by an on‐column visualization method. Conical columns were compared with cylindrical column of the same length and internal volume. The results showed that the flow profile of a sample band in the conical column of 7° (50 mm×17 mm → 11 mm ID) was parabolic in shape. The sample band migrated slower in the wall region than in the central region, as in the cylindrical column (50 mm×14 mm ID). However, the sample band in the conical column of 15° (50 mm×20 mm → 7 mm ID) migrated slower in the central region than in the wall region, resulting in a reverse parabolic flow profile, in contrast to that in cylindrical column. This indicated that a flat flow profile might be realized in a conical column with a conical angle between 7° and 15°. The conical column of 15° had the highest column efficiency among the three columns under the same conditions. Compared with the cylindrical column packed with identical packing material, the conical column of 15° had 22%–45% higher column efficiency and 11%–27% higher peak height.
Evaluation of HPLC columns: A study on surface homogeneity of chemically bonded stationary phases
Authors: Buszewski Bogusław , Krupczyńska Katarzyna , Gadzała‐Kopciuch Renata M. , Rychlicki Gerhard , Kaliszan Roman 
Published: March 2003

AbstractThe aim of the current work is to study the heterogeneity of the adsorbent surface on the basis of physicochemical investigations and chromatographic tests. A series of packing materials with octadecyl chains chemically bonded to a silica matrix were prepared for this purpose. The surface and structural properties of bare silica and silica‐based octadecyl phases were characterized by porosimetry, elemental analysis, 29Si CP/MAS NMR, etc. The most advanced characterization methods based on adsorption microcalorimetry (heat of wetting) measurements were employed to obtain information about the heterogeneity and topography of unmodified and modified silica gel. For the chromatographic study, these phases were evaluated on the basis of the retention data under non‐aqueous conditions. A test series of solutes with various chemical properties, such as pK a values, was used. It was found that heterogeneity of the packing surface results in low HPLC resolution. Use of a non‐aqueous mobile phase (n‐hexane) reduces analytical interference by eliminating hydrophobic interactions between alkyl ligands and the analyte.
Methacrylate monoliths prepared from various hydrophobic and hydrophilic monomers – Structural and chromatographic characteristics
Authors: Merhar Mojca , Podgornik Aleš , Barut Miloš , Žigon Majda , Štrancar Aleš 
Published: March 2003

AbstractMethacrylate‐based monoliths are formed during radical copolymerization as a consequence of the precipitation of polymeric chains from the reaction mixture, which consists of monomers, initiator, and the porogenic solvents. The effect of various methacrylate monomers on the porous structure of the monolith was investigated. Although the chemical structure of the monomers significantly affects the size of the pores and the porosity, the mechanism of pore formation in the case of the precipitation during polymerization is preserved. The porous structure was further correlated with the specific surface area, pressure drop, and dynamic binding capacity of the monoliths studied.