J.A. Pérez-Bustamante

Analytical applications of some flotation techniques-a review.

A review is given of the principles and more recent applications of foam flotation.

Objective functions in experimental and simulated chromatographic optimization : Comparative study and alternative proposal

Abstract The rǒle of the objective function in chromatographic optimization and method development is emphasized by a critical study of several functions proposed in the literature. Different properties are discussed for characterizing an ideal (if this exists) chromatographic objective function to be used in experimental or simulated off-line chromatographic optimization. In this context a new information theory-based criterion is proposed.

Simultaneous separation of copper, cadmium and cobalt from sea-water by co-flotation with octadecylamine and ferric hydroxide as collectors.

A method is proposed for the simultaneous quantitative separation of traces ofCu(II), Cd(II) and Co(II) from sea-water samples by means of the co-flotation (adsorbing colloid flotation) technique with ferric hydroxide as co-precipitant and octadecylamine as collector. The experimental parameters have been studied and optimized. The drawbacks arising from the low solubility of octadecylamine and the corresponding sublates in water have been avoided by use of a 6M hydrochloric acid-MIBK-ethanol (1:2:2 v v ) mixture. The results obtained by means of the proposed method have been compared with those given by the usual ammonium pyrrolidine dithiocarbamate/MIBK extraction method.

Ligands with the “ONNN” Group as Chelating and Preconcentrating Substances of Heavy Metal Ions: Aroylhydrazone Derivatives from Di-2-Pyridyl Ketone

The synthesis of the electronic and infrared spectra of di-2-pyridyl ketone salicyloylhydrazone (DPKSH) and di-2-pyridyl ketone benzoylhy-drazone (DPKBH) is reported. Ultraviolet absorption spectra have been applied for determining the dissociation constants: DPKSH, pK1 = 3.5 and pK2 = 6.85; DPKBH, pK1 = 2.75 and pK2 = 10.6. These pK a values are interpreted as a function of the ortho-position of the OH group. Chelating properties of both tridentate ligands have been investigated. DPKSH forms a larger number of metal chelates in acidic media than does DPKBH. Also, it is concluded that DPKSH is a more suitable compound than DPKBH to preconcentrate and to determine heavy metal ion traces as it is inferred from the data obtained by flame AAS.

Automated on-line-solid-phase extraction—high-performance liquid chromatography-diode array detection of phenolic compounds in sherry wine

A new analytical method has been developed for sample preconcentration and analysis of phenolic compounds in sherry wine using on-line solid-phase extraction(SPE)-HPLC-diode array detection. The samples of wine were injected and adsorbed onto polystyrene divinylbenzene cartridges; a robotic semiflexible system was used to automate the SPE stage. Chromatographic separation was carried out in a Symmetry C18 steel cartridge, with a two-step elution gradient. Peaks were identified by comparing their UV spectra with the library of spectra compiled by the authors.

Selection of column and gradient for the separation of polyphenols in sherry wine by high-performance liquid chromatography incorporating internal standards

Abstract A chromatographic column was selected, out of five possibilities tested, which offered sufficient efficiency to separate 21 out of 22 polyphenolic compounds, and the optimum elution gradient. Applied to samples of “fino” sherry wine, a satisfactory resolution of peaks was achieved, which allowed for the inclusion of an internal standard. The chromatographic behaviour of three polyphenolic standard substances was studied using the column and gradient selected, with a view to using them as internal standards for controlling the reliability of the analysis. It was concluded that all three can be used for this task, although 2,5-dihydroxybenzaldehyde is the most suitable in terms of ease of detection at 340 nm; however, the possibility of using the other two phenolic acids, β-resorcylic and 2,6-dimethyoxybenzoic acid, is not discarded as they could conveniently be made use of depending on the chromatographic profile of the sample to be analyzed.

Analysis of polyphenolic compounds of different vinegar samples

ZusammenfassungEine Methode für die Bestimmung von niedrig-molekularen polyphenolischen Verbindungen in Essig-Proben wurde optimiert und an verschiedenen Essig-Typen angewandt. Ethylacetat wurde als Extraktionsmittel benutzt in Verbindung mit einem kontinuierlichen Rotationsextraktor. Das ermöglicht die gleichzeitige Extraktion von zwölf Proben. Die entsprechenden Extrakte wurden einer HPLC-Trennung unterzogen, wobei eine C18-Umkehrphasen-Säule unter Gradientelution angewandt wurde. Die Identifizierung von polyphenolischen Verbindungen mittels eines Photodiodendetektors wurde durchgeführt. Wichtige Unterschiede in der Zusammensetzung der Phenole in den untersuchten Proben konnten nachgewiesen werden.AbstractA method for the determination of low-molecular-mass polyphenolic compounds in vinegars has been optimized and applied to different samples. Ethyl acetate has been used for the extraction of the polyphenolic compounds in a continuous rotatory system, furnished with a special device that allows for the simultaneous extraction of twelve samples. The extracts obtained were submitted to HPLC separation using a C18 reversed-phase column and gradient elution. The identification of polyphenolic compounds was carried out using a photodiode detector. Important differences were found in the phenolic content of the different samples. Best extraction yields were obtained when using 80 ml ethyl acetate and 300 steps (2 h 5 min) at a velocity of 0.8 rpm. The reproducibility of the method may be considered quite good. The method has been successfully applied to the analysis of real samples of very different kinds of vinegar. There are very interesting differences between the low-molecular-mass phenolic fraction of the vinegar analysed. Some interesting low-molecular-mass phenolic compounds have been identified. Their concentration, as well as the concentrations of other so far non-identified substances, depend upon the type of sample. The individual investigation of these phenolic compounds may furnish hints enabling the origin and type of vinegar to be traced. The elaboration type used in connection with the starting wine can be ascertained and differentiated, together with the ageing system used, through inference from the analytical data obtained from different vinegars.

The preopt package for pre-optimization of gradient elutions in high-performance liquid chromatography

Abstract A theoretical model is described for quick pre-optimization of binary multistep gradient elutions in liquid chromatography. This model utilizes experimental retention-time data under isocratic elution conditions for different proportions of organic modifier in the mobile phase, and simulates the position of the peaks in the chromatogram by calculation of the average velocity of the peaks through the column. Optimization is done for multistep gradients by means of the simplex algorithm. The results must then be confirmed experimentally. Results are given demonstrating the power and validity of the model in the resolution of complex mixtures. The whole process done on a micro-computer with the PREOPT package usually takes about 30 min, without requiring user participation or chromatographic instrumentation.

HPLC separation of benzoic and hydroxycinnamic acids in wines

SummaryAn HPLC gradient elution procedure which allows the separation of the great majority of phenolic acids (derived from benzoic and cinnamic acids) in wine is proposed. The method has been applied to the separation and identification of the phenolic acids of “Fino” sherry wine, as well as to establishing the generation of such substances during the browning processes typically undergone by such wines, as a function of the winemaking conditions.

Analysis of low molecular mass phenolic compounds, furfural and 5-hydroxymethylfurfural in Brandy de Jerez by high-performance liquid chromatography-diode array detection with direct injection☆

Abstract The polyphenolic composition of aged distillates originates principally from the ageing process in oak casks. It is accounted for by a narrow range of species. The relative simplicity of this wine industry product permits the analysis by HPLC with direct injection. The repeatability of the method has proved very high, in respect of both retention times and peak areas. The initial optimization of the elution gradient was completed by means of a solution comprising a mixture of standards and was definitely improved using real samples. A C18 column, 25 cm × 4 mm I.D., was used, with a particle size of 5 μm. Spectrophotometric detection, covering the UV-Vis range of 240–390 nm, was performed using a photodiode array detector.