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Detecteurs optiques, a barette de diodes, laser, electrochimiques, du type CG, a induction de plasma

The advantages of short microbore columns packed with a sorbent having a particle diameter of 3µm, such as the speed of analysis, the high solute concentration in the effluent and the detectability of small quantities are experimentally verified. The broadening in the valve is eliminated by the peak compression technique reached by adding a ion-pairing agent into the sample. The examples of catecholamines show the dependence of the height equivalent to a theoretical plate on the velocity of the mobile phase. The optimum is h=3 for a column 30mm long, i.d. 0.7mm, particle diameter 3µm. The minimal detectable quantity with a two-electrode amperometric detector with a gold electrode is from 30 to 40fmol for catecholamines.

Utilisation des techniques de spectrometrie IR a transformee de Fourier, de la chromatographie en couche mince avec de l'alumine et de la chromatographie HPLC en phase inverse afin d'identifier des composes de melanges complexes

The chromatographic performance of deuterated solvents, heavy water and deuteriobenzene, has been investigated in reversed phase and normal phase micro-HPLC. The performance of heavy water in separation was comparable or superior to that of light water in reversed phase mode. A slight improvement was also observed in catecholamines separation with heavy water. The performance of deuteriobenzene was observed as complicated in metal complexes separation, but a little difference was present. From those results, the combinations of micro HPLC and IR via flow-cell technique, proton-NMR, and ICP could be accomplished free from absorption or signals from mobile phase solvents.

A simple scheme was developed by utilization of a micro-HPLC technique in order to monitor synthetic reactions in-situ. The application of this system for the organic reaction of bromination of toluene was successfully presented.

High-performance micro packed fused-silica and open-tubular glass capillary columns were prepared and applied to separations of complex mixtures. Solvent-gradient elution proved quite useful for the separation of solutes with wide polarity. Instruments and some applications are described.

The capcity factors determined by reversed-phase micro high performance liquid chromatography (micro-HPLC) can be used as one of the descriptors in Quantitative-Structure-Activity-Relationships (QSAR) studies. The present method gives a more simple and convenient way to study relationships between physicochemical properties and biological activities of some drugs.

A miniaturized continuous gradient elution system with variable gradient profile was designed. A retention time reproducibility below 1% was achieved. The system was applied to the separation of phenolic compounds with a wide range of polarities.

Phenol-formaldehyde resins of the Novolak and Resol type were chromatographed on a reverse-phase micro-column packed with octadecylsilane on silica gel. A good separation of most components was achieved by the use of gradient elution with methanol-water; the contents of methanol in the mobile phase increased continually from 10 to 90%. The gradient was generated in a simple tubular mixer with an internal volume of 1.5 ml. Samples were applied to the column in a non-eluting solvent, using a six-port injection value with a 10 μl sample loop. The method, which shows a good reproducibility, is suitable for the characterization of phenol-formaldehyde resins. Phenol-Formaldehyd-Harze vom Novolak- und Resol-Typ wurden durch Chromatographie an einer mit Octadecylsilan auf Kieselgel bepackten Umkehrphasen-Mikro-Saule getrennt. Eine gute Auftrennung der meisten Komponenten wurde durch die Verwenndung der Gradientelution mit Methanol und Wasser erzielt. Der Gradient wurde in einer Rohr-Mischkammer (Volumen 1,5 ml) erzeugt; der Anteil von Methanol in der mobilen Phase wurde im Verlauf der Analyse von 10 auf 90% kontinuierlich gesteigert. Die Probenaufgabe erfolgte mit Hilfe eines Dosierventils und einer Probenschleife (Volumen 10 μl). Das Verfahren ergab reproduzierbare Ergebnisse; es erwies sich als gut geeignet zur Charakterisierung von Phenol-Formaldehyd-Harzen.

The combination technique of micro high performance liquid chromatography and inductively coupled plasma atomic emission spectrometry is demonstrated in the separation of organometallic compounds. Problems relating to the interfacing between micro HPLC and ICP would be elininated uti1izing the simple interfacing technique.

A micro high-performance liquid chromatographic (micro-HPLC) method was developed for the determination of purpurea glycoside A, purpurea glycoside B, and glucogitaloxin in Digitalis purpurea leaves. The extract of dry leaf powder was applied to a Sep-Pak silica cartridge followed by preparative thin-layer chromatography prior to micro-HPLC analysis. The analysis was performed on an ODS micro column, using acetonitrile-methanol-water (21:20:45) and ultraviolet detection (220 nm). The amounts of purpurea glycoside A, purpurea glycoside B, and glucogitaloxin per 100 mg of dry leaf powder were estimated to be 52.6, 50.7, and 108.6 μg, respectively.

Application de la methode du titre a l'analyse des hydrocarbures paraffiniques et aromatiques d'une fraction essence

The interface for direct coupling of micro HPLC with FAB mass spectrometry has been evaluated as a simple sample introduction system using unstable and/or non-volatile compounds having higher molecular weight. The good reproducibility of chromatograms, little fluctuation and small tailing in chromatographic peak profiles, and the excellent quality of mass spectral patterns were obtained. High-molecular-weight compounds such as parathyroid hormone and insulin chain B could be introduced and ionized stably with high sensitivity.

The exclusion properties of ten commercially available silica gels have been determined and their relative merits for use as stationary phases in exclusion chromatography discussed. Examples are given of the use of three selected silica gels in the separation of synthetic mixtures of high-molecular-weight standards. The effect of the exclusion properties of silica gel on retention data is considered and a modified retention volume equation that takes into account these exclusion properties is given. The validity of the equation is tested against retention data determined for three different solutes chromatographed on three silica gels of widely different porosities. The use of silica gel as an exclusion medium in conjunction with a column having 250,000 theoretical plates is also demonstrated.

The chromatographic potential of very short fused-silica column (30 mm length) packed with 3-μm particles has been investigated. The results indicate that this kind of micro-column has high applicability for a rapid identification of several samples. This technique also meets the recent demands in HPLC, as low solvent consumption and faster analysis time.

The application of micro HPLC to the determination of amygdalin in Semen pruni armeniacae and Semen pruni persicae is described. Amygdalin is separated at ambient temperature on a reversed phase column of U-Finepak SIL C18(150 x 0.5 mm) with methanol + water (25:75 v/v) as the mobile phase at a flow rate of 10 microL/min. The results are calculated by the internal standard method. The linear range is 1-7 micrograms. The CV and recovery of pure amygdalin are 1.47% (n = 10) and 98.13%, respectively. The results of analysis are lower than those obtained by TLC, but microHPLC is much simpler, faster, and more sensitive and reproducible than TLC.

Utilization of micro-HPLC is described for the direct measurement of the partition coefficients needed in studying the quantitative structure — activity relationships (QSAR). The method involves analyzing the solutes in acetonitrile — water as the mobile phase on commercially available reversed-phase stationary phases.

Publisher Summary This chapter discusses the miniaturized voltammetric detectors. Micro high-performance liquid chromatography (micro HPLC) using packed columns of I.D. less than 1 mm and packed or open tubular capillary chromatography are attractive in that the consumption of the mobile phase and sample is much less than that in conventional HPLC. These extremely slow flow rates require small volume detectors and these have been designed for spectrophotometric detection by UV and fluorescence methods. The usefulness of electrochemical detectors has already been recognized. Numerous voltammetric detectors have been described for HPLC. These can be broadly divided into coulometric detectors that use a large surface area working electrode, and amperometric detectors that use a small surface area working electrode.

Publisher Summary This chapter discusses the combination of micro-HPLC and IR spectroscopy. High-performance liquid chromatography (HPLC) has become an extremely powerful technique for separating mixtures into their constituents , with the recent developments in the packing materials and pumps. HPLC permits separations of a wide variety of mixtures containing non-volatile or temperature-sensitive compounds which cannot be separated readily by gas chromatography (GC). However, no universal equivalent in HPLC to thermal conductivity or flame ionization detection in GC is available, because various mobile phases are used and the physical properties of both the mobile phase and the sample components are often quite similar. Although there are two detection methods based on UV absorption and refractive index, which are the most frequently used, they provide little structural information on the separated species. Infrared spectrometry ( I R ) is undoubtedly one of the most useful tools providing qualitative information.

The importance of dispersion in High Performance Liquid Chromatography (HPLC) is emphasised. The state of the art of Micro HPLC techniques such as high speed HPLC and narrow bore HPLC are reviewed.

Various types of open-tubular capillary columns are prepared and employed as separation tools in liquid chromatography(LC). Preparation procedures and the apparatus for open-tubular capillary LC are described and the performance of capillary columns is discussed.

Publisher Summary This chapter discusses the instrumentation and applications of micro-liquid chromatography/mass spectrometry. Micro high performance liquid chromatography (micro HPLC) is finally enjoying increased consideration and applications. Several manufacturers are now marketing either modified conventional HPLC equipment, or entirely new hardware designed to deliver micro LC flow rates ranging usually from 10-100 micro liters per minute. There are a variety of reported benefits or reasons for utilizing micro LC rather than conventional HPLC, but usually the most justifiable reasons for "bothering" with micro LC include HPLC solvent savings and on-line high performance liquid chromatography/mass spectrometry (LC/MS). This chapter reviews on micro LC/MS with emphasis placed upon practical applications which demonstrate the sensitivity gains available when total introduction of micro LC effluent is provided to the mass spectrometer.

The possibility of high-speed micro-HPLC has been investigated using a short micro-column (35 mm × 0.5 mm i.d.) packed with 3 μm ODS particle. The results indicate that this approach has considerable potential for good separations with short analysis time. A typical example shows only three minutes is required with a plate count of 3,800 to separate seven PAHs.

The separation of polycyclic aromatic hydrocarbons (PAH) on various reversed-phase columns (phenyl, ethyl, octyl and octadecyl) have been compared. The correlations between the logarithm of capacity factor (log k′) and several descriptors, which show the molecular size, shape and physical property of a solute, were determined. The results indicated the high possibility to predict the retention of PAH in reversed-phase high performance liquid chromatography.