Synthesis and characterization of polymer-coated mixed-functional stationary phases with several different hydrophobic groups for direct analysis of biological samples by liquid chromatography

Simultaneous quantitation of sphingoid bases and their phosphates in biological samples by liquid chromatography/electrospray ionization tandem mass spectrometry

We developed a liquid chromatography/electrospray ionization tandem mass spectrometry method for the simultaneous quantitative determination of C18 sphingosine (Sph), C18 dihydrosphingosine (dhSph), C18 phytosphingosine (pSph), C18 sphingosine-1-phosphate (S1P), C18 dihydrosphingosine-1-phosphate (dhS1P), and C18 phytosphingosine-1-phosphate (pS1P). Samples were prepared by simple methanol deproteinization and analyzed in selected reaction monitoring modes. No peak tailing was observed on the chromatograms using a Capcell Pak ACR column (1.5 mm i.d. × 250 mm, 3 μm, Shiseido). The calibration curves of the sphingoids showed good linearity (r > 0.996) over the range of 0.050-5.00 pmol per injection. The accuracy and precision of this method were demonstrated using four representative biological samples (serum, brain, liver, and spleen) from mice that contained known amounts of the sphingoids. Samples of mice tissue such as plasma, brain, eye, testis, liver, kidney, lung, spleen, lymph node, and thymus were examined for their Sph, dhSph, pSph, S1P, dhS1P, and pS1P composition. The results confirmed the usefulness of this method for the physiological and pathological analysis of the composition of important sphingoids.

A protein recycling system for nuclear magnetic resonance-based screening of drug candidates

A sample-treating system for nuclear magnetic resonance (NMR)-based interaction screening between drug candidates (small molecules) and a protein of interest was developed by applying high-performance liquid chromatography (HPLC) technology. The system prepares a test solution by mixing a (15)N-labeled protein solution and a solution of each candidate compound, loads it to a flow cell-type NMR probe, and recycles the protein after the data acquisition. The system was designed to behave differently according to the information obtained in NMR measurements. In a test operation with a 100-compound library, the system could single out known interacting substances properly. Recovery values of the protein and one representative compound were 75 and 71%, respectively, and the recovered protein was found intact as intended.

Development of restricted-access media supports and their application to the direct analysis of biological fluid samples via high-performance liquid chromatography

A quick overview of published methods for analyzing compounds in complex biological samples reveals that the most difficult step is the clean-up or extraction of a required compound from the matrix. The strategy required to analyze exogenous compounds in biological fluids depends greatly upon the nature of the compound and upon the biomatrix. Coupled-column separation using restricted-access media as the first dimension in order to exclude macromolecules and retain micromolecules has been successfully used for a number of biological fluids. This paper presents the history of the development of restricted-access media supports and of their application to the direct injection of biological fluid samples in high-performance liquid chromatography.

Synthesis and characterization of stable polymer-coated C8 stationary phase with high durability under extreme pH conditions for high-performance liquid chromatography

A highly chemically stable polymer-coated silica-based C8 stationary phase was developed by combining modification with octyl groups and a polymer coating technology. The stationary phase was prepared by the following procedure: (1) introduction of octyl groups to the silica surface; (2) coating the C8 silica with a silicone polymer. 29Si solid-state NMR spectra indicated that a silicone polymer reacted not only with residual silanol groups on the silica surface, but with those generated from silanes used for the introduction of octyl groups. Column durability was evaluated with an acidic mobile phase (60 degrees C, pH 1) and a basic mobile phase (50 degrees C, pH 10) in accelerated damaging conditions. The C8 phase showed a high durability under both conditions.

Evaluation of an ODS Column Modified with Zwitterionic/Nonionic Mixed Surfactants and Its Application to Direct Injection Determination of Inorganic Anions

An octadecylsilica (ODS) column modified with zwitterionic/nonionic mixed surfactants was evaluated for the direct injection determination of inorganic anions in biological fluids by ion chromatography. A zwitterionic surfactant (sulfobetaine-type) and a nonionic surfactant (polyoxyethylene-type) were used for a stationary-phase modification. When aqueous electrolyte solutions with concentrations of sub-mM to several mM were used as a mobile phase, the zwitterionic surfactant coated on the ODS surface exhibited unique separation selectivity for ionic species, while the nonionic surfactant coated on the ODS might have formed a hydrophilic network over the ODS surface and restricted matrix proteins from adsorbing on the stationary phase. Consequently, the mixed surfactant-modified column system allowed an efficient ion chromatographic separation of inorganic anions as well as a size-exclusive removal of column-fouling proteins. This separation system was applied to the direct injection determination of UV-absorbing anions in human saliva. The detection limits for nitrite, nitrate, iodide and thiocyanate were 3.1, 2.7, 4.5 and 25 microM, respectively, with UV detection at 210 nm (injection volume; 20 microl), and their relative standard deviations for 5 replicate measurements of saliva samples spiked with 100 microM each of those anions were 1.4, 0.9, 2.2 and 5.5%, respectively.

New synthetic ways for the preparation of high-performance liquid chromatography supports

The latest developments and in particular important synthetic aspects for the preparation of modern HPLC supports are reviewed. In this context, the chemistry of inorganic supports based on silica, zirconia, titania or aluminum oxide as well as of organic supports based on poly(styrene-divinylbenzene), acrylates, methacrylates and other, more specialized polymers is covered. Special consideration is given to modern approaches such as sol-gel technology, molecular imprinting, perfusion chromatography, the preparation of monolithic separation media as well as to organic HPLC supports prepared by new polymer technologies such as ring-opening metathesis polymerization. Synthetic particularities relevant for the corresponding applications are outlined.

Direct determination of bisphenol A and nonylphenol in river water by column-switching semi-microcolumn liquid chromatography/electrospray mass spectrometry

A rapid and sensitive analytical method based on column-switching semi-microcolumn high-performance liquid chromatography (HPLC) with electrospray mass spectrometry was developed for determining trace levels of bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and nonylphenol (4-nonylphenol) in river water. An aliquot of sample solution was directly injected into the precolumn packed with Capcellpak MF-Ph for sample cleanup and enrichment. The compounds of interest were then transferred to a C-18 analytical column for main separation through a change in flow path by a programmed switching valve. Bisphenol A, nonylphenol, and interfering substances were satisfactorily separated with a simple gradient elution complete within 35 min. Detection of their deprotonated molecules was conducted in negative ion mode. A reduced flow rate (100 &mgr;L/min) optimized for the narrow bore column was found advantageous in obtaining a high degree of sensitivity during electrospray detection. The influence of carrier additives on sensitivity was also examined. This method produced detection limits of 0.5 ng/mL for bisphenol A and 10 ng/mL for nonylphenol (signal-to-noise ratio 3). Calibration curves were observed in the range of 2.5-50 ng/mL (r(2) = 0.999) for bisphenol A and 50-500 ng/mL (r(2) = 0.998) for nonylphenol. Recoveries of the compounds from spiked distilled water and river water were 99.7-138.5% with a relative standard deviation (RSD) ranging from 2.2-9.7%. Copyright 1999 John Wiley & Sons, Ltd.

New packing materials for protein chromatography

This review describes new packing materials designed for protein chromatography, covering advances in base supports and stationary phases. Base supports are classified according to their chemical composition. Since most separation media are bead shaped, typical procedures used for their preparation are also presented. In order to provide matrices combining improved chemical stability and chromatographic performances, composite materials continue to be developed, including bonded stationary phases, pore composites and mixed carriers. The different approaches to their preparation are described and characteristics that play a major role in the chromatographic process are discussed. Recently introduced materials and some of their applications under non-denaturing conditions in the different chromatographic modes are also presented.