Particle Size Of Stationary Phase Research Articles

Separating and filtering compound mixtures using a magnetic field

Currently there is research in using magnetic fields to produce reactions and altering properties of compounds. This research has given promising results such as using a magnetic field to improve hydrocarbon fuel combustion. Results have shown better fuel efficiency and exhaust emissions reduction by using a magnetic field of varying strengths. This research has shown that other compound properties such as viscosity, surface tension, boiling point, can be altered with a sufficiently strength magnetic field. It has even been shown that IR and UV spectra can be enhanced by a magnetic field. Here the discussion will focus on showing potential magnetic field use in the separation sciences - stating the current research and developments of using magnetic filtering in separating compounds. Separation science deals with using mobile and stationary phases to separate compound mixtures in HPLC and GC. Factors such as flow rate, temperature, stationary phase particle size, and mobile phase solvent play key roles in separation. Other methods such as electrophoresis and dialysis use techniques similar to HPLC and GC. Here will be shown the potential of how a magnetic field can used separating compounds; organic and bioorganic including proteins, viruses, and even bacteria. First briefly discussing magnetic/electric fields and on organic and bioorganic compounds emphasizing on nucleophilic/electrophilic compounds, proteins, nucleotides, and microorganisms. Continued with examples of the research on using magnetic fields to filter and/or separate compounds and solution mixtures of aqueous/nonaqueous nature emphasizing on the research in oil spill clean-ups, blood dialysis and space applications.From what was presented, it will be shown how this research can be applied to four main areas. In electrophoresis, it will show the advantages of a magnetic field over the electric one. The removing of deadly diseases such as the coronavirus and wastes from blood using magnetic dialysis. The use in sample preparation methods. For HPLC/GC separations focus will be on magnetic separation enhancement and advantages of a proposed magnetic stationary phases over the current ones.The potential of magnetic field use in the separation sciences is great. Based on previous research such as improving fuel combustion has shown practical potential in other areas such mixture separations. By discussing the principals involved in this shows how it is achieved. The potential feasibility in improving electrophoresis, dialysis, and HPLC/GC separations can help reduce costs and preparation time.

Thin-layer chromatography of some derivatives of 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazoles in magnetic field

In this study, an investigation on the effect of the magnetic field on interphase phenomena influencing chromatographic separation was performed using thin-layer chromatography method. The presence of perpendicular to plane of the plate and the direction of chromatogram development magnetic field influences the interaction among all components of the chromatographic system. In consequence, the retention and efficiency of the investigated compounds in the given system should be altered. In this article, the effect of the field presence regarding retention mechanism, distance of development, and particle size of stationary phase for chosen derivatives of 2-(2,4-dihydroxyphenyl))-1,3,4-thiadiazoles is being investigated. The alteration of each abovementioned parameter affects the retention change caused by the field. It was also observed that the retention changes depend also on the structure of the studied compound, which may be a useful information for investigations on properties of newly synthesized comp...

Ultra-Performance Liquid Chromatographic Separation and Mass Spectrometric Quantitation of Physiologic Cobalamins

The current analytical high-performance liquid chromatography (HPLC) methods by which the various forms of cobalamin can be separated and quantified are limited to tedious chromatographic gradients with run times of 20―30 min and limits of detection (LOD) of 2 nM (2.7 ng/mL). This LOD is far above the physiological range of 148―443 pM (200―600 pg/mL) that is the normal total cobalamin level in human plasma. In this manuscript, benefits of ultra-performance liquid chromatography (UPLC) in which the stationary phase particle size may be reduced from 3.5 μm with a mobile-phase backpressure of 6000 psi in traditional analytical HPLC to a stationary phase particle size of 1.7 μm and a mobile phase backpressure of 15,000 psi in UPLC are reported. UPLC can more than double the chromatographic resolution and reduce each chromatographic run time by 10-fold, such that a complete analysis takes only 3 min per sample.

Improved particle-packed HPLC/MS microchips for proteomic analysis

The influence of packing process parameters (packing pressure, application of ultrasound) and the stationary phase particle size (3.5 and 5 μm) on the chromatographic performance of HPLC/MS chips was systematically investigated for proteomic samples. First, reproducibility and detection limits of the separation were evaluated with a low-complexity sample of tryptic BSA peptides. The influence of adsorbent packing quality on protein identification was then tested with a typical proteomics sample of high complexity, a human plasma protein fraction (Cohn fraction IV-4). All HPLC/MS chips provided highly reproducible separations of these proteomic samples, but improved packing conditions and smaller particle sizes resulted in chromatograms with narrower peaks and correspondingly higher signal intensities. Improved separation performance increased the peak capacity, the number of identified peptides, and thus the sequence coverage in the proteomic samples, particularly for low sample amounts.

Effect of analyte properties on the kinetic performance of liquid chromatographic separations

Advances in modern high-performance liquid chromatography (HPLC) have led to increased interest in the comparison of the ultimate performance limits of methodologies aimed at increasing the resolving power per unit time. Kinetic plot-based methods have proven invaluable in facilitating such evaluations. However, in bridging the gap between fundamental comparisons and the eventual practical applicability of kinetic performance data, the effect of analyte properties have thus far largely been neglected. Using pharmaceutical compounds as representative real-life analytes, it is demonstrated that noteworthy differences in the optimal kinetic performance of a chromatographic system are observed compared to data for common test compounds. For a given stationary phase particle size, higher optimal- and maximum plate numbers, corresponding to increased analysis times, are measured for pharmaceutical compounds. Moreover, it is found that the optimal particle size/maximum pressure combination depends on the analyte under investigation, with the beneficial range of efficiencies for small particles shifted towards higher plate numbers for drug molecules. It is further demonstrated that the pH of the mobile phase plays a crucial role in determining the kinetic performance of pharmaceutical compounds. These data clearly indicate that data for test compounds do not reflect the performance attainable for pharmaceutical compounds and highlights the importance of using real-life samples to perform kinetic evaluations.

Capillary Electrochromatography−Mass Spectrometry of Zwitterionic Surfactants

This work describes the on-line hyphenation of a packed capillary electrochromatography (CEC) column with an internally tapered tip coupled to electrospray ionization-mass spectrometry (ESI-MS) and atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) for the analysis of betaine-type amphoteric or zwitterionic surfactants (Zwittergent). A systematic investigation of the CEC separation and MS detection parameters comparing ESI and APCI is shown. First, a detailed and optimized manufacturing procedure for fabrication of the CEC-MS column with a reproducible internally tapered tip (7-9 microm) is presented. Next, the optimization of the separation parameters by varying the C(18) stationary-phase particle size (3 versus 1.5 microm), as well as mobile-phase composition including acetonitrile (ACN) volume fraction, ionic strength, and pH is described. The optimized separation is achieved using 3-microm C(18) packing with 75% ACN (v/v), 5 mM Tris at pH 8.0. Optimization for on-line CEC-ESI-MS detection is then done varying both the sheath liquid and spray chamber parameters while evaluating the use of random versus structured factorial table experimental designs. The more structured approach allows fundamental analysis of individual ESI-MS parameters while minimizing CEC and MS equilibration time between settings. A comparison of CEC-ESI-MS to CEC-APCI-MS using similar sheath and spray chamber conditions presents new insight for coupling of CEC to APCI-MS. The sheath liquid flow rate required to maintain adequate sensitivity is much higher in APCI source (50 microL/min) as compared to the ESI source (3 microL/min). The on-line mass spectra obtained in the full scan mode show that fragmentation in the two sources occurs at different positions on the Zwittergent molecules. For ESI-MS, the protonated molecular ion is always highest in abundance with minor fragmentation occurring due to the loss of the alkyl chain. In contrast, the APCI-MS spectra show that the highest abundant ion resulted by elimination of propane sulfonate from the Zwittergent molecule. A comparison of the sensitivity between the two sources in positive ionization SIM mode shows that CEC-ESI-MS provides an impressive limit of detection (LOD) of 5 ng/mL, which is at least 3 orders of magnitude lower than CEC-APCI-MS (LOD 100 microg/mL). Finally, the optimized CEC-MS methods comparing ESI and APCI are applied for separation and structural characterization of a real industrial zwittergent sample, Rewoteric AM CAS.

Analysis of the information in a preparative chromatogram for further optimization of the operating conditions

It was demonstrated how the most salient theoretical aspects of linear and non-linear elution liquid chromatography can be used, without the aid of sophisticated optimization software, to analyse the information in a preparative chromatogram. It is important. First, to be able to recognize whether a given preparative chromatogram was obtained under volume- or mass-overload conditions or both. This permits further optimization of the injection conditions (size, volume and concentration of the sample), depending on the preparative objectives, and improvement of the stationary phase particle size and of the mobile phase flow-rate. This approach can also provide insight into the performance characteristics of the injection device, the efficiency of the column packing and the stationary phase capacity. Some examples taken from the recent literature are discussed.

Experimental Characterization of Strongly Nonlinear Elution Peaks in Liquid Chromatography

Abstract The shape of nonlinear elution peaks was studied experimentally in various chromatographic modes and a wide sample size range encompassing the case where the distribution isotherm curvature is the prevailing factor of band broadening. It is shown that as sample size is varied, the tailing part of all peaks adjoins a common curve that can be fitted with an exponential function whose parameters are independent of mobile phase linear velocity and stationary phase particle size. The effect of solute capacity factor on these parameters was also investigated. These findings provide valuable help for the optimization of linear velocity, particle size, as well as sample size in preparative liquid chromatography under mass overload conditions.