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Chromatography

  • Please note that, as of 1 January 2016, Chromatography has been renamed to Separations and is now published here.
Chromatography is an international, scientific, peer-reviewed, open access journal of separation science published quarterly online by MDPI.
Note that from Volume 3, Chromatography has been renamed Separations.

All Articles (1,799)

Analysis of blood alcohol concentration is a routine analysis performed in many forensic laboratories. This analysis commonly utilizes static headspace sampling, followed by gas chromatography combined with flame ionization detection (GC-FID). Studies have shown several “optimal” methods for instrumental operating conditions, which are intended to yield accurate and precise data. Given that different instruments, sampling methods, application specific columns and parameters are often utilized, it is much less common to find information on the robustness of these reported conditions. A major problem can arise when these “optimal” conditions may not also be robust, thus producing data with higher than desired uncertainty or potentially inaccurate results. The goal of this research was to incorporate the principles of quality by design (QBD) in the adjustment and determination of BAC (blood alcohol concentration) instrumental headspace parameters, thereby ensuring that minor instrumental variations, which occur as a matter of normal work, do not appreciably affect the final results of this analysis. This study discusses both the QBD principles as well as the results of the experiments, which allow for determination of more favorable instrumental headspace conditions. Additionally, method detection limits will also be reported in order to determine a reporting threshold and the degree of uncertainty at the common threshold value of 0.08 g/dL. Furthermore, the comparison of two internal standards, n-propanol and t-butanol, will be investigated. The study showed that an altered parameter of 85 °C headspace oven temperature and 15 psi headspace vial pressurization produces the lowest percent relative standard deviation of 1.3% when t-butanol is implemented as an internal standard, at least for one very common platform. The study also showed that an altered parameter of 100 °C headspace oven temperature and 15-psi headspace vial pressurization produces the lowest MDL of 0.00002 g/dL when n-propanol is implemented as an internal standard. These altered headspace parameters have the potential to produce more precise and accurate BAC determination.

11 December 2015

Experimental setup using Agilent HS-dual column GC-dual FID for the detection of blood alcohol.

As column volumes continue to decrease, extra-column band broadening has become an increasingly important consideration when determining column performance. Combined contributions due to the injector and connecting tubing in a capillary LC system were measured and found to be larger than expected by Taylor-Aris theory. Variance from sigma-type and tau-type broadening was isolated from eluted peaks using the Foley-Dorsey Exponentially Modified Gaussian peak fitting model and confirmed with computational fluid dynamics. It was found that the tau-type contributions were the main cause for the excessive broadening because of poorly-swept volumes at the connection between the injector and tubing. To reduce tau-type contributions (and peak tailing), a timed pinch mode could be used for analyte injection.

1 December 2015

Variance values (obtained from an EMG fit and calculated with Equation 12) measured using the direct measurement method for 20, 29, 42, and 51 µm i.d. capillaries (1 m long) at flow rates ranging from 0.5–15 µL/min are shown in A. Separated sigma-squared and tau-squared values are shown in B and C, respectively. In B, straight-lines indicate values calculated using Taylor-Aris Theory (Equation 6).

Hyphenation of Field-Flow Fractionation and Magnetic Particle Spectroscopy

  • Norbert Löwa,
  • Patricia Radon and
  • Dirk Gutkelch
  • + 2 authors

Magnetic nanoparticles (MNPs) exhibit unique magnetic properties making them ideally suited for a variety of biomedical applications. Depending on the desired magnetic effect, MNPs must meet special magnetic requirements which are mainly determined by their structural properties (e.g., size distribution). The hyphenation of chromatographic separation techniques with complementary detectors is capable of providing multidimensional information of submicron particles. Although various methods have already been combined for this approach, so far, no detector for the online magnetic analysis was used. Magnetic particle spectroscopy (MPS) has been proven a straightforward technique for specific quantification and characterization of MNPs. It combines high sensitivity with high temporal resolution; both of these are prerequisites for a successful hyphenation with chromatographic separation. We demonstrate the capability of MPS to specifically detect and characterize MNPs under usually applied asymmetric flow field-flow fractionation (A4F) conditions (flow rates, MNP concentration, different MNP types). To this end MPS has been successfully integrated into an A4F multidetector platform including dynamic ligth scattering (DLS), multi-angle light scattering (MALS) and ultraviolet (UV) detection. Our system allows for rapid and comprehensive characterization of typical MNP samples for the systematic investigation of structure-dependent magnetic properties. This has been demonstrated by magnetic analysis of the commercial magnetic resonance imaging (MRI) contrast agent Ferucarbotran (FER) during hydrodynamic A4F fractionation.

25 November 2015

Three different flow cells to be used in the MPS spectrometer: (a) capillary quartz glass flow cell FC2 with helically coiled lower end. Flow cell with flexible tubing and (b,c) different effective receive coil volumes FC3L and FC3XL. (c) The construction allows for the exact and reproducible positioning of the coiled capillary in axial, transversal, and rotary position. The 2.5 windings in the bottom part of the flow cells are intended to enlarge the effective volume in the receive coil of the spectrometer.
  • Technical Note
  • Open Access

This article details the elements used in the method verification for the simultaneous high performance liquid chromatography (HPLC) assay of Pentoxifylline, Mupirocin, Itraconazole, and Fluticasone Propionate in Humco™ Lavare Wound base. The method was proven to be linear over 50%–150% of the nominal concentration of the standards. The method was proven to be accurate over 50%–150%, with 98%–102% recovery of the actives from spiked placeboes over that range. The method was shown to be specific to the analytes listed and precise, yielding acceptable results for system reproducibility and method repeatability. The method, as written, is considered to have been verified.

11 November 2015

Blank chromatogram.

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Chromatography - ISSN 2227-9075Creative Common CC BY license