Kasylda Milczewska

Inverse gas chromatography as a source of physiochemical data

Inverse gas chromatography (IGC) is presented as a useful method for the examination of physicochemical properties of various materials. The advantages of IGC are presented. However, the uncertainties and sources of possible errors are also indicated and discussed.

Characterisation of mineral oil–polyester,mineral oil–poly-α-olefin mixtures by inverse gas chromatography

Poly-α-olefins and polyesters are the base stocks for the production of synthetic oils, and after mixing with mineral oils for semi-synthetic oils. Their behaviour at the temperatures found in a car engine at work (around 140 °C) is very important. The authors propose the use of an inverse gas chromatography (IGC) technique for qualification of their mixing properties. Information on the basic parameters for SN-200 oil (H-6), poly-α-olefin (PAO-6), ester (DB-51) and their mixtures H-6–PAO-6, H-6–DB-51 was obtained from standard, normalised methods. All examined base oils and their mixtures were placed in gas chromatographic columns and act as liquid stationary phases in the chromatographic process. The Flory–Huggins parameter χ∞12 was calculated from the retention data (IGC) for selected test solutes. For the mixtures H-6–PAO-6, H-6–DB-51 the values of Flory–Huggins parameter χ∞1(2,3) were calculated. The interactions between components of investigated mixtures were expressed by the Flory–Huggins interaction parameter χ∞23.

Relationship between surface properties determined by inverse gas chromatography and ibuprofen release from hybrid materials based on fumed silica

The ability of organic-inorganic hybrid materials to act as drug release-modifying agents was examined. In this study, ibuprofen, a non-steroidal anti-inflammatory drug was used as a model active pharmaceutical ingredient. The physicochemical properties of individual components of the hybrids, as well as these for two- and three-component systems were examined by inverse gas chromatography. The dispersive component of the free surface energy (γ(S)(D)), K(A) and K(D) parameters describing acidity and basicity of hybrid materials, respectively, as well as Flory-Huggins parameters were determined. χ(12)(∞) and [Formula: see text] parameters characterize the interactions between the hybrids and a test solute, or interactions between the drug and inorganic-organic materials, respectively. Additionally, Brunauer-Emmett-Teller (BET) method was used to characterize adsorption activity of the studied materials. The prepared hybrid materials were also characterized by Fourier transform infra-red (FTIR) spectroscopy. The release profiles of ibuprofen for the created hybrid materials were determined. Relationship between the physicochemical activity of hybrid materials and ibuprofen release was presented and discussed.

Inverse Gas Chromatographic Examination of Polymer Composites

Abstract Inverse gas chromatographic characterization of resins and resin based abrasive materials, polymerpolymer and polymer-filler systems, as well as dental restoratives is reviewed. Graphical Abstract

Inverse Gas Chromatography in Characterization of Composites Interaction

Inverse gas chromatography is a useful and quite versatile technique for materials’ characterization, because it can provide information on thermodynamic properties over a wide temperature range. The term “inverse” indicates that the stationary phase of the chromatographic column is of interest, in contrast to conventional gas chromatography. The chromatographic column contains the material under study. The method is simple, fast and efficient. It has been used for the characterization of hyperbranched polymers [Dritsas et al., 2008], block copolymers [Zou et al., 2006], polymer blends [Al-Ghamdi & Al-Saigh, 2000], nanocomposites [Boukerma et al., 2006], fillers [Milczewska & Voelkel, 2002], cement pastes [Oliva et al., 2002], fibers [van Asten et al., 2000] and crude oils [Mutelet et al., 2002].

The influence of direct compression powder blend transfer method from the container to the tablet-press on product critical quality attributes - a case study.

Abstract Objective: The aim of this article is to compare the gravitational powder blend loading method to the tablet press and manual loading in terms of their influence on tablets’ critical quality attributes (CQA). Significance: The results of the study can be of practical relevance to the pharmaceutical industry in the area of direct compression of low-dose formulations, which could be prone to content uniformity (CU) issues. Methods: In the preliminary study, particle size distribution (PSD) and surface energy of raw materials were determined using laser diffraction method and inverse gas chromatography, respectively. For trials purpose, a formulation containing two pharmaceutical ingredients (APIs) was used. Tablet samples were collected during the compression progress to analyze their CQAs, namely assay and CU. Results: Results obtained during trials indicate that tested direct compression powder blend is sensitive to applied powder handling method. Mild increase in both APIs content was observed during manual scooping. Gravitational approach (based on discharge into the drum) resulted in a decrease in CU, which is connected to a more pronounced assay increase at the end of tableting than in the case of manual loading. Conclusions: The correct design of blend transfer over single unit processes is an important issue and should be investigated during the development phase since it may influence the final product CQAs. The manual scooping method, although simplistic, can be a temporary solution to improve the results of API’s content and uniformity when compared to industrial gravitational transfer.

Preparation of hybrid materials for controlled drug release

Abstract Authors obtained hybrid organic–inorganic materials applied in sustained drug delivery. The materials are ibuprofen as a model drug, hydroxyapatite and three different polymers as supports. Influence of the type of employed polymer, an inorganic carrier, on the properties and drug release profiles was estimated. Flory–Huggins interaction parameters, the dispersive component of surface free energy and acid-base characteristic of the surface were used to assess the behavior of the composites in terms of drug release. The experiments were carried out with the use of inverse gas chromatography (IGC), Fourier transform infrared (FTIR) and ultraviolet (UV) techniques. FTIR and ATR-FTIR spectra were collected. The values of parameter obtained for all investigated materials (excluding poly(L-lactide) (PLA2)) indicate low or medium activity. The strongest interactions (the lowest values of the Flory–Huggins parameter) are observed for PLA2 composition, while the weakest interactions for systems with polyethylene glycol (PEG). Finally, drug release profiles are shown. For materials prepared with Eudragit® (EUD) and PLA, the release of drug was much smaller, which corresponds to lower values of Flory–Huggins parameter. The executed experiments allowed the estimation of the properties of prepared composites. Prepared materials present properties required in sustained drug release and may be successfully applied as drug delivery systems.