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Róbert Rajkó

Publications and source records attributed to Róbert Rajkó.

2 recordsLinked to original sources
PubMed2006

Physicochemical characterization of meloxicam-mannitol binary systems.

The dissolution behaviour of drugs remains one of the most challenging aspects in formulation development. The anti-inflammatory drug, meloxicam (ME) has poor water solubility. The object of this experiment was to improve the rate of dissolution of meloxicam in capsule form. In order to achieve this, mannitol was used as a carrier in different ratios, in physical mixtures and melted forms. Mannitol, a sugar alcohol, is a cheap and readily available excipient. Differential scanning calorimetry (DSC) and X-ray diffractometry were used to investigate the characteristics of meloxicam-mannitol binary systems. Multivariate curve resolution (MCR) as a chemometric method was applied to interpret the X-ray diffractograms. This is believed to be the first published use of this reasoning for this interpretation. According to the results, the amount of mannitol and the particle size of ME were important factors in the rate of dissolution. To the perfect dissolution of ME, the melt technology was used which resulted in mixed crystals. This technology was made by 10 parts of mannitol and 1 part of ME2 with about 6 microm in average particle size. The interaction (adhesion) between mannitol and ME for physical mixtures was not enough to the perfect dissolution.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2005

Towards the solution of the eluent elimination problem in high-performance liquid chromatography-infrared spectroscopy measurements by chemometric methods.

The high-performance liquid chromatography-infrared spectroscopy (HPLC-IR) technique utilizing on-line flow through cell (FTC) detection has an inherent practical problem: strong absorption bands of the eluent may mask valuable analytical regions of the IR spectrum. The experimentalists' answer to this challenge is physical elimination of the chromatographic eluent before spectroscopic detection, which however results in off-line measurement of spectra. In the present work, the capabilities of some chemometric algorithms using iteratively applied multi-way methods such as parallel factor analysis (PARAFAC) and PARAFAC2, developed with the aim of overcoming the problems of eluent elimination are examined and evaluated. Test calculations done on simulated liquid chromatographic infrared (LC-IR) data cubes have shown that although PARAFAC2 performs much better than the simple PARAFAC method, it does not give correct decompositions, just like multivariate curve resolution with alternative least squares (MCR-ALS) and related bilinear data based methods. In search for a better solution, a method named objective subtraction of solvent spectrum with iterative use of PARAFAC and PARAFAC2 (OSSS-IU-PARAFAC and OSSS-IU-PARAFAC2) has been developed. Calculations performed with the corresponding Matlab program developed by the authors and run with the appropriate functions in PLS_Toolbox yielded very promising results in evaluations of both simulated and real HPLC-IR data sets, after necessary data pretreatments.

Algorithms↗