869568749

Edyta Grzelak. Barbara Mąjer-Dziedzic, Irena Choma

DEVELOPMENT OF A NOVEL DIRECT BIOAUTOGRAPHY-THIN-LAYER CHROMATOGRAPHY TEST: OPTIMIZATION OF GROWTH CONDITIONS FOR GRAM-NEGATIVE BACTERIA Escherichia coli

With the aim of developing a TLC-direct bioautography assay using Escherichia coli as test bacteria, various parameters influencing the viability of microorganisms on TLC plates were examined and checked for flumeąuine standards. The optimal times for preincubation and incubation of bacterial broth were 20 h at 37 degrees C and 2 h at 37 degrees C, respectively. The optimal viscosity of the broth was obtained for 0.05% agarose solution in Mueller-Hinton brotli. Various incubation times of the seeded TLC plates were also tested (5 h proved to be optimal). After incubation. the plates were sprayed with 0.2% aqueous [3-(4,5-dimethyldiazol-2-yl)-2,5 di-phenyltetrazolium bromide] (MTT) solution and incubated for 0.5 h at 37 degrees C. The precision of the method was evaluated by the repeatability (intraday assay) and intennediate precision (interday assay). The regression coefficients were 0.9977 and 0.9968. respectively, for intraday and interday curves. The calibration curves show good linearity in the rangę of 0.005-0.50 microg (0.5-50.0 microg/mL). The estab-lished LOD of flumeąuine eąualed 0.5 microg/mL, i.e., 5 ng flumeąuine in the spot. The developed direct bioautography test significandy enhances the sensitivity of tlie TLC method.

Publication: J. AOACInt. 94(5),1567-1572. In English, summary in English.

Wioletta Bąk, Irena Choma. Barbara Mąjer-Dziedzic

MATRIX SOLID-PHASE DISPERSION COMBINED WITH THIN-LAYER CHROMATOGRAPHY-DIRECT BIOAUTOGRAPHY FOR DETERMINATION OF FLUMEQUINE RESIDUES IN MILK: IMPROVEMENT OF THE METHOD

Flumeąuine is a fluoroąuinolone antibiotic, mainly used in veterinaiy and, to sorne extent, in human treatment. It can be found as a residue in inilk and in other food products. A new version of matrix solid-phase dispersion of inilk samples spiked with this antibiotic was developed. Tlus preseparation method was combined with thin-layer chromatography-direct bioautography to obtain semi-quantitative results. Escherichia coli were used as test bacteria. The various inodes of the procedurę were tested, and the one giving the best recoveiy of the antibiotics from milk was chosen.

Publication: J. Liąuid Chromatograph. Related Technol. 34, 1-8, 2011, fig. 4, tab. 2. In English, summary in English.

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