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Biomedical subjects

J Novaković

Publications and source records attributed to J Novaković.

7 recordsLinked to original sources
PubMed1998

Determination of free bile acids in pharmaceuticals by thin layer chromatography and high performance liquid chromatography.

High-performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD) and thin layer chromatography with flame ionization detection (TLC-FID) have been applied to the separation of five main free bile acids present in humans: cholic (CA), chenodeoxycholic (CDCA), deoxycholic (DCA), lithocholic (LCA) and ursodeoxycholic (UDCA) acid. HPLC separation was performed on Biospher Si 100 column using a mixture of n-heptane, isopropanol, ethylacetate, methanol and glacial acetic acid as a mobile phase. All the compounds were separated in less than 12 minutes by using a gradient elution mode. TLC-FID separation was performed on S-II Chromarods with a mixture of isooctane, ethylacetate and glacial acetic acid as a mobile phase. HPLC-ELSD method was applied to the determination of CDCA and UDCA in pharmaceuticals and their purity control when LCA, DCA and CA were considered as impurities.

Bile Acids and Salts↗
PubMed1996

Quantitative structure-chromatographic retention relationship study of six underivatized equine estrogens.

Underivatized estrone (ES), equilin (EQ), equilenin (EQN) and their corresponding 17 alpha-diols 17 alpha-estradiol (ESD), 17 alpha-dihydroequilin (DHEQ) and 17 alpha-dihydroequilenin (DHEQN) were separated by TLC, RP-HPLC and capillary GC. Their dipole moments (mu) and Randić's connectivity indices ((1)chi) were determined as parameters of importance for the separation. The number of H atoms was taken as an additive structural parameter of importance for the quantitative structure-chromatographic retention relationship study (QSRR). Principal component analysis (PCA) was applied in order to find similarities and dissimilarities between 9 TLC and 10 RP-HPLC systems. PCA indicated that proton donor-proton acceptor interactions play the most important role for the TLC and RP-HPLC separation. The two-dimensional non-linear map of PC variables showed that the keto-estrogens (ES, EQ and EQN) and the corresponding diols (ESD, DHEQ and DHEQN) form two separate clusters. The relationship between GC retention of equine estrogens characterized by Kováts indices (KI), their (1)chi and mu was expressed by the equation KI/100 = al(1)chi+ b/mu(2) + c. The biological activity of the estrogens was related to log 1/mu(2).

Animals↗
PubMed1990

Densitometric determination of conjugated oestrogens in the raw material and in pharmaceutical preparations.

A densitometric method for determination of complex mixtures of conjugated oestrogens in raw material and tablets was developed. The proposed procedure comprised hydrolysis of sodium sulphate esters of oestrone, equilin, 17 alpha-oestradiol, equilenin, 17 alpha-dihydroequilin and 17 alpha-dihydroequilenin, the chloroform extraction of free oestrogens and methyltestosterone (internal standard) and separation on TLC plates using chloroform-cyclohexane-dioxane-triethylamine (4.5:4.1:0.6, v/v) as the solvent for development. Quantitative assay was achieved by direct scanning of the oestrogen spots at 280 nm. The proposed method is simple, rapid, reproducible and adequate to control the content of conjugated oestrogens in the raw material and in pharmaceutical preparations.

Chromatography, Thin Layer↗
PubMed1989

Fluorodensitometric determination of conjugated estrogens in raw material and in pharmaceutical preparations.

A simple, rapid and reproducible fluorodensitometric method for the determination of conjugated estrogens has been developed. The proposed procedure includes the following steps: extraction, hydrolysis of sodium sulphate esters of estrone, equilin, equilenin and their 17-alpha-hydroxy derivatives, separation of the liberated 3-phenolic steroids and in situ measurement of fluorescence. The fluorescence emission was measured after spraying the spots of estrone and estradiol with 2,4-dinitrophenyl-hydrazine in sulphuric acid-ethanol medium and equilin and 17-alpha-dihydroequilin with phosphoric acid and sodium hydroxide solution, respectively. Equilenin and 17-alpha-dihydroequilenin were determined by measuring the native fluorescence. The method applied to the determination of raw material and tablets provided results which agreed well with the stated content and the requirements of USP XXI for conjugated estrogens.

Densitometry↗
PubMed1989

Spectrophotometric determination of procaine hydrochloride by means of iron (3+)-4-aminobenzohydroxamic acid complex.

A rapid, simple and reproducible method is presented, for the determination of procaine hydrochloride in bulk and in pharmaceutical preparations containing also corbadrine or caffeine. The method is based on the conversion of procaine into the corresponding hydroxamic acid which reacts with iron (III) forming a complex of violet colour stable at pH 2.0, with a maximum absorption at a wavelength of 540 nm, and with molar absorptivity (epsilon = 0.43 X 10(3) l mol-1 cm-1). The minimum detectable amount was 1.47 X 10(-4) M/l, and Lambert-Beer law is obeyed in the range 2.93 X 10(-4) - 4.106 X 10(-3) M/l. By the application of Bent-French method it has been established that the stoichiometric ratio of 4-aminobenzohydroxamic acid and iron (3+) in the complex is 3:1. No interference with degradation product of procaine (4-aminobenzoic acid) was observed.

Ferric Compounds↗
PubMedDate not supplied

Validation of a high-performance thin-layer chromatographic method for trace analysis for some generic drugs affecting gastrointestinal function.

To prevent cross-contamination between pharmaceutical products manufactured with the same equipment, cleanup procedures must be introduced before the manufacture of a new product begins. From an analytical point of view, it is crucial to select and validate a suitable analytical method to determine contaminants in the rinse water, swabs, and the placebo of the next product. High performance thin-layer chromatography (HPTLC) was chosen in our laboratory for this purpose and was optimized to meet the requirements of trace determination. The method was validated in terms of the limit of detection, limit of quantitation (LOQ), linearity close to the LOQ, sample preparation from the swab media and from the placebo of the next product made with the same equipment (recovery), precision, selectivity (interference from the swab and placebo matrixes), resolution (from related compounds), and robustness. The HPTLC method was applied to 2 different generic drugs affecting gastrointestinal function--the water-soluble H2-receptor antagonist ranitidine hydrochloride (RHCl) and the water-insoluble choleretic drug ursodeoxycholic acid (UDCA). Chromatography was performed on silica plates by using toluene-methanol-diethylamine (9 + 1 + 1, v/v/v) and n-heptane-ethyl acetate-glacial acetic acid (5 + 5 + 1, v/v/v) as the mobile phases for RHCl and UDCA, respectively. RHCl was measured in situ at 320 nm, whereas the detection of UDCA was performed at 502 nm after postchromatographic derivatization. The method was used for the determination of RHCl and UDCA in the swabs, the final rinse water, and the placebo batch after the cleanup process.

Chromatography, Thin Layer↗