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1

Stress degradation studies on zolpidem tartrate using LC-DAD and LC-MS methods

Malesevic M., Zivanovic L., Protic A., Radisic M., Lausevic M., Jovic Z., Zecevic M.

Acta Chromatographica

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2014

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Vol. 26, no. 1

81--96

EN

The present study was designed to characterize the possible degradation products of zolpidem tartrate under various stress conditions according to International Conference on Harmonization (ICH) guidelines Q1A(R2). After exposure to light, heat, hydrolysis, and oxidation, the drug significantly degraded under photolytic and acid/base hydrolytic conditions. Degradation resulted in the formation of four key degradants. Degradation products were resolved from each other and the drug by employing an isocratic elution method on Luna C18 column with mobile phase consisting of methanol-10 mM ammonium acetate (68.4:31.6, v/v), wherein pH was adjusted to 5.4 with glacial acetic acid. To characterize the degradation products, a method was extended to LC-MS and a mass fragmentation pattern was established using single quadrupole. The degradants were identified as zolpacid, oxozolpidem, zolpaldehyde, and zolpyridine. Finally, the most possible degradation mechanism of zolpidem tartrate in different environments was proposed.

2

Simultaneous RP-LC analysis of 10-O-(N,N-dimethylaminoethyl)-ginkgolide B and three related impurities

Liu W.-Y, Yang X.-J, Li P., Feng F, Mao L.

Acta Chromatographica

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2011

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Vol. 23, no. 3

459--468

EN

10-O-(N,N-dimethylaminoethyl)-ginkgolide B (XQ-1) is an intermediate for synthesizing 10-O-(N,N-dimethylaminoethyl)-ginkgolide B methanesulfonate (XQ-1H), which is a novel ginkgolide B derivative and is being developed as a platelet-activating factor antagonist. A specific and rapid liquid chromatographic method was developed for the quantitative analysis of XQ-1 and its three related impurities, which were 10-O-(N,N-dimethylaminoethyl)-11,12-seco-ginkgolide B (imp-1), 10-O-(N,N-dimethylaminoethyl)-11,12-seco-3,14-dehydroginkgolide B (imp-2) and 10-O-(N,N-dimethylaminoethyl)-3,14-dehydroginkgolide B (imp-3) simultaneously in XQ-1 samples. Chromatographic separation was achieved on a CN band stationary phase, with the mobile phase consisting of methanol and 20 mM dipotassium hydrogen phosphate (pH 7.5) (50:50, υ/υ) in isocratic elution. The flow rate was 1.0 mL min-1 and detector was set at 220 nm. The method was optimized by the analysis of the samples generated during the forced degradation studies. The XQ-1, imp-1, imp-2, and imp-3 were completely separated within 15 min. The resolutions (Rs) amongst four target compounds were >2. The developed method was validated with respect to specificity, linearity, accuracy, precision, and robustness. The results indicated that the simultaneous LC determination method was readily utilized as a quality control method for XQ-1 sample.

3

Development and validation of a stability-indicating UHPLC method for assay of felbamate and related substances

Shetty S. K, Surendranath K. V, Kaja R. K., Satish J, Jogul J, Manitripathi U

Acta Chromatographica

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2010

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Vol. 22, no. 2

161--172

EN

A new, sensitive, stability-indicating, and cost and time-effective isocratic reversed-phase UHPLC method has been developed for quantitative analysis of felbamate, an antiepileptic drug, both in the bulk drug and in pharmaceutical dosage forms. Chromatographic separation of felbamate and its two impurities was achieved on a C 18 column with a simple buffer-methanol mobile phase; the run time was 8 min. Quantification was achieved by ultraviolet detection. Resolution between the impurities was >2.0. Response was a linear function of concentration over the range 0.1–3.0 μg mL -1, correlation coefficient >0.999, for felbamate and the impurities. The method is capable of detecting the two impurities at levels of 0.002% (0.02 μg mL -1) of the test concentration of 1.0 mg mL -1 (1 μL injection). The same sensitivity was achieved for all the degradation products formed during stress studies in which the drug was subjected to hydrolysis, oxidation, photolysis, and thermal degradation. Substantial degradation occurred under acidic and basic conditions. The stressed test solutions were assayed against felbamate working standard and the mass balance in each case was close to 100%, indicating the method is stability-indicating. The method was validated for linearity, accuracy, precision, and robustness in accordance with ICH Guidelines.

4

Stability-indicating LC method for determination of tadalafil in bulk drug and pharmaceutical dosage form

Mathpati M.M., Sangshetti J.N., Rane V.P., Patil K.R., Shinde D.B.

Chemia Analityczna

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2009

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Vol. 54, No. 4

679-689

EN

A novel stability-indicating LC assay method for quantitative determination oftadalafil in bulk drug and pharmaceutical dosage form in the presence of forced-degradation products was developed and validated. An isocratic reversed phase LC method was developed to separate the drug from its degradation products using a Zorbax SB-C18 column and water-acetonitrile mixture as a mobile phase. Detection was carried out at the wavelength of 235 nm. Tadalafil was subjected to stress conditions in order to perform its hydrolytic (acid, base), oxidative, photolytic, and thermal degradation. Degradation oftadalafil was observed in the presence of acid, base, and 30% H2O2. The drug was found to be stable under other stress conditions. The signals of degradation products were well-resolved from the main peak oftadalafil. Percentage recovery oftadalafil in pharmaceutical dosage form ranged from 98.89% to 101.25%. The developed method was validated with respect to linearity, accuracy (recovery), precision, specificity, and robustness. Forced degradation studies proved the stability-indicating power of the method.

PL

Opracowano i zwalidowano nową metodę ilościowego oznaczania tadalafilu za pomocą chromatografii cieczowej, w obecności produktów rozkładu, pozwalającą na ocenę stabilności surowca i formy farmaceutycznej. Zastosowanie kolumny Zorbax SB-C18 i izokratycznej mieszaniny woda —acetonitryl pozwalało na rozdzielenie leku od produktów rozkładu. Detekcję przeprowadzono przy długości fali 235 nm. Tadalafil poddano ekstremalnym warunkom w celu uzyskania hydrolitycznych (kwas, zasada), oksydatywnych. tbtolitycznych i termicznych produktów rozkładu. Rozkład tadalafilu obserowwoano w obecności kwasów, zasad i 30% H,O2. Lek okazał się trwały w pozostałych ekstremalnych warunkach. Sygnały produktów rozkładu były dobrze oddzielone od głównego piku tadalafilu. Odzysk w przypadku badania postaci farmaceutycznej wynosił od 98,89% do 10 l ,25%. Opacowana. metodę zwalidowano w zakresie liniowości, dokładności (odzysku), precyzji, specyficzności i odporności na zmiany warunków otoczenia. Badania rozkładu w warunkach ekstremalnych wykazały przydatność opracowanej metody do oceny stabilności leku.

5

Effect of carboxylic alfa-hydroxyacid and of temperature on rare earth element (REE) separation by ion chromatography

Dybczyński R. S., Kulisa K.

Chemia Analityczna

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2009

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Vol. 54, No. 3

437-457

EN

Separation of rare earth elements (REE) by ion chromatography employing three different α-hydroxyacids i.e. lactic (HLac), mandelic (HMand) and a-hydroxyisobutyric (a-Hlac) was studied using Dionex Ion Pac CS3 + CG3 column and Arsenazo III as a colour forming reagent. Special attention was paid to the effect of temperature on selectivity of separation and on column performance. Yttrium, which normally coelutes with dysprosium could be partly separated when using a-HIBA at elevated temperatures (65-75°C). Scandium, which at room temperature was eluted well ahead of the lanthanides (in all three systems investigated), at elevated temperatures when using HLac and especially HMand gradually moved into the region where lanthanides were eluted. Interestingly, plate heights calculated from elution curves of yttrium were smaller, and those of scandium higher, than the corresponding plate heights of the lanthanides. Significant contribution of the longitudinal diffusion in the stationary phase to the total zone spreading was observed. Comparison of the elution curves of all REE employing the same isocratic-gradient elution mode for the three acids at two different temperatures is presented.

PL

Wykonano badania wpływu rodzaju a-hydroksykwasu stosowanego jako eluent na rozdzielanie kationów pierwiastków ziem rzadkich (REE). Do rozdzielań REE zastosowano trzy a-hydroksykwasy: mlekowy (HLac), migdałowy (HMand) i a-hydroksyizomasłowy (a-HIBA). Badania przeprowadzono z wykorzystaniem wysokosprawnej kolumny kationo-wymiennej typu Dionex Ion Pac CS3 + CG3 i Arsenazo III jako barwnego odczynnika kompleksującego. Zbadano również wpływ temperatury na zmiany selektywności kationitu wobec rozdzielanych kationów REE oraz zmiany sprawności kolumny chromatograficznej.

6

Simultaneous analysis of eight bioactive steroidal saponins in Gongxuening capsules by HPLC-ELSD and HPLC-MS n

Liu X. X, Wang L., Yang J., Zhang T. T., Deng X. D., Wang Q.

Acta Chromatographica

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2009

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Vol. 21, no. 2

327--339

EN

Rapid high-performance liquid chromatographic methods with evaporative light scattering detection (HPLC-ELSD) and electrospray ionization multistage mass spectrometry (HPLC-ESI-MS n ) have been established and validated for simultaneous qualitative and quantitative analysis of eight steroidal saponins in ten batches of Gongxuening capsule (GXN), a widely commercially available traditional Chinese preparation. The optimum chromatographic conditions entailed use of a Kromasil C 18 column with acetonitrile-water (30:70 to 62:38, υ/υ ) as mobile phase at a flow rate of 1.0 mL min -1. The drift tube temperature of the ELSD was 102°C and the nebulizing gas flow rate was 2.8 L min -1. Separation was successfully achieved within 25 min. LC-ESI-MS n was used for unequivocal identification of the constituents of the samples by comparison with reference compounds. The assay was fully validated for precision, repeatability, accuracy, and stability, then successfully applied to quantification of the eight compounds in samples. The method could be effective for evaluation of the clinical safety and efficacy of GXN.

7

Accurate determination of trace amounts of lanthanum, yttrium and all stable lanthanides in biological materials by ion chromatography

Dybczyński R. S., Kulisa K., Danko B., Samczyński Z.

Chemia Analityczna

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2007

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Vol. 52, No. 4

549-564

EN

The analytical procedure for the isolation and preconcentration of La, Y and the lanthanides from biological materials and their determination by ion chromatography (1C) with the use of Dionex Ion Pac CS3 + CG3 column (sulfonic acid type), a-hydroxyisobutyric acid (a-HIBA) as an eluent, and PAR or Arsenazo III as color forming reagents, was elaborated. The scheme originally devised for NAA, involving microwave assisted digestion and multi step separation employing ion exchange and extraction chromatography columns was used to selectively recover REE fraction (without scandium) with 100% yield. The REE fraction was analyzed by IC at 25 and 70°C. The run at 70°C enabled resolution of Y and Dy peaks and as a result made possible quantitative determination of La, Y, and all lanthanides. Investigation on the mechanism of band spreading revealed that longitudinal diffusion in the stationary phase considerably contributed to the total plate height. Surprisingly, the plate height (H) calculated from Y peak was distinctly lower than H values of the adjacent lanthanides. The method was validated by analyzing several certified reference materials (CRMs).

PL

Opracowano metodę wydzielania z materiałów biologicznych i wstępnego zatężania La, Y oraz fantanowców do ich oznaczenia za pomocą chromatografii jonowej (1C). W tym celu zastosowano kolumnę Dionex Ion Pac CS3 + CG3 (z grupami kwasu sulfonowego), kwas a-hydroksyizomasłowy (a-HIBA) jako eiuent oraz PAR i Arsenazo III jako odczynniki dające reakcję barwną. Do selektywnego i praktycznie 100%-owego wydzielenia frakcji . ziem rzadkich (REE), bez skandu, z próbek mineralizowanych za pomocą energii mikrofalowej, wykorzystano wielostopniowy schemat rozdzielczy, oparty na chromatografii jonowymiennej i ekstrakcyjnej, opracowany początkowo dla potrzeb neutronowej analizy akty-wacyjnej (NAA). Analizę chromatograficzną REE prowadzono w temperaturach 25 i 70°C. W temp. 70°C okazaio się możliwe rozdzielenie pików itru i dysprozu, a tym samym ilościowe oznaczenie La, Y i wszystkich lantanowców. Badanie mechanizmu rozszerzania pasma wykazały, że dyfuzja podłużna w fazie stacjonarnej wnosi istotny wkład do wysokości półki teoretycznej (H). Nieoczekiwanie wartości H bliczone z piku itru były istotnie niższe niż wartości H dla sąsiadujących z nim lantanowców. Dokładność metody sprawdzono analizując kilka certyfikowanych materiałów odniesienia (CRMs).

8

Comparison of lipophilicity parameters of selected flavonoids determined by reversed-phase TLC and HPLC

Flieger J., Tatarczak M.

Chemia Analityczna

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2006

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Vol. 51, No. 5

739-750

EN

Reversed-phase (RP) TLC and HPLC behaviour has been examined for the series of flavo-noids using aqueous mobile phases wifh methano! and acetonitrile as organic modifiers. The effect of the type of the stationary phase was tested on two columns: Zorbax C18 and Chromolith RP-18, as well as on wcttable octadccyl silica-modified TLC plates. Retardation factors and chromatographic lipophilicity parameters have been determined. Experimental lipophilicity parameters: log kw, RMW, S, πo and calculated ones: log P.TLC and log PHPLC compared using calibration plots for sulfonamidc standard.

PL

Przebadano szereg flawonoidów metodami TLC i HPLC w odwróconym układzie faz używając jako fazy ruchomej roztworów wodnych z organicznymi modyfikatorami (acetonitryl i metanol). Stosowano kolumny Zorbax C18 i Chromolith RP-18 oraz piylki (do TLC) modyfikowane oktadecylem krzemionki. Wyznaczono współczynniki opóźnienia i chromatograficzne parametry lipofilowości. Wyznaczone doświadczalnie parametry: log kw, RMW, S, i π() oraz parametry obliczone: log PPHPLC i log PHPLC używając krzywych kalibrowania dla wzorców sulfonamidów.

9

HPLC separation of the mixture of tetracyclines and flumequine

Pilorz K., Choma I. M.

Chemia Analityczna

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2004

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Vol. 49, No. 5

749-758

EN

Tetracyclines and fluoroquinolones are used as human and veterinary antibiotics. Their extensive use as medicines and feed additives results in the appearance of their residues or metabolites in food. Therefore, it is important to develop a reliable method of detection of such residues. RP-HPLC isocratic separation of the mixture of four tetracyclines and flumequine has been proposed. The factors influencing retention of the analytes were investigated, including the content of the modifier, pH of the mobile phase, and concentration of the complexing agent. Addition of triethylamine was found to facilitate the separation. The best isocratic separation was obtained on C18 column packings with the methanol-oxalic acid mobile phase (40:60, v/v) with addition of triethylamine. pH of the aqueous phase was adjusted to 2.

PL

Tetracykliny i fluorochinolony są popularnymi antybiotykami w lecznictwie ludzi i zwierząt. Rezultatem ich powszechnego stosowania w weterynarii oraz jako dodatków do paszy jest pojawianie się w żywności niebezpiecznych dla zdrowia pozostałości tych leków oraz ich metabolitów. Istotne jest zatem opracowanie wiarygodnych metod oznaczania pozostałości antybiotyków w żywności. W niniejszej pracy przedstawiono izokratyczną metodę, rozdzielania czterech tetracyklin oraz flumechiny za pomocą metody RP-HPLC. Badano czynniki wpływające na retencję tych leków tj. zawartość modyfikatora, pH fazy ruchomej oraz stężenie czynnika kompleksującego. Stwierdzono, że dodatek trietyloaminy sprzyjał jakości rozdzielania. Najlepsze rozdzielenie czterech tetracyklin i flumechiny uzyskano przy zastosowaniu fazy C(18), oraz jako eluentu mieszaniny metanolu i kwasu szczawiowego (40:60, v/v) z dodatkiem trietyloaminy, pH fazy wodnej ustalono na 2.

10

Chromatographic retention of polybutadiene coated titania stationary phase using quantitative structure-retention relationships

Jiang Z. T., Zuo Y. M., Li R., Yu J. C.

Chemia Analityczna

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2004

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Vol. 49, No. 4

551-559

EN

Polybutadiene coated titania stationary phase (PBD-TiO2) for HPLC has been prepared by immobilisation of polybutadiene on porous spherical microparticles of titania. Chromatographic retention of PBD-TiO2 has been investigated using quantitative structure-retention relationships (QSRR). The logarithmic capacity factors (log k'(PBD-TiO2)) were measured on PBD-TiO2 in the methanol-water mobile phase (80:20, v/v) and compared with the nine structure descriptors of solutes. These studies were performed using the principal component analysis, cluster analysis, multiple linear regression and stepwise multiple regression. The results were compared with those obtained on the octadecyl silica stationary phase (ODS). The results obtained for PBD-TiO2 occurred to be very close to those for ODS. Hydrophobic interactions dominated in the retention of solutes. The retention of aromatic compounds on PBD-TiO2 stationary phase one can reasonably predict employing the empirical formula: log k'(PBD-TiO2) = 0.538 logP-1.099.

PL

Fazą stacjonarną dwutlenku tytanu pokrytego polibutadienem przygotowano przez immobilizację polibutadienu na porowatych mikrosferach tlenku tytanu (PBD-TiO2). Retencję chromatograficzna PBD-TiO badano stosując ilościowe zależności: struktura-retencja (QSRR). Logarytmy współczynników retencji zmierzone dla fazy PBD-TiO (log k(PBD ,Ti0(2) ) i fazy ruchomej metanol-woda (80:20) względem dziewięciu deskryptorów struktury, analizowano metodami: analizy głównych składowych (PCA), analizy skupień, liniowej regresji wielozmiennych (MLR), stopniowej regresji wielozmiennych (SMR) i porównano z danymi otrzymanymi dla stacjonarnej oktadecylowej fazy krzemianowej (ODS). Wyniki wskazują, że obie fazy stacjonarne są bardzo podobne i że oddziaływania hydrofobowe dominująw retencji analitów. Retencja związków aromatycznych na PBD-TiO(2) może być dobrze przewidzianą empiryczna zależnością log k'(PBDTi0 =0,538 IogP-1,099.