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  • Author or Editor: Robert Skibiński x
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Two new simple and accurate HPTLC methods for analysis of ziprasidone in capsules have been developed and validated. The first method was normal phase chromatography on silica gel F 254 HPTLC plates with hexane-dioxane-propylamine 1:9:0.4 ( v/v ) as mobile phase. The second method was reversed phase chromatography on RP8 F 254 HPTLC plates with tetrahydrofuran-pH 9.0 phosphate buffer 5:5 ( v/v ) as mobile phase. The silica gel plates were developed to a distance of 9 cm and the RP8 plates to a distance of 4.5 cm. Both analyses were performed in horizontal chambers and the plates were scanned by videodensitometry at 254 nm. The calibration plots were linear in the ranges 0.2–1.2 μg and 0.1–1.1 μg ziprasidone (per spot) for the NP-HPTLC and RP-HPTLC methods, respectively. The precision and accuracy of the methods were fully compared between themselves and also with the control method — classical densitometry at 243 nm. No significant differences were observed. The NP-HPTLC method was also used for study of the stability of ziprasidone in solutions. The methods can be used for routine quality-control analysis.

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The selectivity of the TLC separation of six new antidepressant substances has been investigated on silanized silica gel C 18 and on silica gel GF 254 . Optimization of the retention and selectivity of these compounds on reversed-phase plates (RP C 18 ) was performed by changing the pH and the concentration of organic solvent (methanol, acetonitrile, tetrahydrofuran) in the aqueous mobile phases. The substances were separated in horizontal chambers and the drugs were detected by use of a videoscanning system and illumination of the plates at λ = 254 nm. The drugs were also separated on silica gel GF 254 after solid phase extraction (SPE) from plasma. The best separation was achieved with benzene-acetone-ethanol-ammonia, 9 + 7 + 2 + 1 ( v/v ) as mobile phase.

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New, simple, rapid, and accurate thin-layer chromatographic methods have been established for determination of fluvoxamine and moclobemide in tablets. The drugs were chromatographed on silica gel 60 F 254 plates in horizontal chambers with benzene-acetone-ethanol-25% aqueous ammonia, 9 + 7 + 2 + 1 ( v/v ), as mobile phase. Densitometric detection and quantification were performed at λ = 249 nm and λ = 236 nm, respectively, for fluvoxamine and moclobe-mide; videodensitometric detection was performed at λ = 254 nm for both drugs. The range of linearity was 1–10 μg per spot for fluvoxamine and moclobemide for both methods. The relative standard deviation for determination of these antidepressants in pharmaceuticals was less than 2.5% for densitometry and less than 5.1% for videodensitometry. Recovery of fluvoxamine from tablets was 101.20% by use of densitometry and 98.96% by use of videodensitometry; recovery of moclobemide from tablets was 101.15% and 98.81% respectively.

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Ultra high-performance liquid chromatography (UHPLC) coupled with high-resolution quadrupole time-of-flight (Q-TOF) mass spectrometry was used for the preliminary photodegradation study of nine new generation psychotropic drugs. Based on the above method, two ionization sample modes — electrospray and atmospheric pressure chemical ionization were used for the registration of photodegradation profiles of the selected drugs. Multivariate chemometric analysis showed that electrospray ionization (ESI) method is more specific than atmospheric pressure chemical ionization (APCI) in high-resolution mass spectrometry (HR-MS) analysis of the analyzed psychotropic drugs. It was noticed that, with the use of ESI method, more potential photodegradation products can be identified and lower limits of its detection can be obtained.

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The lipophilicity and specific hydrophobic surface area of fourteen 1,3-benzoxazol-2(3H)-ones substituted in the benzene ring (fluoro-, chloro-, bromo-, dibromo-, amino-, and nitro-derivatives) were studied by reversed-phase thin-layer chromatography. Precoated C18 F254 plates and mixtures of methanol-water and aminoacetic acid buffer, pH 2.67 and 11.6, were used. The linear correlation between the volume fraction of methanol and values over a limited range was established with high values of correlation coefficients (r > 0.98).The obtained results were compared with computationally calculated partition coefficients values (AlogPs, ClogP, AB/logP, milogP, logPKOWIN, XlogP2, XlogP3) by principal component analysis (PCA) and appreciable differences between them were observed. The comparison of chromatographic behavior of the investigated 1,3-benzoxazol-2(3H)-ones with their isomeric analogs 1,2-benzisoxazol-3(2H)-ones shows significant differences between their R M0 values.

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Two new simple and accurate methods for determination of quetiapine in tablets-normal phase (NP) and reversed-phase (RP) high performance thin layer chromatography (HPTLC), each with densitometric and videodensitometric detection, were developed and validated. NP-HPTLC was developed with HPTLC silica F 254 plates and hexane-dioxane-propylamine 1:9:0.4 ( v/v ) as mobile phase. RPHPTLC was carried out using HPTLC RP8 F 254 plates with tetrahydrofuran-phosphate buffer, pH 9.0, 5:5 ( v/v ) as mobile phase. The silica gel plates were developed to a distance of 9 cm and RP8 plates to a distance of 4.5 cm. Both analyses were performed in horizontal chambers and scanned with a densitometer at 243 nm and a video-densitometer at 254 nm. Calibration plots were linear in the range 0.2–1.2 μg quetiapine per spot for NP-HPTLC and in the range 0.1–1.1 μg for RP-HPTLC. The precision and accuracy of the four methods were fully compared and no significant differences were observed. The methods can be used in routine pharmaceutical analysis.

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Two new, simple, rapid, and accurate thin-layer chromatographic methods have been developed for determination of fluoxetine in capsules and paroxetine in tablets. The drugs were chromatographed on silica gel 60 F 254 plates in horizontal chambers with benzene-acetone-ethanol-25% aqueous ammonia, 9 + 7 + 2 + 1 ( v/v ) as mobile phase. Densitometric detection was performed at λ = 218 nm and 293 nm for fluoxetine and paroxetine, respectively; video-densitometric detection was performed at λ = 254 nm for both drugs. The range of linearity was 2–10 μg per spot for fluoxetine and 0.5–8 μg per spot for paroxetine. The relative standard deviation for determination of these antidepressants in pharmaceuticals was less than 4.3% for densitometry and less than 4.9% for video-densitometry. Recovery of fluoxetine from capsules was 105.1% by use of densitometry and 104.3% by use of videodensitometry; recovery of paroxetine from tablets was 99.15% and 98.2%, respectively.

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In this study, the in vitro phase I metabolism of lacosamide was characterized with the use of ultra-high-performance liquid chromatography combined with high-resolution mass spectrometry (quadrupole time-of-flight). The use of two metabolism simulation techniques (photocatalysis and human liver microsomes) allowed the characterization of a polar metabolite of parent compound, not yet described. The experiment with the participation of HLM gave the ability to describe the full liver metabolic pathway of lacosamide. It has been proven that this molecule undergoes deacetylation, demethylation, and during liver tissue metabolism. Photocatalysis with the use of a TiO2 catalyst was proved to be a complementary technique in mimicking in vitro drug metabolism.

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The retention (R M) values of nine one-point adsorption model compounds: diphenylamine, indol, 2-naphtol, 1-naphtol, 1-naphtylamine, 4-toluidine, carbazole, 4-chloraniline, and thymol were investigated on silica gel using six modifiers: acetone, dioxane, hexane, isopropanol, methylethylketone, ethyl acetate, and tetrahydrofurane (in hexane). These compounds showed small but visible curvilinearity of dependence of R M vs. modifier concentration. This curvilinearity is very similar among the investigated compounds, so relative differences of extrapolated R M are almost the same (strictly intercorrelated) regardless of the regression technique used. We have compared several robust and weighted regression methods and investigated their impact on extrapolated values. It can be concluded that one should primarily consider weighted regression with 1/x weights during retention extrapolation. It seems to be a better alternative than classical regression (better extrapolation) and also better than polynomial approaches (better stability).

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