RESUMEN
Each year, new psychoactive substances appear on the global drug market leading to constant changes. Most of these compounds with stimulating effect possess a chiral center, thus leading to two enantiomers with presumably different pharmacological properties. Among them, synthetic cathinones, often misleadingly traded as "bath salts," play an important role. There is little knowledge about the distinct effect of the enantiomers. The aim of this study was to test a commercially available Lux® i-Amylose-3 column by HPLC-UV for enantiorecognition of cathinone derivatives. Overall, 80 compounds were tested in normal phase mode, where 75 substances were separated under initial conditions. After method optimization, at least partial separation was achieved for the remaining compounds. The same set of substances was measured in polar-organic mode, where 63 analytes were resolved into their enantiomers under initial conditions with very short retention times. Both modes showed complementary results for the individual compounds. Furthermore, the tested methods proved to be suitable for differentiation of positional isomers, which can be useful for drug checking programs. All measurements were carried out under isocratic conditions, and intraday and interday repeatability tests were performed.
Asunto(s)
Alcaloides , Estereoisomerismo , Cromatografía Líquida de Alta Presión/métodos , Alcaloides/química , Alcaloides/aislamiento & purificación , Amilosa/química , Amilosa/análogos & derivados , PirrolidinasRESUMEN
In this paper enantiomers of selected chiral agrochemicals representing various structural classes were separated by using nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) employing a capillary column packed with silica particles containing immobilized amylose tris(3chloro-5-methylphenylcarbamate) (i-ADMPC) as a chiral selector (CS). Special attention was paid to peak dispersion in nano-LC and CEC instruments used in order to make comparison between these two techniques more reliable. Enantioseparations were studied utilizing methanol (MeOH) or acetonitrile-water (ACNH2O), both containing 5 mM of ammonium acetate as the mobile phases (MPs). The tested chiral stationary phase (CSP), containing 20% (w/w) of the neutral CS onto native silica, allowed the generation of sufficiently strong electroosmotic flow (EOF) to observe separation of enantiomers of studied agrochemicals in a reasonable time also in CEC mode. Modestly higher efficiencies and enantioresolutions were obtained in CEC than in nano-LC. Just a moderate preference of CEC over nano-LC in this particular study can be explained with a significant mass transfer resistance through the CSP that is caused due to high content of the CS in CSP.
Asunto(s)
Electrocromatografía Capilar , Agroquímicos , Amilosa/análogos & derivados , Amilosa/química , Electrocromatografía Capilar/métodos , Fenilcarbamatos/química , Dióxido de Silicio/química , EstereoisomerismoRESUMEN
A high-performance liquid chromatography-mass spectrometry (HPLC-MS) method was developed using a chiral column based on amylose tris(3-chloro-5-methylphenylcarbamate) for analysis of fipronil (a popular insecticidal nerve agent) and the related transformation products. The optimized method reached the goal of the simultaneous and complete separation of the multiple fiproles in a single run, including the chiral separation of fipronil enantiomers, fipronil metabolites, and photoproducts. The efficacy of such a method was demonstrated by its application in analyzing a series of fipronil samples exposed to sunlight conditions. In general terms, our study provided experimental approaches and an efficient analytical tool for monitoring the environmental fate of fipronil as well as its multitransformation products upon its applications either in agricultural or any other areas.
Asunto(s)
Insecticidas , Cromatografía Líquida de Alta Presión/métodos , Pirazoles , Estereoisomerismo , Espectrometría de Masas en TándemRESUMEN
In a recent study, opposite enantiomer elution order was observed for ketoprofen enantiomers on two amylose-phenylcarbamate-based chiral columns with the same chemical composition of the chiral selector but in one case with coated while in the other with an immobilized chiral selector. In the present study, the influence of this uncommon effect on method validation parameters for the determination of minor enantiomeric impurity in dexketoprofen was studied. The validated methods with two alternative elution orders for enantiomers were applied for the evaluation of enantiomeric impurity in six marketed dexketoprofen formulations from various vendors. In most of these formulations except one the content of enantiomeric impurity exceeded 0.1% (w/w).
Asunto(s)
Amilosa/química , Cromatografía Líquida de Alta Presión/métodos , Cetoprofeno/análogos & derivados , Fenilcarbamatos/química , Trometamina/química , Calibración , Técnicas de Química Analítica , Química Farmacéutica , Cromatografía , Composición de Medicamentos , Contaminación de Medicamentos , Cetoprofeno/química , Límite de Detección , Reproducibilidad de los Resultados , EstereoisomerismoRESUMEN
In this work, the use of different solvents and temperatures was explored, aiming to evaluate their influence on the enantioseparation of pesticides by HPLC in polar-organic conditions, employing a column containing immobilized amylose tris(3-chloro-5-methylphenyl-carbamate). The chiral separation of seventeen different pesticides widely used as herbicides, fungicides, insecticides and precursors were studied. The mobile phases included methanol, ethanol, iso-propanol, n-propanol and acetonitrile; either pure or containing additives such as diethylamine, trifluoroacetic acid, formic acid, acetic acid or mixtures thereof. We studied the influence of these eluents on chiral separation of those pesticides in terms of retention factor, enantioselectivity, enantioresolution and peak symmetry. Regarding temperature influence, evaluated within the range 5 - 40 °C, nearly all the compounds decreased their retention and selectivity factors with the increase in temperature, although the effect was dependent on the mobile phase solvent. Moreover, estimation of thermodynamic parameters was performed based on linear van´t Hoff plots.
Asunto(s)
Amilosa/análogos & derivados , Compuestos Orgánicos/química , Plaguicidas/química , Plaguicidas/aislamiento & purificación , Fenilcarbamatos/química , Temperatura , Amilosa/química , Cromatografía Líquida de Alta Presión , Estándares de Referencia , Solventes/química , EstereoisomerismoRESUMEN
In the present study separation of enantiomers of some chiral neutral, basic and weakly acidic analytes was investigated on the chiral stationary phase (CSP) made by covalent immobilization of amylose tris(3-chloro-5-methylphenylcarbamate) onto aminopropylsilanized (APS) silica in nano-liquid chromatography (nano-LC) in aqueous methanol or acetonitrile mixtures. It has been shown that similar to high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) this chiral selector is useful for separation of enantiomers of neutral, basic and acidic analytes also in nano-LC. In comparison to our previous research, in which the chiral selector (CS) was bonded on native silica, in this study, the CS was immobilized on APS silica in order to improve chromatographic performance towards basic analytes. In fact, some improvement was observed and surprisingly not only for basic but also for neutral and acidic analytes. Again, quite unexpectedly almost no electroosmotic flow (EOF) was observed in capillaries packed with ca. 20% (w/w) amylose tris(3-chloro-5-methylphenylcarbamate) immobilized onto APS silica although the same APS silica before attachment of chiral selector exhibited significant EOF. In order to generate EOF in the capillaries with the CSP and enable capillary electrochromatographic (CEC) experiment on it, the short segment of the capillary column was packed with APS silica without chiral selector. The EOF in such capillary enabled CEC experiment and some preliminary results are reported here.
Asunto(s)
Amilosa/análogos & derivados , Electrocromatografía Capilar/métodos , Cromatografía Liquida/métodos , Fenilcarbamatos/química , Dióxido de Silicio/química , Ácidos/química , Amilosa/química , Flavanonas/análisis , EstereoisomerismoRESUMEN
The chromatographic properties of a new coated amylose tris(3-chloro-5-methylphenylcarbamate) were evaluated in supercritical fluid chromatography for the separation of enantiomers of chiral 1-aryl-5-aryl-pyrrolidin-2-one derivatives, potential anticancer agents, and some commercial drugs. The mobile phase consisted of CO2-modifier mixtures with 30% of either methanol or ethanol, the flow rate was 3 mL/min. The column oven temperature was 40 °C and the outlet pressure was 15 MPa, in order to limit the compressibility of the CO2, thus limiting density variation along the column. The obtained results were then compared to those observed toward 3 other stationary phases: the coated amylose tris(3,5-dimethylphenylcarbamate), the immobilized amylose tris(3,5-dimethylphenylcarbamate) and the coated amylose tris(5-chloro-2-methylphenylcarbamate). It was shown that the new coated amylose tris(3-chloro-5-methylphenylcarbamate) was the most retentive column whatever the studied compounds, particularly for thalidomide and omeprazole with retention factors up to 73.3 and 29.5for the second enantiomer, respectively. Concerning the enantioselectivity, even most of the compounds are separated on all the four columns, the coated amylose tris(3-chloro-5-methylphenylcarbamate) allows the best resolution for most of the ten studied analytes (except omeprazole for which the resolution values are equal to 7.8 and 9.7 on the coated amylose tris(3-chloro-5-methylphenylcarbamate) and amylose tris(3,5-dimethylphenylcarbamate), respectively). Acting in complementary ways, the two chlorinated stationary phases permitted the complete separation of enantiomers of nine compounds out of the ten.
Asunto(s)
Amilosa/análogos & derivados , Cromatografía con Fluido Supercrítico/métodos , Amilosa/química , Antineoplásicos/análisis , Antineoplásicos/aislamiento & purificación , Carbamatos/química , Preparaciones Farmacéuticas/análisis , Preparaciones Farmacéuticas/aislamiento & purificación , Fenilcarbamatos/química , Pirrolidinonas/análisis , Pirrolidinonas/aislamiento & purificación , Dióxido de Silicio/química , EstereoisomerismoRESUMEN
In the present study separation of enantiomers of some chiral neutral and weakly acidic analytes was investigated on the chiral stationary phase (CSP) made by covalent immobilization of amylose tris(3-chloro-5-methylphenylcarbamate) onto silica in nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) in acetonitrile and aqueous acetonitrile. Few comparisons were made also between the enantioseparations in nano-LC and high-performance liquid chromatography (HPLC) with the chiral column of 4.6â¯×â¯250â¯mm dimension. Slightly better separation of enantiomers was observed in HPLC mode compared to nano-LC mode. It was shown that in the capillary columns packed with the CSP containing about 20% (w/w) of a covalently immobilized neutral chiral selector, amylose tris(3-chloro-5-methylphenylcarbamate), sufficient electroosmotic flow has been generated and enantioseparations with reasonable analysis time were performed also in CEC mode. It was shown once again that CEC offers a clear advantage over nano-LC from the viewpoint of plate numbers and peak resolution.
Asunto(s)
Amilosa/análogos & derivados , Amilosa/química , Electrocromatografía Capilar/métodos , Cromatografía Liquida/métodos , Nanopartículas/química , Fenilcarbamatos/química , Dióxido de Silicio/química , Cromatografía Líquida de Alta Presión/métodos , EstereoisomerismoRESUMEN
The separation of enantiomers of some chiral weak acids was studied in HPLC with chiral HPLC columns prepared by coating or covalent immobilization of the same chiral selector, namely amylose tris(3-chloro-5-methylphenylcarbamate) onto silica. After screening some representatives of arylpropionic acid derivatives, coumarins and barbiturates in hydrocarbon-alcohol type mobile phases, we studied the temperature dependence of separation parameters for ketoprofen and naproxen. Instances of reversal of the enantiomer elution order were observed function of column temperature, nature of polar modifier and its content in the mobile phase, as well as between the coated and covalently immobilized versions of the columns made with more-or-less the same chiral selector. Thermodynamic parameters such as Gibb's free energy, the standard molar entropy and the standard molar enthalpy of analyte transfer from the mobile to the stationary phase were calculated in some cases in order to explain the differences observed in the enantiomer separation ability and pattern of coated and covalently immobilized columns.