Lux Cellulose-2 Research Articles

Enantioselective Separation of Chiral N1-Substituted-1H-pyrazoles: Greenness Profile Assessment and Chiral Recognition Analysis.

Two commercialized polysaccharide-based chiral stationary phases, Lux cellulose-2 and Lux amylose-2, were examined for their chiral recognition ability on a set of 18 biologically active racemic 4,5-dihydro-1H-pyrazole derivatives by applying normal and polar organic elution modes. The results showed that all compounds were baseline-resolved with at least one of the used elution modes. The cellulose-based column was superior using polar organic mobile-phase compositions with analysis times close to 5 min and resolutions up to 18, while the enantiomer-resolving ability of amylose-based columns was greater using the normal elution mode with analysis times close to 30 min and resolutions up to 30. The competition between the analytes and the mobile phase constituents on H-bond interactions with the stationary phase has been discussed, and the impact of this competition on chiral recognition has been investigated. It was found that the polar organic mode is very beneficial for short run times and sharp peaks. The developed enantioselective high-performance liquid chromatography (HPLC) methods will be applied to monitor the stereoselective synthesis of compounds 1–18 or to develop preparative HPLC techniques for compounds 1–18, followed by stereospecific pharmacological studies for each enantiomer separately. Greenness profile assessment of the different elution solvents was carried out using the AGREE metric approach.

Chiral HPLC separation of enantiomeric blebbistatin derivatives and racemization analysis in vertebrate tissues

Simple and consistent chiral HPLC methods for the efficient separation of enantiomeric blebbistatin derivatives, namely parent compound blebbistatin and derivatives 4-nitroblebbistatin, 4-aminoblebbistatin, 4-dimethylaminoblebbistatin, and 4-t-butylblebbistatin were developed using cellulose tris(3,5-dimethylphenylcarbamate) as a stationary phase (Lux cellulose-1 column). Blebbistatin, 4-aminoblebbistatin, and 4-dimethylaminoblebbistatin racemates were well-separated in normal-phase HPLC conditions while 4-nitroblebbistatin and 4-t-butylblebbistatin were effectively separated in both normal- and reversed-phase HPLC conditions. Furthermore, the order of elution of enantiopure compounds was found to be independent of mobile phase compositions and conditions used, and solely depends on the interaction between the enantiomer and the chiral stationary phase. We found that despite the chiral center being present far from the D-ring in the blebbistatin structure, the D-ring substitutions prominently affect the chiral separation. Ex vivo racemization studies of the most popular blebbistatin derivative (S)-(–)-4-aminoblebbistatin in rat blood and brain tissues revealed that the compound does not convert into the inactive enantiomer. This confirms that (S)-(–)-4-aminoblebbistatin is a useful tool compound in cellular and molecular biology studies without the risks of racemization and degradation effects.

Determination of myclobutanil enantiomers in wheat and its processed products by ultraperformance liquid chromatography-tandem mass spectrometry based on a chiral stationary phase

建立了手性超高效液相色谱-串联质谱检测小麦及其加工制品中腈菌唑对映体残留的分析方法。样品经乙腈提取,N-丙基乙二胺(PSA)和C18净化,手性色谱柱Lux Cellulose-1(150 mm×2.0 mm, 3 μm)分离,质谱电喷雾正离子扫描(ESI+),多反应监测(MRM)模式进行检测。为准确定量,考察了小麦籽粒及其加工制品的基质效应,最终采用基质匹配校准法来补偿基质效应,并进行样品中腈菌唑对映体残留的校准定量。结果表明,腈菌唑的两个对映体得到良好的拆分。S-(+)-腈菌唑先出峰,R-(-)-腈菌唑后出峰,保留时间分别为4.34 min和5.13 min。S-(+)-腈菌唑和R-(-)-腈菌唑在小麦及其加工制品中的检出限均为0.2 μg/kg,定量限均为0.5 μg/kg。在0.5~25 μg/L范围内,腈菌唑对映体的峰面积与其质量浓度呈现良好的线性关系,相关系数(R2)均大于0.99。在对映体添加水平为5、50、100 μg/kg时,在小麦籽粒、麸皮、面粉、面团、馒头、面条、煮面水中,S-(+)-腈菌唑的平均回收率在82%~110%之间,RSD在0.9%~6.8%之间;R-(-)-腈菌唑的平均回收率在80%~109%之间,RSD在0.9%~6.8%之间。将该方法应用于实际样品的检测,在5份面粉、2份面条及2份馒头样品中均未检出腈菌唑对映体。该方法为手性农药腈菌唑对映体在初级农产品及其加工制品中的残留分析提供了有效的方法。

Supercritical fluid chromatography and liquid chromatography for isomeric separation of a multiple chiral centers analyte

The development of a chiral separation strategy has always been a challenge of crucial importance, particularly in the pharmaceutical field. Chromatographic methods have become popular, particularly High Performance Liquid Chromatography and Supercritical Fluid Chromatography from a preparative scale point of view. A bioactive compound bearing three stereogenic centers was entrusted in our laboratory and the aim of this work was to obtain the complete resolution of the eight stereoisomers. Nine different polysaccharide-based columns were tested in SFC under various carbon dioxide-based mobile phases. The use of a single chiral column Lux Cellulose-2 under 30% 2-PrOH in carbon dioxide, at a flow-rate of 1 mL/min, column temperature of 40°C, 120 bar outlet pressure allowed the obtention of eight peaks. To further improve the resolution of the two last isomers, two columns were serially coupled . The results obtained with the six different combinations are discussed. The tandem column supercritical fluid chromatography has demonstrated to be a useful technique to resolve the eight stereoisomers on Lux Cellulose-2//Cellulose-2 tandem of coupled columns with 30% 2-PrOH in carbon dioxide, at a flow-rate of 1 mL/min, column temperature of 40°C and 120 bar outlet pressure, despite a long analysis time. In order to compare the two methods (i.e supercritical and liquid), chiral liquid chromatography under polar aqueous-organic mode, polar organic mode and normal-phase mode, was implemented. The last mode allowed the full baseline resolution of the eight isomers on Cellulose-5 CSP, with 20% 2-PrOH in n-heptane at a flow-rate of 0.8 mL/min, at 25°C, λ=220 nm. The limits of detection and of quantification were determined for this method and the best values obtained for isomer 8 were equal to 2.84 and 9.37 nM respectively. Finally, a small-scale preparative separation of the multiple chiral centers compound was implemented on Cellulose-5 CSP within 10% 2-PrOH in n-heptane in order to study the stereoisomer elution order on Cellulose-2, Cellulose-5 and Chiralpak AD-H, under EtOH or 2-PrOH in n-heptane mobile phases, and partial reversal elution orders were observed.

Laboratory-Scale Semipreparative Enantioresolution of Phenylethanolic-Azole Heme Oxygenase-1 Inhibitors

In the present work, the development and application of two HPLC methods enabling the semipreparative enantioresolution of 1-(biphenyl-3-yl)-2-(1H-imidazol-1-yl)ethanol (1) and 1-[4-[(4-bromobenzyl)oxy]phenyl]-2-(1H-imidazol-1-yl)ethanol (2), two among the most potent and selective heme oxygenase-1 (HO-1) inhibitors known, are described. During the optimization step, different chiral stationary phase (CSP) features were evaluated, especially focusing the attention on (1) the type (electron-donating and electron-withdrawing) and position of the substituents in the phenyl moiety; (2) the physical coating or covalent immobilization of the modified polymer chain. Additionally, the effect of different types and amount of alcohol in the normal-phase eluent as well as of the column temperature, were investigated. For compound 1, Lux Cellulose-1 CSP containing cellulose tris(3,5-dimethylphenylcarbamate) was identified as the optimal choice in combination with a mobile phase consisting of n-hexane/ethanol—85/15 (v/v). Conversely, for compound 2, Lux Cellulose-2 CSP containing the cellulose tris(3-chloro-4-methyl phenylcarbamate)-based chiral selector was identified as the optimal choice, running the analysis with a n-hexane/ethanol/2-propanol—80/15/5 (v/v/v) mobile phase.

Enantioseparation and dissipation monitoring of oxathiapiprolin in grape using supercritical fluid chromatography tandem mass spectrometry.

Oxathiapiprolin is a chiral fungicide used in China for the prevention and treatment of grape downy mildew, but its potential risk could be inaccurately assessed without distinguishing its enantiomers. In this study, an effective and sensitive chiral analytical method was first established for quantification of oxathiapiprolin enantiomers using supercritical fluid chromatography tandem mass spectrometry. Baseline separation for oxathiapiprolin enantiomers was achieved for less than 3min by using a Lux Cellulose-2 chiral column with the resolution of 1.51. The elution order of the eluting enantiomers was identified as (-)-oxathiapiprolin and (+)-oxathiapiprolin by an optical rotation detector. The grape samples were extracted by QuEChERS method, with the average recoveries of each enantiomer in grapes were in the range of 88.1-111.8% and the relative standard deviations were less than 18.9%. The enantioselective analysis of the dissipation of oxathiapiprolin in field grape samples showed that (-)-oxathiapiprolin was dissipated faster than (+)-oxathiapiprolin. The results indicate that this proposed method could provide data support for the risk assessment of oxathiapiprolin in agricultural produces in a more accurate way.

Enantioseparation and stereoselective dissipation of the novel chiral fungicide pydiflumetofen by ultra-high-performance liquid chromatography tandem mass spectrometry

Pydiflumetofen is a novel and efficient broad-spectrum chiral fungicide consisting of a pair of enantiomers. A simple and sensitive chiral analytical method was established to determine the enantiomers of this chiral fungicide in food and environmental samples by ultra-high-performance liquid chromatography tandem triple quadrupole mass spectrometry (UHPLC-MS/MS) using QuEChERS method coupled with octadecylsilane-dispersive solid-phase extraction (C18-dSPE) as extraction procedure. The specific optical rotation and the absolute configuration of the enantiomers were identified by polarimetry and electronic circular dichroism (ECD). The elution order of the pydiflumetofen enantiomers on Lux Cellulose-2 was S-(−)-pydiflumetofen and R-(+)-pydiflumetofen. The average recoveries of eleven matrices ranged from 71.3% to 107.4%. The intraday relative standard deviations (RSDs) were less than 11.8%, and the interday RSDs were less than 12.6% for the two enantiomers. Stereoselective dissipation in pakchoi and soil were observed: S-(−)-pydiflumetofen was degraded faster than R-(+)-pydiflumetofen in pakchoi, causing the enantiomer fraction (EF) of the enantiomers to change from 0.50 to 0.42 in 7 days. However, R-(+)-pydiflumetofen was degraded faster than S-(−)-pydiflumetofen in soil, causing the EF of the enantiomers to change from 0.49 to 0.52 in 21 days. This study provides a method for monitoring pydiflumetofen enantiomer residues, which is crucial for improving risk assessments and the development of chiral pesticides.

Enantioselective residue analysis of oxathiapiprolin and its metabolite in tea and other crops by ultra-high performance liquid chromatography-tandem mass spectrometry.

Oxathiapiprolin is the first chiral piperidinyl thiazole isoxazoline fungicide developed to control downy mildew and other diseases, and there were no prior reports on its enantiomeric residue. In this study, a modified quick, easy, cheap, effective, rugged, and safe extraction and purification method followed by ultra-high performance liquid chromatography-tandem mass spectrometry determination was first developed and validated for the residue analysis of oxathiapiprolin enantiomers and its metabolite IN-E8S72 in green tea and other crops. Oxathiapiprolin enantiomers and IN-E8S72 were separated on a chiral Lux Cellulose-3 column with the use of 0.1% formic acid in acetonitrile and 5mmol/L ammonium acetate in water as mobile phases. IN-E8S72 was eluted first, followed by (-)-oxathiapiprolin, and then (+)-oxathiapiprolin. The recoveries ranged from 53.3 to 125.3% with relative standard deviations ranging from 1.4 to 16.0%. The limits of quantification for (-)-oxathiapiprolin and (+)-oxathiapiprolin were 0.005mg/kg in romaine lettuce, head cabbage, potato, grape, and garlic, 0.01mg/kg in soybean and pea, and 0.025mg/kg in green tea and dry pepper. The limits of quantification of IN-E8S72 were twice those of (-)-oxathiapiprolin. Screening results with real market samples indicated that there was no enantiomeric excess in the oxathiapiprolin residue in romaine lettuce.

Enantioselective fate of mandipropamid in grape and during processing of grape wine.

Enantioselective monitoring of chiral fungicide mandipropamid enantiomers were carried out in grapes and wine-making process. The enantiomers of mandipropamid were separated on a Lux Cellulose-2 column and determined by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). The processing procedure included washing, fermentation, and clarification. Significant enantioselectivity was observed in grape under field conditions and during wine-making processing. The half-lives of R-mandipropamid and S-mandipropamid were 5.63days and 7.79days under field conditions 43.3h and 69.3h during wine-making processing, respectively. The EF values ranged from 0.498 to 0.283 in grape under field conditions, and the EF values were from 0.458 (0h) to 0.362 (312h) during the whole fermentation process. The results indicated that R-mandipropamid degraded faster than S-mandipropamid in grape under field conditions and during the fermentation process. The processing factors (PFs) were less than 1 for each procedure, and the PF ranged from 0.005 to 0.025 in the overall process, which indicated that the wine-making process can reduce mandipropamid residue in grape wine. The results of this study could help facilitate more accurate risk assessments of mandipropamid in table grapes and during wine-making process.

Chiral Separation and Determination of Etoxazole Enantiomers in Vegetables by Normal-Phase and Reverse-Phase High Performance Liquid Chromatography.

The chiral separation of etoxazole enantiomers on Lux Cellulose-1, Lux Cellulose-3, Chiralpak IC, and Chiralpak AD chiral columns was carefully investigated by normal-phase high performance liquid chromatography and reverse-phase high performance liquid chromatography (HPLC). Hexane/isopropanol, hexane/n-butanol, methanol/water, and acetonitrile/water were used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase component, mobile phase ratio, and temperature on etoxazole separation were also studied. Etoxazole enantiomers were baseline separated on Lux Cellulose-1, Chiralpak IC, and Chiralpak AD chiral columns, and partially separated on Lux Cellulose-3 chiral column under normal-phase HPLC. However, the complete separation on Lux Cellulose-1, Chiralpak IC, and partial separation on Chiralpak AD were obtained under reverse-phase HPLC. Normal-phase HPLC presented better resolution for etoxazole enantiomers than reverse-phase HPLC. Thermodynamic parameters, including ΔH and ΔS, were also calculated based on column temperature changes from 10 °C to 40 °C, and the maximum resolutions (Rs) were not always acquired at the lowest temperature. Furthermore, the optimized method was successfully applied to determine etoxazole enantiomers in cucumber, cabbage, tomato, and soil. The results of chiral separation efficiency of etoxazole enantiomers under normal-phase and reverse-phase HPLC were compared, and contribute to the comprehensive environmental risk assessment of etoxazole at the enantiomer level.

Liquid chromatographic method for the simultaneous determination of achiral and chiral impurities of dapoxetine in approved and counterfeit products.

A reversed-phase high performance liquid chromatographic method was developed and validated for the simultaneous determination of the related substances of S-dapoxetine, including R-dapoxetine, (3S)-3-(dimethylamino-3-phenyl-1-propanol), S-3-amino-3-phenyl-1-propanol, 1-naphtol, 4-phenyl-2H,3H,4H-naphtho[1,2-b]pyran and 1-(2E)-Cinnamyloxynaphthalene. During the screening experiments seven different polysaccharide-type chiral stationary phases (amylose-based Lux-Amylose-1, Lux-i-Amylose-1 and Lux-Amylose-2, as well as cellulose-based Lux-Cellulose-1, Lux-Cellulose-2, Lux-Cellulose-3 and Lux-Cellulose-4) were tested in polar organic mode using a mobile phase consisting of 0.1% diethylamine in methanol, ethanol, 2-propanol and acetonitrile with 0.5mL min-1 flow rate at 20 °C. Best results were obtained on Lux Cellulose-3 column with the ethanol-based mobile phase. To increase the retention factor of two, early-eluting impurities, water was added to the mobile phase. In order to counterbalance the increased total analysis time, higher column temperature (40°C) and gradient elution, combined with flow-programming` was applied. Using the optimized conditions baseline separations were achieved for all compounds within 30min. The method was validated according to the International Council on Harmonization guideline Q2(R1) and applied to the analysis of an approved, tablet formulation and dapoxetine-containing products sold on the internet. As expected, in the case of the pharmacy-acquired product, all of the monitored impurities were below 0.1%. However, interesting results were obtained when internet-acquired samples were analyzed. These tablets contained racemic dapoxetine and/or high concentration of R-dapoxetine impurity. Based on this work polysaccharide-based chiral stationary phases can be successfully applied for the simultaneous determination of achiral and chiral impurities in reversed-phase mode applying gradient elution and flow-rate programs. The study further underlines the importance of not only achiral, but also enantiomeric quality control, whenever counterfeiting of a single enantiomeric agent is suspected.

Determination of the Enantiomeric Purity of Solriamfetol by High-Performance Liquid Chromatography in Polar Organic Mode Using Polysaccharide-Type Chiral Stationary Phases

Solriamfetol is a novel FDA approved enantiopure drug used for the treatment of excessive sleepiness associated with narcolepsy or obstructive sleep apnea. Only the active R-enantiomer is marketed, therefore, a method to determine the chiral purity is essential. Chiral separation of solriamfetol was performed by HPLC using polysaccharide-type chiral stationary phases in polar organic mode and described for the first time. Seven different polysaccharide-based chiral columns (Lux Amylose-1, Lux i-Amylose-1, Lux Amylose-2, Lux Cellulose-1, Lux Cellulose-2, Lux Cellulose-3 and Lux Cellulose-4) were employed for the separation of enantiomers using polar organic mode, with mobile phases consisting of 0.15% diethylamine in methanol (MeOH), 2-propanol (IPA) or acetonitrile (ACN). During the screening phase, the best results (Rs> 5, in less than 10 min) was obtained on a Lux Amylose-1 column with 0.15% diethylamine in methanol with an ideal elution order (the distomer eluted before the R-enantiomer). The effects of binary mobile phases on the resolutions and retention factors were also investigated containing different percentages of MeOH:ACN and MeOH:IPA. Using optimized parameters (Lux Amylose-1 column with 0.05% diethylamine in MeOH with 0.6 mL/min flow rate at 20 °C) high enantioresolution (Rs = 5.3) was achieved within 6 min. Thermodynamic analysis was performed and revealed an enthalpy-driven enantioseparation. The developed, isocratic HPLC method was validated according to current ICH guidelines and proved to be reliable, linear, precise and accurate for the determination of 0.1% S-enantiomer as a chiral impurity in R-solriamfetol.

Separation of enantiomers of chiral basic drugs with amylose- and cellulose- phenylcarbamate-based chiral columns in acetonitrile and aqueous-acetonitrile in high-performance liquid chromatography with a focus on substituent electron-donor and electron-acceptor effects

In this study, amylose- and cellulose-phenylcarbamate-based chiral columns with different chiral-selector (CS) chemistries were compared to each other for the separation of enantiomers of basic chiral analytes in acetonitrile and aqueous-acetonitrile mobile phases in HPLC. For two chemistries the amylose-based columns with coated and immobilized CSs were also compared. The comparison of CSs containing only electron-donating or electron-withdrawing substituents with those containing both electron-donating and electron-withdrawing substituents showed opposite results for the studied set of chiral analytes in the case of amylose and cellulose derivatives. Along with the chemistry of CS the focus was on the behavior of polysaccharide phenylcarbamates in acetonitrile versus aqueous acetonitrile as eluents. In agreement with earlier results, it was found that in contrast to the commonly accepted view, polysaccharide phenylcarbamates do not behave as typical reversed-phase materials for basic analytes either. In the range of water content in the mobile phase of up to 20–30% v/v the behavior of these CSs is similar to hydrophilic interaction liquid chromatography (HILIC)-type adsorbents. This means that with increasing water content in the mobile phase up to 20–30% v/v, the retention of analytes mostly decreases. The important finding of this study is that the separation efficiency improves for most analytes when switching from pure acetonitrile to aqueous acetonitrile. Therefore, in spite of reduced retention, the separation of enantiomers improves and thus, the HILIC-range of mobile phase composition, offering shorter analysis time and better peak resolution, is advantageous over pure polar-organic solvent mode. Interesting examples of enantiomer elution order (EEO) reversal were observed for some analytes based on the content of water in the mobile phase on Lux Cellulose-1 and Lux Amylose-2 columns.

Direct Enantiomeric Separation and Determination of Hexythiazox Enantiomers in Environment and Vegetable by Reverse-Phase High-Performance Liquid Chromatography.

In the present study, the direct enantiomeric separation of hexythiazox enantiomers on Lux cellulose-1, Lux cellulose-2, Lux cellulose-3, Lux cellulose-4, Lux amylose-1 and Chirapak IC chiral columns were carefully investigated by reverse-phase high-performance liquid chromatography (RP-HPLC). Acetonitrile/water and methanol/water were used as mobile phase at a flow rate of 0.8 mL·min−1. The effects of chiral stationary phase, temperature, thermodynamic parameters, mobile phase component and mobile phase ratio on hexythiazox enantiomers separation were fully evaluated. Hexythiazox enantiomers received a baseline separation on the Lux cellulose-3 column with a maximum resolution of Rs = 2.09 (methanol/water) and Rs = 2.74 (acetonitrile/water), respectively. Partial separations were achieved on other five chiral columns. Furthermore, Lux amylose-1 and Chirapak IC had no separation ability for hexythiazox enantiomers when methanol/water was used as mobile phase. Temperature study indicated that the capacity factor (k) and resolution factor (Rs) decreased with column temperature increasing from 10 °C to 40 °C. The enthalpy (ΔH) and entropy (ΔS) involved in hexythiazox separation were also calculated and demonstrated the lower temperature contributed to better separation resolution. Moreover, the residue analytical method for hexythiazox enantiomers in the environment (soil and water) and vegetable (cucumber, cabbage and tomato) were also established with reliable accuracy and precision under reverse-phase HPLC condition. Such results provided a baseline separation method for hexythiazox enantiomers under reverse-phase conditions and contributed to an environmental and health risk assessment of hexythiazox at enantiomer level.

Enantioselective behavior analysis of chiral fungicide tetraconazole in apples with UPLC-MS/MS

Chiral fungicide tetraconazole is widely used for apple production without the knowledge of its stereoselective degradation in apples based on the regional disparity and bagging of fruit technique. The present study was initiated to explore the stereoselective degradation of tetraconazole in Fuji apple from the three major apple-producing regions in China, with bagging and non-bagging of fruit treatments. A highly sensitive and efficient chiral separation method was developed for the analysis of tetraconazole enantiomers by UPLC-MS/MS with a Lux Cellulose-2 column. A considerable improvement was obtained for the retention time (<4 min), which reduced at least 70% as compared with previous researches. The persistence of tetraconazole stereoisomers in apples was prolonged with bagging treatment (T1/2, 33.94–64.49 days) than non-bagging treatment (T1/2, 11.88–39.79 days) in the three regions. The results indicated that the half-lives of tetraconazole enantiomers were significantly different in apples among the three regions (P < 0.01) with non-bagging of fruit treatment, while no obvious differences were found with bagging treatment between the three regions. The stereoselective dissipation of tetraconazole enantiomers in apples was not statistically different under non-bagging treatment, however, there were significant differences in degradation between enantiomers with bagging treatment (P < 0.05), in which (−)-S-tetraconazole degraded faster than (+)-R-tetraconazole in the three regions. Such behaviors of chiral pesticides should be regularly monitored due to its effects on the safety of food and risk assessment of pesticides, as well as the environmental pollution assessment.

Comparison of polysaccharide-based and protein-based chiral liquid chromatography columns for enantioseparation of drugs.

Two different columns-Lux Cellulose-1 and Chiralpak CBH-were evaluated for their chiral recognition abilities for eight drugs comprising three β-blockers, one antacid, and four cathinones in polar-organic elution mode and reversed-phase elution mode, respectively. The factors that affected the enantioseparation were tested and optimized to develop a suitable chiral separation method whose LC conditions are compatible with MS detection. In polar-organic elution mode with the Lux Cellulose-1 column, methanol and acetonitrile were tested as the main components of the mobile phase. In addition, the effects of adding isopropanol as organic modifier, acidic additives (formic acid), and basic additives (diethylamine) were evaluated. In reversed-phase elution mode with the Chiralpak CBH column, the effect of type and concentration of organic modifier (isopropanol, acetonitrile, and methanol), the mobile phase pH (6.4 and 5.0), and buffer concentration (1mM-20mM ammonium acetate) were evaluated. The best enantioseparation was achieved with the Chiralpak CBH column with a mobile phase composed of 5mM ammonium acetate aqueous (pH = 6.4)/methanol (95/5, v/v) at a flow rate of 0.1 mL/min and a temperature of 30°C. Under these conditions, six of eight chiral drugs were baseline separated.

Энантиоселективное определение S- и R- изомеров ибупрофена в плазме крови методом УЭЖХ-МС/МС

A new method of enantioselective determination of S- and R-isomers of ibuprofen in human plasma by ultraperformance liquid chromatography with tandem mass spectrometric detection using solid-phase extraction was developed. For enantioselective separation of ibuprofen isomers, a LUX Cellulose-3 chiral chromatographic column was used. Complete separation of the enathiomer peaks is achieved in the isocratic elution conditions with a mobile phase ratio of 0.05 % formic acid solution (%): methanol (%) = 30 : 70 (v/v) and a flow rate of 0.2 mL/min. The mass spectrometric detection was performed at negative ionization mode with multiple reaction monitoring, using the transitions at 205.13 &gt; 161.14 Da and 208.09 &gt; 164.03 Da for ibuprofen enantiomers and deuterated ibuprofen (internal standard), respectively. The method validation included the evaluation of the selectivity, linearity, lower limit of quantification (LLOQ), within-run and between-run precision and accuracy. The LLOQ for the two enantiomers was 100 ng/mL in plasma. The calibration curves showed good linearity of each enantiomers in the ranges from 100 to 60000 ng/mL. The method was successfully applied to a pharmacokinetic study of ibuprofen enantiomers in human plasma.

Stereoselective metabolism and potential adverse effects of chiral fungicide triadimenol on Eremias argus

Reptiles are an important part of vertebrates and are the primitive terrestrial vertebrates. However, lots of reptile species are endangered or susceptible to extinction. It is no doubt that contaminants are one of the important reasons for the decline of the lizard population. In this study, the selective metabolism of triadimenol (TN) in the male Eremias argus lizards and the toxic effects of TN on lizards were studied. TN chiral isomers were separated and detected by HPLC-MS/MS system with Lux Cellulose-1 column. Tissue distribution experiments showed the existence of stereoselectivity biotransformation of TN enantiomers among organs in lizards, and RR-TN preferentially emerged over the other enantiomers. The antioxidant enzymes (SOD, CAT, GST) activities and MDA content assays demonstrated that TN induced oxidative stress in most organs, especially in the liver, and the histopathology analysis showed the severe liver and testis damage caused by 14-day continuous TN gavage. The reproductive effects of TN-induced reflected in the increased sex hormone testosterone. This research confirms that TN could induce hepatic and reproductive toxicity of E. argus lizard.

Simultaneous determination of chiral and achiral impurities of ivabradine on a cellulose tris(3-chloro-4-methylphenylcarbamate) chiral column using polar organic mode

A high performance liquid chromatographic method was developed for the simultaneous determination of the related substances (R-ivabradine, dehydro-S-ivabradine, N-demethyl-S-ivabradine, ((S)-3,4-dimethoxy-bicyclo[4.2.0]octa-1,3,5-triene-7-yl-methyl)-methyl-amine) and 1-(7,8-dimethoxy-1,3,4,5-tetrahydro-2H-3-benzazepine-2-on-3-yl)-3-chloro-propane) of the heart-rate lowering drug, ivabradine. The separation capability of seven different polysaccharide-type chiral columns (Lux Amylose-1, Lux i-Amylose-1, Lux Amylose-2, Lux Cellulose-1, Lux Cellulose-2, Lux Cellulose-3 and Lux Cellulose-4) was investigated with a mobile phase consisting of 0.1% diethylamine in methanol, 2-propanol and acetonitrile. During the screnning experiments the best results were obtained on Lux Cellulose-2 (based on cellulose tris(3-chloro-4-methylphenylcarbamate) column with methanol with an ideal case, where all the impurities eluted before the S-ivabradine peak. Chromatographic parameters (flow rate, temperature and mobile phase constituents) were optimized by a full factorial screening design. Using optimized parameters (Lux Cellulose-2 column with 0.06% (v/v) diethylamine in methanol/acetonitrile 98/2 (v/v) with 0.45 mL/min flow rate at 12 °C) baseline separations were achieved between all compounds. The optimized method was validated according to the International Council on Harmonization Q2(R1) guideline and proved to be reliable, linear, precise and accurate for determination of at least 0.05% for all impurities in S-ivabradine samples. Method application was tested on a commercial tablet formulation and proved to be suitable for routine quality control of both chiral and achiral related substances of S-ivabradine.

Simultaneous determination of guaifenesin enantiomers and ambroxol HCl using 50-mm chiral column for a negligible environmental impact.

Chiral stationary phases are conveniently used for enantiomeric separation of drugs by liquid chromatography. Consumption of large volumes of hazardous solvents is considered as a common challenge for the sustainability of this technique. To this end, a columnar chromatography has been adopted using 50-mm-length stationary phases. The study comprised five Phenomenex Lux cellulose- and amylose-based columns for the separation of guaifenesin (GUA) enantiomers. In addition, an experimental design was used to optimize the gradient profile for the separation of racemic GUA and ambroxol HCl (AMB) binary mixture. The chromatographic method was achieved using Lux Cellulose-1 (50×4.6mm) as a chiral stationary phase and ethanol/water as a mobile phase with linear gradient elution of 20% to 70% ethanol in 6minutes at a flow rate of 1.0mLmin-1 and UV detection at 270nm. Linearity ranges were found to be 50 to 1000μgmL-1 and 15 to 450μgmL-1 for each GUA enantiomer and AMB, respectively. Environmental, health and safety tool was used to assess and compare greenness of the proposed and reported methods. Short column indeed reduces the environmental impact by decreasing waste by about 60% and utilizing only 1-mL ethanol in the mobile phase. The proposed method is a safer alternative for the simultaneous determination of drugs in their combined pharmaceutical formulation. The method has been validated and compared favorably with a reported one.