Micellar liquid chromatographic green enantioseparation of racemic amino alcohols and determination of elution order

A micellar liquid chromatographic method was developed for the green enantioseparation of racemic amino alcohols using an aqueous solution of the mixed surfactants as an alternative for organic solvents. In this study, the derivatives of the amino alcohols were synthesized using highly reactive chiral esters of (S)-levofloxacin (Lfx) under microwave conditions, and an aqueous solution of the surfactants (Brij-35 and SDS) was used for the enantioseparation of the synthesized diastereomeric derivatives (DDs) of amino alcohols using reversed-phase HPLC. The activated ester of Lfx was synthesized by reacting with N-hydroxybenzotriazole and characterized using UV, IR, ¹H NMR, high-resolution mass spectrometry, and elemental analysis. The DDs of racemic amino alcohols were separated on a C₁₈ column using micellar LC. Chromatographic conditions were optimized by varying the concentration of the surfactants in aqueous solution and by varying the concentration and pH of the buffer. The green assessment score was calculated for the developed method (score: 82, an excellent green method). In addition, the density functional theory calculations were performed to develop the lowest energy-optimized structures of DDs. The method was validated according to the International Conference of Harmonization guidelines, and the retention factor (k), selectivity factor (α), resolution factor (R_S), limit of detection (0.198 ng mL⁻¹ or 0.291 pM mL⁻¹), and limit of quantification (0.594 ng mL⁻¹ or 0.873 pM mL⁻¹) were calculated.     

Direct injection analysis of hexamethylene bisacetamide in biological fluids by an HPLC column switching technique with a micellar mobile phase

Summary This paper describes the direct injection analysis of the anti-cancer drug hexamethylene bisacetamide (HMBA) in biological fluids by an HPLC column switching technique. The first chromatographic column, which provides for sample extraction and cleanup, employs a micellar mobile phase with SDS as the modifier. The second column, coupled on-line to the first, utilizes reversed-phase conditions for analysis. UV detection is employed at 210 nm. 282 samples from 12 cancer patients were analysed and good pharmacokinetics curves obtained. The drug gives recoveries of 94.0–100.9% with a relative standard deviation of 1.88%. A sample analysis is completed within 15 minutes. This method should be satisfactory not only for the analysis of HMBA but also, probably for other drugs in biological fluids.     

Financial heat machine

We consider dynamics of financial markets as dynamics of expectations and discuss such a dynamics from the point of view of phenomenological thermodynamics. We describe a financial Carnot cycle and the financial analog of a heat machine. We see, that while in physics a perpetuum mobile is absolutely impossible, in economics such mobile may exist under some conditions.     

汽车空调用冷凝器总成的分析与研究

1引言在汽车空调冷凝器性能评价中，流动与传热特性无疑占有重要位置，但它并非唯一评价指标。象其它热交换器一样，评价其是否具有应用价值，影响因素较多，例如：（1）以流动与传热为代表的热工性能；（2）可靠性与寿命评价；（3）材料与工艺性能；（4）制造成本；（5）体积、重量与噪音等指标。目前，汽车空调冷凝器分为三种：管片式、管带式和平行流式。许多文献认为，平行流式的热工性能最优，而管片式最欢，但这并不意味着平行流式肯定将成为我国汽车空调冷凝器的发展趋势。本文认为：（1）平行流式工艺复杂，所需材料近期内难以国产…     

New description of heterogeneity effects in adsorption from multicomponent solutions and liquid adsorption chromatography

General equations describing adsorption from solutions on solids and liquid adsorption chromatography with mixed mobile phases are formulated in terms of the bulk and surface activity coefficeints. Definition of the surface activity coefficients is extended; they describe nonideality of surface solution due to difference in molecular interactions of the components as well as nonideality of this solution generated by the adsorbent heterogeneity. It is shown that the above general equations predict simpler expressions known already in the literature.     

反相液体色谱中溶质保留行为的研究——保留行为与溶质及流动相性质的关系

本文从热力学乎衡的观点出发,导出了在一定的固定相和流动相中,描述保留行为与溶质性质关系的通用式,并通过实验及文献数据验证了该式,获满意结果。当固定相一定时,得出溶质保留值的对数1n k’与二元流动相中有机改性剂的组成呈二次函数关系,亦用实验验证了这种关系。讨论了三元体系中溶质的保留行为与流动相中两种有机改性剂间的关系,以及各种情况下影响色谱体系选择性的因素。     

Thin-layer chromatography with high-boiling mobile phases.1. Investigation of the flow of the high-boiling mobile phases

This paper considers some aspects of a new TLC technique using a molten mobile phase which is solid under ambient conditions. The flow of high-boiling mobile phase at elevated temperature in thin-layer chromatography has been investigated and it is shown that the equation Z_f² = kt is not applicable to migration of the high boiling mobile phase front. The flow stability of the high-boiling mobile phase is noted. It is suggested on the basis of studies of concentration profiles of the solidified mobile phases by scanning photometers that the shape of the mobile phase concentration profile be taken into account in calculation of R_f Values.     

Effects of liquid chromatography mobile phase buffer contents on the ionization and fragmentation of analytes in liquid chromatographic/ionspray tandem mass spectrometric determination

The effects of liquid chromatography mobile phase buffer contents on the ionization and fragmentation of drug molecules in liquid chromatographic/ionspray tandem mass spectrometric (LC/MS/MS) determination were evaluated for simvastatin (SV) and its hydroxy acid (SVA). The objective was to improve further the sensitivity for SV by overcoming the unfavorable condition caused by the formation of multiple major adduct ions and multiple major fragment ions when using ammonium as LC mobile phase buffer. Mobile phases (70:30 acetonitrile-buffer, 2 mM, pH 4.5) with buffers made from ammonium, hydrazine or alkyl (methyl, ethyl, dimethyl or trimethyl)-substituted ammonium acetate were evaluated. Q1 scan and product ion scan spectra were obtained for SV in each of the mobile phases under optimized conditions. The results showed that, with the alkylammonium buffers, the alkylammonium-adducted SV was observed as the only major molecular ion, while the formation of other adduct ions ([M + H](+), [M + Na](+) and [M + K](+)) was successfully suppressed. On the other hand, product ion spectra with a single major fragment ion were not observed for any of the alkylammonium-adducted SVs. The affinity of the alkylammoniums to SV and the basicity of the alkylamines are believed to be factors influencing the formation and abundance of molecular and fragment ions, respectively. Methylammonium acetate provided the most favorable condition among all the buffers evaluated and improved the sensitivity several-fold for SV in LC/MS/MS quantitation compared with that obtained using ammonium acetate buffer. Better precision for SV in both Q1 and SRM scans was observed when using methylammonium buffer compared with those using ammonium buffer. The mobile phase buffer contents did not seem to affect the ionization, fragmentation and chromatography of SVA. The results of this evaluation can be applied to similar situations with other organic molecules in ionspray LC/MS/MS determination.     

Development of an HPLC Assay Method for Lenalidomide

Chromatographic separation of lenalidomide and its impurities was achieved on an Inertsil ODS-3 V column using a mobile phase consisting of a mixture of buffer, acetonitrile and methanol in the ratio 80:8:12 v/v. Degradation studies were performed on bulk samples of lenalidomide subjected to 0.5 N hydrochloric acid, 0.5 N sodium hydroxide, 10% v/v hydrogen peroxide, heating to 60 °C and UV light at 254 nm. Degradation was observed only under base hydrolysis conditions. The developed LC method gave a mass balance close to 99.5%, proving it to be suitable for stability studies and was validated with respect to linearity, accuracy, precision and robustness.