Chiral detectors linearity

Supported liquid membranes (SLMs) consisting of 5% tri-n-octylphosphine oxide (TOPO) dissolved in di-w-hexylether/n-undecane (1 1) have been used in the simultaneous extraction of a mixture of three stUbene compounds (dienestrol, diethylstilbestrol, and hexestrol) in cow s milk, urine, bovine kidney, and liver tissue matrices [183]. The efficiencies obtained after the enrichment of 1 ng/1 stilbenes in a variety of biological matrices of milk, urine, liver, kidney, and water were 60-70, 71-86, 69-80, 63-74, and 72-93%, respectively. A new method to contribute to the discrimination of polyphenols including resveratrol with synthetic pores was proposed [184]. The work [185] evaluated two types of commonly available chiral detectors for their possible use in chiral method development and screening polarimeters and CD detectors. Linearity, precision, and the limit of detection (LOD) of six compounds (trans-stilbene oxide, ethyl chrysanthemate, propranolol, 1-methyl-2-tetralone, naproxen, and methyl methionine) on four common detectors (three polarimeters and one CD detector) were experimentally determined and the limit of quantitation calculated from the experimental LOD. trans-Stilbene oxide worked well across all the detectors, showing good linearity, precision, and low detection limits. However, the other five compounds proved to be more discriminating and showed that the CD detector performed better as a detector for chiral screens than the polarimeters. 

Linearity, precision, and the limit of detection (LOD) of trans-stilbene oxide and other compounds were investigated [89]. The authors investigated the second factor and evaluated two types of commonly available chiral detectors for their possible use in chiral method development and screening polarimeters and CD detectors. It was shown that frans-stilbene oxide worked well across all the detectors examined, showing good linearity, precision, and low detection limits. 

Fast chiral separations were carried out in a quartz chip using a linear imaging UV detector. Figure 6.11 shows the chiral separation of a tocainide derivative (an antiarrhythmic drug). UV imaging with a diode-array detector located along the 25-mm-long separation channel reveals the separation between the two enantiomers. Another chiral separation of pseudoephedrine was achieved in 13 s. The... 

HPLC provides reliable quantitative precision and accuracy, along with a linear dynamic range (LDR) sufficient to allow for the determination of the API and related substances in the same run using a variety of detectors, and can be performed on fully automated instrumentation. HPLC provides excellent reproducibility and is applicable to a wide array of compound types by judicious choice of HPLC column chemistry. Major modes of HPLC include reversed phase and normal phase for the analysis of small (<2000 Da) organic molecules, ion chromatography for the analysis of ions, size exclusion chromatography for the separation of polymers, and chiral HPLC for the determination of enantiomeric purity. Numerous chemically different columns are available within each broad classification, to further aid method development. 

A commercial CE system and a micropacked capillary was used to separate N—, O—, and S-containing heterocyclic compounds. Migration time reproducibility, linearity, and detector response was found to be comparable to HPLC. A study of the heterocyclic compound s elution order followed that predicted by the octanol-water partition coefficients (354). While chiral CEC provides improved resolution and higher efficiencies, additional work is needed since chiral CEC capillaries are not available commercially. The separation principles and chiral recognition mechanism for the separation of enantiomers have been reviewed (355). Furthermore, a comprehensive collection of drug applications and other compounds of interest has been reported (356). Direct enantiomeric separations by CEC were studied using a capillary packed with alpha-1-acid glycoprotein chiral stationary phase (357). Chiral resolution was achieved for enantiomers of benzoin, hexobarbital, pentobarbital, fosfamide, disopyramide, methoprolol, oxprenolol, and propanolol. The effects of pH, electrolyte concentration, and con-... 

The ease of forming the smectic mesophase by this class of side-group type liquid crystalline polymers has rendered a great possibility in synthesizing polymeric chiral smectic materials useful in non-linear optics, transducers, pyroelectric detectors and display devices (Chapter 6). The first polymer forming a chiral smectic-C phase was synthesized by Shibaev et al. (1984). It has a polymethacrylate main chain, a long polymethylene spacer, and a mesogenic unit attached at the end with a chiral moiety (polymer (3.60)). Since then, a lot of polymers with chiral mesophases have been synthesized and studied (Le Barny and Dubois, 1989). 

If efficiencies could be increased sufficiently, perhaps by using particles 1 pm in diameter, and techniques were developed to efficiently and reproducibly pack them, a single chiral stationary phase might be all that is necessary to separate the majority of enantiomeric mixtures. Such a system is, no doubt, part of the future. It must, however, be preempted by pumps and sample valves that can provide and tolerate the necessary high pressures. In addition, there must be detectors with sufficient sensitivity to furnish an adequate linear dynamic range of response to accommodate the inherent low loading capacity of such columns. 

The chiral columns used for liquid chromatography may also be used for supercritical fluid chromatography (SFC). SFC offers important advantages over HPLC and GC in the separation of enantiomers. First, SFC provides a higher resolution per unit of time than does LC, because the diffusion rates in the mobile phase and linear velocities are higher. Second, SFC chromatography is carried out at temperatures well below those used in GC. LC and GC detectors, such as FID (flame iruiized detectors) and mass spectrometry (MS), may also be applied to SFC (Chamberlain et al. 1998). 

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