Quantitative analysis, chirality

Achiral lanthanide shifting reagents may be used to enhance the anisochrony of diastereomeric mixtures to facilitate their quantitative analysis. Chiral lanthanide shift reagents are much more commonly used to quantitatively analyze enantiomer compositions. Sometimes it may be necessary to chemically convert the enantiomer mixtures to their derivatives in order to get reasonable peak separation with chiral chemical shift reagents. 

Main biodegradation products of LAS, sulfophenyl carboxylates (SPCs), were separated by CE using a-cyclodextrin as the chiral selector [6]. The best separation of enantiomers was achieved with 60 mM a-cyclodextrin in a 20 mM citrate buffer at pH 4.0 with an uncoated fused-silica capillary. The method was applied for the qualitative and quantitative analysis of SPC in primary sewage effluents with a detection limit of 1 p,g L-1. 

Heteroaromatic sulfoxides and sulfones ligand exchange and coupling in sulfuranes and //Avo-substitutions, 49, 1 Heteroaromatic systems, Claisen rearrangements in, 42, 203 Heteroaromatics, quantitative analysis of steric effects in, 43, 173 Heterocycles aromaticity of, 17, 255 chiral induction using, 45, 1 containing the sulfamide moiety,... 

Grosman D. M. (1996) Southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera Scolytidae) quantitative analysis of chiral semiochemicals. PhD thesis. Viginia Polytechnical Institute. 

Ion Chromatography, edited by James G. Tarter 38. Chromatographic Theory and Basic Principles, edited by Jan Ake Jonsson 39. Field-Flow Fractionation Analysis of Macromolecules and Particles, Josef Janca 40. Chromatographic Chiral Separations, edited by Morris Zief and Laura J. Crane 41. Quantitative Analysis by Gas Chromatography, Second Edition, Revised and Expanded, Josef... 

Stereochemistry often is an integral component to both the chemical structure and the biological function of plant terpenoids. For volatile terpenoids, chiral GC stationary phases (48) provide the enantiomeric separation for quantitative analysis, and, provided an authentic standard of known absolute... 

Modern TLC can be conducted in both the normal-phase and the reversed-phase formats and can be extended to the separation of chiral compounds by modifying the stationary phase or mobile phase with chiral selectors. Using automated systems, performance equal to that achieved by HPLC is, in some cases, possible. Applications for quantitative analysis, including examples of stability-indicating and validated methods for pharmaceuticals, have been reviewed. 

The equilibrium of the enzyme acylation reaction can be shifted towards the synthesis of the amide by precipitation of the acylated product formed (Fig. 6). The racemic ethyl 3-amino-5-(trimethylsilyl)-4-pentynoate 3 is an insoluble liquid, whereas the (R)-phenylacetamide 10 is an insoluble solid. The racemic ethyl 3-amino-5-(trimethylsilyl)-4-pentynoate 3 was added to dilute hydrochloric acid. The pH of the reaction medium was then adjusted to 6. Phenylacetic acid (2 equiv.) was added and the pH of the medium was readjusted to 6. Soluble PGA (50 units/100 mg of racemic amine) was added, and the reaction was stirred at room temperature. After completion of the reaction, the pH of the reaction mixture was adjusted to 4. Filtration of the reaction mixture gave (R)-amide 10 in quantitative yield. Chiral HPLC analysis of this isolated amide showed the absence of (S)-amide. The pH of the filtrate was raised to 8, and the filtrate was extracted with ethyl acetate to obtain (S)-amine 11 (yield 90%) (Fig. 6). The chiral HPLC analysis indicated an R S ratio of 2 98. 

Enantioselective hydrogenation of ethyl pyruvate was carried out in a 300 ml stirred autoclave (Parr Instruments, Illinois) at 20 °C and the pressure kept constant at 60 bar with a high pressure H2 burette. Reaction rates were determined from the drop in H2 pressure measured in the burette. Conversion and enantiomeric excess were determined by quantitative analysis by a GC equipped with a chiral capillary column for enantiomeric separation (for details see [6]). 

It is an absolute requirement of all validated immunoassays, whether competitive or immunometric, that for accurate quantitative analysis the standard material used to calibrate the reaction is identical to the analyte. This may be difficult for several reasons, including the chirality of the analyte and its heterogeneity in terms of post-translational modification. 

The analysis of amino acids by GC-MS of suitable volatile derivatives is a well-established technique. Despite the availability of amino acid analyzers, GC-MS is still occasionally used because it is useful for qualitative and quantitative analysis of unusual (i.e., nonprotein) amino acids. GC-MS is also valuable for conducting studies of the racemization of amino acids during cooking or food processing, when used in conjunction with chiral GC columns and deuterium labeling. GC-MS methods are also often used for determining stable isotope labeled amino acids in nutritional, metabolic studies. ESI LC-MS may also be used for determining amino acids. 

While open tubular (OT) columns are the most popular type, both open tubular and packed columns are treated throughout, and their advantages, disadvantages, and applications are contrasted. In addition, special chapters are devoted to each type of column. Chapter 2 introduces the basic instrumentation and Chapter 7 elaborates on detectors. Other chapters cover stationary phases (Chapter 4), qualitative and quantitative analysis (Chapter 8), programmed temperature (Chapter 9), and troubleshooting (Chapter 11). Chapter 10 briefly covers the important special topics of GC-MS, derivatization, chiral analysis, headspace sampling, and solid phase microextraction (SPME) for GC analysis. 

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