Optical rotation high-performance liquid

Initially, progress in this area was hampered by the lack of suitable analytical methods for chiral hydrocarbons. Early studies relied on optical rotation to determine enantiomeric excess (ee) values, but with the development of chiral gas chromatography (GC) and high-performance liquid chromatography (HPLC) columns, chromatographic methods have become more common. 

Restricted rotation, as surface conjestion increases, was postulated as being responsible for the observed optical rotations as the generations increase,1251 the possibility of racemization during amino acid acylation was also investigated. Amino acid isolation and high-performance liquid chromatography (HPLC) analysis following acidic hydrolysis of the asymmetric dendrimers revealed an enantiomeric excess > 96 %. 

Lloyd, D.K. Goodall, D.M. Scrivener, H. Diode-laser-based optical rotation detector for high-performance liquid chromatography and on-line polarimetric analysis. Anal. Chem. 1989, 61, 1238-1243. 

Goodall, D. M. and D. K. Lloyd, A note on an optical rotation detector for high-performance liquid chromatography, in Chiral Separations (D. Stevenson and D. Wilson, eds.). Plenum Press, New York, 1988, pp.131-133. 

The purity of protected amino acids is especially important for the synthesis of longer peptides. Standard techniques such as melting point determination, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and optical rotation are effective means of characterization. The optical purity can also be evaluated by high-performance liquid chromatography (HPLC) after derivatization with Marfey s reagent [216,217]. The advanced Marfey method refers to analysis by mass spectrometry after derivatization with Marfey s reagent [218-221]. Purification of side-chain protected amino acids by recrystallization is usually sufficient. 

Optical rotation and refractometric detectors were combined to characterize a series of dextrins by gel permeation chromatography and high performance liquid chromatography (HPLC). Gel permeation fractionates according to the hydrodynamic volume when adsorption is avoided/ and for this reason separates isomaltodextrins from linear maltodextrins. Specific rotation power [a] is directly obtained and confirms the chemical structure. Elution of cyclodextrins is also tested and discussed. HPLC reverse phase chromatography separates the anomers as shown by optical rotation and allows good resolution in the range of low DP. 

Edkins, T. J. and D. C. Shelly, Measurement concepts and laser-based detection in high-performance micro separation, in HPLC Detection Newer Methods (G. Patonay, ed.), VCH, New York, 1992, pp. 1-15. Goodall, D. M. and D. K. Lloyd, A note on an optical rotation detector for high-performance liquid chromatography, in Chiral Separations (D. Stevenson and D. Wilson, eds.). Plenum Press, New York, 1988, pp.131-133. 

The Cahn-Mangold-Prelog (R,S) system was used here to describe the chirality of molecules, and the enantiomeric excess (e.e.) to quantify the enantiomeric purity. The e.e. values, which are usually obtained from direct concentration determinations by high-performance liquid chromatography (HPLC) or gas chromatography (GC), have replaced the operational term optical purity in the last decades due to a high sensitivity of optical rotations to experimental conditions [17]. However, e.e. values that were calculated in several cases from the optical rotation and the dl system of a-amino acids based on the optical rotation were also adopted from the literature. On the other hand, neither the directions in which enantiomers rotated plane-polarized light (+ or —) nor specific rotations a were stated here. 

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