Octyl liquid chromatography

Figure 4.15 Ion-pair liquid chromatography of free amino acids using a column switching system. Column I, butyl-bonded silica gel, 50 x 4.6 mm i.d., 2, octyl-bonded silica gel, 50 x 4.6 mm i.d., and 3, octadecyl-bonded silica gel, 250 x 4.6 mm i.d. eluent, 0.01 m sodium acetate buffer (pH 5.6) containing 4 mM copper acetate and 0.8 mM sodium heptanesulfonate flow rate, 1 ml min-1 detection, UV 235 nm. Peaks 1, Tyr 2, Val 3, Met 4, His 5, Lys 6, lie, 7, Leu 8, Phe 9, Arg 10, Asp 11, Ser 12, Glu 13, Thr 14, Gly 15, Pro 16, Cys and 17, Ala. 1-9 were separated on column 1 and 10-17 were separated by a combination of columns 2 and 3.

Several improved stationary phase materials have been synthesized for reversed-phase liquid chromatography. One material is vinyl alcohol copolymer gel. This stationary phase is quite polar and chemically very stable however, it demonstrated a strong retention capacity for polycyclic aromatic hydrocarbons.45 9 Although stable octadecyl- and octyl-bonded silica gels have been synthesized from pure silica gel50,51 and are now commercially available, such an optimization system has not yet been built. Further experiments are required to elucidate the retention mechanism, and to systematize it within the context of instrumentation. 

David, W. et al.. Activity coefficients of hydrocarbon solutes at infinite dilution in the ionic liquid, l-methyl-3-octyl-imidazolium chloride from gas-liquid chromatography, /. Chem. Thermodyn., 35, 1335, 2003. 

Letcher, T.M. et al.. Determination of activity coefficients at infinite dilution of solutes in the ionic liquid l-butyl-3-methylimidazolium octyl sulfate using gas-liquid chromatography at the temperature 298.15 K, 313.15 K or 328.15 K, /. Chem. Eng. Data, 50,1294, 2005. 

At present, liquid chromatography is the method of choice for determining residues of quinolone antibacterials in edible animal products (Table 29.6). Separation is generally carried out on nonpolar reversed-phase columns containing octadecyl, octyl, phenyl, or polymeric sorbents. Either methanol or acetonitrile... 

At present, liquid chromatography has become the most widely used technique for determining anticoccidial drugs in edible animal products (Table 29.11). The separation of these drugs is generally done on nonpolar reversed-phase columns (octadecyl, octyl and phenyl), the preferred type being the octadecyl bonded silica. However, polar (389, 390, 392, 398, 400) columns have also been used for the determination of the polyether antibiotics in edible animal products. 

The use of reversed-phase liquid chromatography is growing in applications for separating mixtures of peptides. In this type of chromatography, the stationary phase is nonpolar, whereas the mobile phase is polar. The stationary phase is normally porous silica with bonded n-alkyl chains, mainly octadecyl but also octyl, hexyl, butyl, and propyl chains. 

Bereznitski, Y., Jaroniec, M., Kruk, M. and Buszewski, B. Adsorption characterization of octyl bonded phases for high performance liquid chromatography, J. Liq. Chromatogr. Related Technol, 1996, 19, 2767-2784. 

Rustum, A.M. Measurement of verapamil in human plasma by reversed-phase high-performance liquid chromatography using a short octyl column. J.Chromatogr., 1990, 528, 480-486... 

A computer-assisted system for predicting retention of aromatic compounds has been investigated in reversed-phase liquid chromatography. The basic retention descriptions have been derived from the studies on quantitative structure-retention relationships. The system was constructed on a 16-bit microcomputer and then evaluated by comparing the retention data between measured and predicted values. The excellent agreement between both values were observed on an octadecyl-silioa stationsu y phase with acetonitrile and methanol aqueous mobile phase systems. This system has been modified to give us the information for optimal separation conditions in reversed-phase separation mode. The approach could also work well for any other reveraed— phase stationsury phases such as octyl, phenyl and ethyl silicas. 

Retention in Reversed-Phase Liquid Chromatography For the octyl-bonded silica gel column ... 

R is usually octyl (CgHjy) or octadecyl (C18H37) and is the active site in the case of reversed-phase liquid chromatography (RPLC). The notation RP-18 means that the stationary phase is a siloxane-bonded silica with octadecyl groups on its surface. This stationary phase is nonpolar and thus is suitable for RPLC. 

Figure 3 Separation of a standard solution of d- and L-amino acids by chiral derivatization with ( + )-1-(9-fluorenyl)ethyl chioroformate foiiowed by high-performance liquid chromatography on an achiral column. Column Spherisorb octyl material (150 X 4.6 mm). Mobile phase acetonitrile (ACN), tetrahydrofuran (THF), and an acetic acid buffer (1.8 ml of glacial acetic acid in 11 of water pH adjusted to 4.35 with NaOH) Gradient 0-8 min, 8% ACN, 17% THF, 75% buffer (8/17/75) 8-22 min, 8/17/75 to 0/30/70 22-70 min, 0/30/70 to 0/50/50. Flow rate 0.8 ml min (Reprinted with permission from Einarsson S, Josefsson B, Moller P, and Sanchez D (1987) Analytical Chemistry 59 1194 American Chemical Society.)...

CMPO octyl(phenyl)-N,N-diisobutyl- carbamoylmethylphosphine HPLC high-performance liquid chromatography... 

Wang, I.-H. Moorman, R. Burleson, J. Simultaneous determination of dipropyl pyridine-2,5-dicarboxy-late, N-octyl bicycloheptene dicarboximide, piperonyl butoxide, and pyrethrins in pet shampoo hy reversed phase high-performance liquid chromatography, J.Liq.Chromatogr.Rel.Technol., 1996, 19,... 

Liquids. 6. Activity Coefficients at Infinite Dilution of Hydrocarbons, Alcohols, Esters, and Aldehydes in l-Methyl-3-octyl-imidazolium Tetrafluoroborate Using Gas-Liquid Chromatography. J. Chem. Eng. Data 2005, 50,1515-1519. 

Hydrocarbon Solutes at Infinite Dilution in the Ionic Liquid, l-Methyl-3-octyl-imidazolium Chloride from Gas-Liquid Chromatography. /. Chem. Thermodyn. 2003, 35,1335-1341. 

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