Fourier transform infrared assay of membrane lipids immobilized to silica: leaching and stability of immobilized artificial membrane-bonded phases.
A nondestructive, sensitive assay to monitor the hydrocarbon content of silica-based chromatography particles has been developed. The assay requires a microscope accessory interfaced with a Fourier transform infrared (FTIR) spectrometer. For determining hydrocarbon content, undiluted alkyl-silica-bonded phases were pressed into a thin wafer. Hydrocarbon content was quantitated using the integrated hydrocarbon band intensity between 2995 and 2825 cm-1 [i.e., band area C-H] and the integrated silica oxide band intensity between 1945 and 1780 cm-1 [i.e., band area Si-O]. Plotting the [band area C-H]/[band area Si-O] ratio vs the carbon content determined by elemental analysis gave a correlation coefficient of r = 0.997. The FTIR assay was validated on 5-, 7-, and 12-microns silica particles using three different immobilized artificial membrane (IAM) silica-bonded phases. The utility of the FTIR assay in determining hydrocarbon content was demonstrated by evaluating hydrocarbon leaching from IAM phases exposed to mobile-phase solvents. The ability of organic solvents to leach hydrocarbon from IAM phases containing phosphatidylcholine (PC) as the immobilized ligand was chloroform greater than ethanol approximately methanol greater than ethyl acetate greater than methylene chloride greater than acetonitrile greater than acetone. Acetone and acetonitrile cause very little hydrocarbon leaching from HPLC-IAM.PC columns. When challenged with different mobile phases, IAM.PC columns perfused with mobile phase are more stable than IAM.PC-bonded phases stirred in mobile phases. IAM.PC contains lecithin linked to silica by amide bonds.(ABSTRACT TRUNCATED AT 250 WORDS)
Markovich
R J
RJ
Purdue University, School of Pharmacy, West Lafayette, Indiana 47907.
Stevens
J M
JM
Pidgeon
C
C
D002851:Chromatography, High Pressure Liquid; D005583:Fourier Analysis; D008053:Lipid Mobilization; D008563:Membrane Lipids / Q000032:analysis*; D008567:Membranes, Artificial; D012822:Silicon Dioxide; D013055:Spectrophotometry, Infrared / Q000379:methods
D008563:Membrane Lipids; D008567:Membranes, Artificial; D012822:Silicon Dioxide