Irving R. Hunter

High-pressure liquid chromatography of steroids.

After a brief discussion of the merits and limitations of high-pressure liquid chromatography (HPLC) relative to other chromatographic methods, special problems in the application to steroids are discussed. Publications on HPLC of steroids are then discussed under the headings of individual classes, arranged generally in the order of increasing polarity.

High-pressure liquid chromatography of steroidal alkaloids.

High-pressure liquid chromatography was used to separate the following steroidal alkaloids: tomatidine, solanidine, solasodine, rubijervine, veratramine and jervine. The method was used to prepare crystalline solanidine from a crude mixture of aglycones obtained from Solanum chacoense, and to separate radioactive solanidine from extracts of potato plants fed with [4-C]cholesterol.

Liquid column chromatography of free sterols

Abstract Liquid column chromatography with an apolar sorbent—eluent system permits the separation of free sterols differing in the number and position of double bonds and in their alkyl side chains. The method is applicable tothe isolation of minute quantities of sterols from a large excess of closely related sterols.

Extension of flash exchange gas chromatography to ethyl esters of higher organic acids

Abstract The method of flash exchange to form esters of organic acids for gas chromatography has been modified for use with argon ionization detectors and extended to include organic acids of carbon content through C18. An aliquot of a mixture of potassium (or sodium) salts of organic acids and potassium ethyl sulfate in water is drawn into a hypodermic needle containing diatomaceous earth. The water is removed by warming the mixture in the needle in a convection oven at 100°. The needle is connected to a source of argon (15 p.s.i.g.) and then inserted into a pre-heated (275°) section of the gas chromatography column. As the exchange reactions to form ethyl esters take place, the products are swept into the column by the argon gas stream. Chromatograms of the esters contain sharp, well-separated peaks. Use of the method to confirm the identity of organic acids in fermented liquors used in bread production is described.

Determination of Solasodine in Fruits of Solanum Khasianum by a Combination of Chromatofuge and High-Pressure Liquid Chromatography

Abstract An extract of Solanum khasianum fruits was fractionated with a chromatofuge. The fraction containing solasodine was applied to a HPLC column and the effluent was monitored by UV. The peak height gave an accurate measure of the amount present. The efficiency and load capacity of the chromatofuge, as well as the accuracy and precision of the HPLC method were determined.

Isolation of Glycoalkaloids with the Chromatotron and Their Determination by High-Performance Liquid Chromatography

Abstract An extract of Solanum laciniatum leaves was fractionated with the Chromatotron. The glycoalkaloid fraction thus obtained was analyzed by reversed-phase HPLC. The load capacity of the Chromatotron with a 2-mm layer thickness is 600 mg (as determined with cholesterol) and the recovery of solasonine from the plant extract (as determined by HPLC) is 93–96%. The HPLC method permits the detection of as little as 1.5 μg solasonine or 3.5 μg solamargine with a linear detector response up to 375 μg for the former and 250 μg for the latter.

High-pressure liquid chromatography and ultraviolet spectrometry of ketonic C27 sterols

A method for the separation of ketonic C27 sterols was devised, based on high-pressure liquid chromatography (HPLC) and ultraviolet absorption (UV). The adsorption column contained silica gel, particle size 10 μm, and the eluents were dichloromethane/n-hexane/ethyl acetate (94∶5∶1) and dichloromethane/ethyl actate (99∶1) followed by dichloromethane/ethyl acetate (3∶1). The 5β-sterols were eluted before the 5α-analogs, sterols with isolated double bonds before conjugated carbonyl compounds, and ketones before hydroxy ketones. The effect of carbonyl groups on polarity depends on the position in the molecule and decreases in the order C-3>C-6>C-7. The ultraviolet absorption spectra of eleven sterols were determined, and their absorbance at 254 nm and at 280 nm was used for analyzing the column effluent with a dual detector system.