In this improved method for quantifying 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) in urine, after a multistep extraction of MHPG and internal standard (iso-MHPG) from 3.0 mL of urine, the compounds are separated on a C18 reversed-phase column and quantified by use of an electro-chemical detector. The isocratic chromatographic separation takes about 16 min. The mobile phase is phosphate buf...

I review the methodology of "high-performance" liquid chromatography as applied to therapeutic drug monitoring. Aside from direct injection of sample, sample cleanup involves miscible and immiscible organic solvent extractions, solid-phase extraction, and size separations. Column considerations are bonded phases, column dimensions, particle size, guard columns, stability, pH range, and reproduc...

We describe a procedure for measuring concentrations of cocaine in plasma by reversed-phase high-performance liquid chromatography, with ion-pairing. The procedure involves solvent extraction followed by back-extraction with dilute acid. The n-propyl ester of benzoylecgonine is used as an internal standard. An evaporation step is not required, and concentrations as low as 5 micrograms/L can be ...

Vitamin A deficiency is a health problem in Southeast Asia that can be corrected by feeding orange fruits and vegetables such as mango. Pumpkin is a traditional Korean food that is easy to store and is already believed to have health benefits. We extracted carotenoids from pumpkin by liquid-liquid extraction and by supercritical fluid extraction. We measured carotenoids by reversed-phase chroma...

We describe a simple method for extraction of estrogens that is efficient over the whole polarity range of estrogen metabolites in urine and plasma. A small reversed-phase C18 cartridge (Sep-Pak C18, Waters Associates, Inc.) is used for this purpose. After application of the biological fluid, followed by an aqueous wash, estrogens are eluted in 3 mL of methanol. For urine the pH should be kept ...

Oligoguanidines and oligobiguanides are in general use as antiseptics and disinfectants. They consist of complex mixtures of oligomers with different structures and varying chain length, so that a thorough chemical characterization of these products remains challenging. In the present work, high performance liquid chromatography was investigated as a tool for separation of oligoguanidines obtai...

Hydrolyzed urine with added ring-trideuterated normetanephrine and metanephrine is applied to wet C18-reversed-phase minicolumns. The "metanephrines" are eluted, dried, derivatized with pentafluoropropionic anhydride, and analyzed with the gas chromatograph-mass spectrometer. Ions for the nondeuterated and trideuterated compounds are monitored at ml z 458 and 461, respectively. For both normeta...