Solid-phase extraction cleanup and liquid chromatography with ultraviolet detection of ephedrine alkaloids in herbal products.
A solid-phase extraction (SPE) cleanup and a liquid chromatographic (LC) method with UV detection is presented for analysis of up to 7 ephedrine alkaloids in herbal products. Alkaloids from herbal products are extracted with acidified buffer, isolated on a propylsulfonic acid SPE column, eluted with a high-ionic-strength buffer, and separated by LC with detection at 255 nm. LC separation is performed by isocratic elution on a YMC phenyl column with 0.1 M sodium acetate-acetic acid (pH = 4.8) containing triethyl-amine and 2% acetonitrile. Ephedrine alkaloids are completely separated in 15 min. Average recovery of 5 common alkaloids from 3 spiked matrixes is 90%, with an average relative standard deviation (RSD) of 4.4% for alkaloid spikes between 0.5 and 16 mg/g. Average quantitation of ephedrine and pseudoephedrine from 6 herbal products is 97% of declared label claims, and average quantitation of synephrine from an herbal dietary product is 85% of label claim (RSD, 3.2%). Recoveries of synephrine, norephedrine, ephedrine, pseudoephedrine, N-methylephedrine, and N-methylpseudoephedrine spiked in 4 herbal products averaged 95%. Results of ruggedness testing and of a second laboratory validation of the procedure are also presented.
Hurlbut
J A
JA
Metropolitan State College of Denver, Chemistry Department, CO 80217, USA.
Carr
J R
JR
Singleton
E R
ER
Faul
K C
KC
Madson
M R
MR
Storey
J M
JM
Thomas
T L
TL
D019342:Acetic Acid; D000097:Acetonitriles; D000470:Alkaloids / Q000032:analysis*; D017738:Alkanesulfonic Acids; D002021:Buffers; D002853:Chromatography, Liquid / Q000379:methods*; D004809:Ephedrine / Q000031:analogs & derivatives / Q000032:analysis*; D005021:Ethylamines; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D010665:Phenylpropanolamine / Q000032:analysis; D008517:Phytotherapy; D019346:Sodium Acetate; D013578:Synephrine / Q000032:analysis
D000097:Acetonitriles; D000470:Alkaloids; D017738:Alkanesulfonic Acids; D002021:Buffers; D005021:Ethylamines; C068559:propylsulfonic acid; D010665:Phenylpropanolamine; D019346:Sodium Acetate; C041707:N-methylephedrine; D004809:Ephedrine; D013578:Synephrine; D019342:Acetic Acid; C016162:triethylamine; C032159:acetonitrile