There are several groups of compounds which are used as active and inactive ingredients in various over-the-counter drug compositions. These compounds are different in nature and can be organic and inorganic. Most of the active ingredients are either hydrophobic basic, hydrophilic basic or hydrophilic neutral compounds. Basic active ingredients of cough and cold remedies used as salts of organic and inorganic acids. The most commonly used hydrophobic active ingredients are doxylamine, pyrilamine, chlorpheniramine, brompheniramine, and dextromethorphan. Doxylamine is an antihistamine drug, used to relieve symptoms of allergy, hay fever, and the common cold. Doxylamine is used in combination with other active ingredients to provide effective nighttime relief from cough and cold symptoms. Pyrilamine is an antihistamine drug, which targetsH1 receptors as an inverse agonist. Brompheniramine is an antihistamine drug of propylamine nature. Chlorpheniramine is an antihistamine used to treat symptoms such as allergic rhinitis. Dextromethorphan is a medication mostly used as a cough suppressant. It is a morphine type of medication with sedative, dissociative, and stimulant properties. Succinic acid is a hydrophilic diacid that is used as a counterion. Maleic acid is hydrophilic diacid which is used as a counterion. Both compounds have very limited retention even in RP-AQ columns.
Due to the strongly hydrophobic and basic properties of these compounds, they demonstrate a poor peak shape in traditional reversed-phase chromatography due to the overloading of residual silanol groups on the surface when these basic drugs are analyzed. In addition to this, hydrophilic counterions are not retained in RP because there is no mechanism of retention for these acidic hydrophilic compounds. Both problems were eliminated by using Heritage MA reversed-phase anion-exchange column. Column and method demonstrate high efficiency and good peak shape for acidic and basic analytes. It can be used to develop methods for various cough, cold, and congestion compositions without the use of ion-pairing reagents. Compounds are well retained by a combination of one or more mechanisms. The column is compatible with 100% ACN and 100% water as well as with most buffers with pH 1.5-7. Various additives to the mobile phase can be used based on the nature of samples and detection techniques.
Conditions of Experiment
||reversed-phase, cation-exclusion, anion-exchange
||4.6x150 mm, 3 um, 100A
||5% ACN with 30 mM AmFm pH 3
|Class of compounds:
||Amines, Aromatic base, Drug, Organic acid, Pyridine
|Nature of compounds:
||Acidic, Basic, Hydrophilic, Hydrophobic, Polar
Doxylamine, Pyrilamine, Succinic acid, Chlorpheniramine, Brompheniramine, Maleic acid, Dextromethorphan