|Molecular Weight||165.236 g/mol|
Primesep C separates the active ingredients in the over-the-counter cold medicine, NyQuil. Succinate and bromate co-elute early, but acetaminophen, pseudoephedrine, doxylamine, and dextromethorphan are baseline resolved. A combination of cation exchange, complex formation, and hydrophobic interactions separate this mixture with a mobile phase of water, acetonitrile (MeCN, ACN) and triethylamine (TEA) phosphate with UV detection at 205 nm.
NyQuil is a cough medication produced by Procter&Gamble. It consists of acetaminophen, pseudoephedrine, doxylamine and dextromethorphan. Most of the analytical HPLC methods include either use of ion-pairing reagent or a gradient elution. Mixed-mode chromatography allows to replace long gradient method with short isocratic method. All four compounds are well separated within 3-5 minutes. Methods can be optimized for analysis of other cough composition containing general cough suppressants and pain killers. Method is robust and being validated at several drug companies.
Mixed-mode chromatography allows to separate various hydrophobic and hydrophilic drugs in one HPLC method. Presence of at least two mechanism of retention allows adjust selectivity of separation by changing three parameters: amount of acetonitrile, buffer concentration and buffer pH. Seven common drugs are separated on an Obelisc R trimodal HPLC column in gradient method. Method provides alternative selectivity to traditional reversed-phase chromatography. Operational range in which basic compounds are retained the most is from pH 3 to 5. At higher pH, longer retention can be achieved. Mixed-mode chromatography provides longer retention and better peak shapes for basic and acidic analytes. Method can be used in analysis of drugs and pharmaceuticals.
Common hydrophobic basic and hydrophilic basic drugs are separated by mixed-mode chromatography with greater selectivity and resolution than traditional reversed-phase column. Drugs are retained by combination of reversed-phase and cation-exchange mechanisms. Retention time is controlled by amount of acetonitrile, buffer concentration and buffer pH. Available detection techniques are based on buffer selection and include UV, Evaporative Light-Scattering Detector (ELSD), Corona (CAD), LC/MS, etc. This HPLC method can be adopted as general approach for analysis of drugs and pharmaceuticals.
Pseudoephedrine is a drug used in cough and cold compositions. One of the preservatives in solutions of pseudoephedrine is citric acid. Both compounds are hydrophilic in nature, with pseudoephedrine being a basic compound and citric acid an acidic compound. Separation of these two compounds is achieved on a Primesep N column. Compounds are separated by combination of HILIC, cation-exchange and anion-exclusion mechanisms. Pseudoephedrine and citric acid are monitored by UV. This HPLC method can be adopted as generic approach for analysis of pseudoephedrine and other hydrophilic drugs and preservatives in mixtures.
Motrin is cough and cold composition manufactured by McNeil PPC. It contains ibuprofen as non-steroidal anti-inflammatory drug (N-SAID) and pseudoephedrine as decongestant. Ibuprofen is hydrophobic acidic molecule and pseudoephedrine hydrophilic molecule. Pseudoephedrine does not retained well in reversed phase chromatography and requires the use of ion-pairing reagent. In the absence of ion-pairing reagent pseudoephedrine comes close to the void of the column even at low concentrations of acetonitrile, while ibuprofen shows strong retention by reversed-phase mechanism. Different properties of these two molecules require gradient elution and consequent equilibration of the column. In contrast when mixed-mode HPLC column, like Primesep 100, is used, the method can be isocratic, very short with no equilibration of the column. Ibuprofen is retained by strong reversed-phase mechanism and pseudoephedrine is retained by weak reversed-phase and strong cation-exchange mechanisms on Primesep 100 column. Retention time of hydrophobic molecule is controlled by amount of acetonitrile, and retention of hydrophilic basic molecule is controlled by the amount of buffer and buffer pH. Method can be UV, ELSD and LC/MS compatible with various additives to the mobile phase (TFA, ammonium formate or acetate, sulphate or phosphate buffers at various pH). This mixed-mode column can be used for analysis of other OTC drugs including mixtures of basic, acidic and hydrophobic compounds.
Application Notes: Neurotransmitters are polar basic compounds. Several HPLC techniques are used to analyze these hydrophilic molecules. The most common techniques are reversed-phase with ion-pairing reagents chromatography, ion chromatography, HILIC, and mixed-mode chromatography. SIELC developed a new approach of analysis, which is based on hydrogen bond interactions. Hydrogen-bonding offers unique and alternative selectivity to traditional approaches like reversed-phase, HILIC, ion-exchange, and mixed-mode chromatography. Our methods are fully compatible with ELSD, LC/MS and prep chromatography.
Application Columns: SHARC 1, 3.2x100 mm, 5 um, 100A. To learn more about SHARC 1 columns click here. To order this column click here. To see more chromatographic separations check our web site.
Application compounds: Pseudoephedrine, norephedrine, phenylephrine and norphenylephrine
Detection technique: UV, LC/MS