Simultaneous HPLC Analysis of Brompheniramine and Maleic Acid Counter-Ion on Heritage MA Column

Application description

The analysis of drugs and counterions usually requires two methods; one for the drug and another one for the counter-ion. This is true for basic and acidic drugs, as well as basic and acidic counter-ions. Brompheniramine is an antihistamine drug used in many cough and cold formulations (Nyquil, Avil, Dimetapp, Vick’s, etc). Brompheniramine is hydrophobic and basic in nature. Reversed-phase chromatography usually produces poor peak shape for this highly hydrophobic and basic compound due to the overloading of residual silanols on the surface of silica gel. Maleic acid is a common counter-ion used in drug production and various formulations. It has two carboxylic acid fragments with pKa of 1.94 and 6.22. It is very polar in nature due to the presence of two ionizable groups. We have developed a separation approach for analysis of basic drug and acidic counter-ion. The order of elution for brompheniramine and maleic acid can be changed by changing the amount of ACN, buffer pH and buffer concentration. The Heritage MA is a mixed-mode anion-exchange and cation-exclusion column. The basic ionizable group on the surface of silica gel shields silanols from interacting with the basic group in bromnehiramine, thus producing a perfect peak shape. The method is LC/MS compatible and no ion-pairing reagent is required to retain basic drug or acidic counter-ion retention time. The elution on the Heritage MA column is controlled by the amount of ACN, buffer concentration and buffer pH. The buffer pH, concentration control ion-exchange, ion-exclusion mechanisms and amount of ACN are controlling the hydrophobic retention of compounds analyzed on this mixed-mode column