HPLC Analysis of Midol Analgesic Formulation on Heritage MA Mixed-Mode Column

Application description

Midol is an over-the-counter (OTC) formulation used for menstrual cramping and other effects related to menstruation. It can also be used as a pain medication for other purposes. The active ingredients include acetaminophen, caffeine and pyrilamine. Acetaminophen (or paracetamol) is a relatively hydrophilic drug which is used to treat pain and fever. Caffeine is a relatively hydrophobic and neutral central nervous system (CNS) drug stimulant. It is considered a psychoactive drug. Pyrilamine or merylamine is a first-generation antihistamine medication. It is hydrophobic and basic in nature. The Midol formulation was analyzed on Heritage MA mixed-mode reversed-phase-, cation-exchange, anion-exclusion column. It retains caffeine and acetaminophen by the pure reversed-phase mechanism. Pyrilamine is retained by a combination of reversed-phase and cation-exclusion mechanisms. Pyrilamine, due to its basic nature, shows poor peak shape when traditional reversed-phase columns are used. This poor peak shape is attributed to the interaction of basic groups in pyrilamine with residual silanols on the surface of reversed-phase columns. This problem does not exist in mixed-mode chromatography where residual silanols are shielded from interacting with basic analytes by the presence of strongly basic groups on the surface. The retention time of caffeine and acetaminophen is controlled by the amount of ACN. Pyrilamine retention is controlled by the amount of acetonitrile, buffer concentration, and buffer pH. The method is robust and reproducible and can be used for the analysis of neutral, acidic, and basic compounds. Buffer choice depends on the detection technique and the desired pH of the mobile phase. Heritage MA column is compatible with 100% water and 100% ACN and can be used either in a single mode or in multiple modes, depending on the nature of analyte and buffer and mobile phase composition.