Thermostability Determination of Antibiotics at High Temperatures by Liquid Chromatography-Mass Spectrometry

Abstract

Ciprofloxacin and tetracycline are broad spectrum antibiotics that have been used for decades to treat a wide variety of human bacterial infections. Currently, these antibiotics are routinely used to treat infections of the ear, nose, throat and urinary tract. They are also prescribed for pneumonia, bronchitis and the prevention and treatment of anthrax. Regulations for the use of prescription antibiotics usually specify that they should be stored between the temperatures of approximately 65-85 °F (18-29 °C). According to storage regulations, exposure to elevated temperatures could lead to degradation of the antibiotic and thus reduce its effectiveness. During routine use, prescription antibiotics are often inadvertently set aside in locations such as personal bags, cars, window sills, stove- tops, or outdoors. These storage locations can expose the antibiotics to high temperatures, particularly during the summer months. Therefore, there is a need to study the thermostability of these antibiotics in order to determine how severely they degrade in high temperature conditions. Liquid chromatography-mass spectrometry (LC-MS) has proven to be an excellent analytical tool for the detection of low concentrations of tetracycline, ciprofloxacin, and many other antibiotics in a variety of aqueous matrices. Using LC-MS, a method has been developed to monitor antibiotic samples that have been exposed to elevated temperatures for various periods of time. Thermal degradation in these samples was observed via a decrease in signal when compared to LC-MS data generated from laboratory standards. It was expected that the observed thermal degradation will increase with the amount of time the sample is exposed to elevated temperatures. Thermostability data will be presented at temperatures ranging from 90-200 °F (32-93 °C). Results from the study will be used to evaluate the current recommended temperature ranges for the storage of each antibiotic.