Brazil

The development and validation of a multidimensional HPLC method using an on-line clean-up column coupled with amperometric detection employing a boron-doped diamond (BDD) electrode for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in bovine milk are presented in Analytica Chimica Acta [654 (2) 127–132 (2009)].

“Our interest was based on the high sensitivity that one can achieve with a boron-doped diamond (BDD) electrode. Since we have been working on the development of HPLC methods by direct injection of complex sample matrices, employing RAM (restrictedaccess media) columns in the first dimension of a 2D HPLC system, the use of an electrochemical detector seemed attractive,” explained main author Professor Quezia Cass from Grupo de Síntese Orgânica e CLAE at the Departamento de Química at the Universidade Federal de São Carlos.

As many drugs based on sulfonamides are often administered in the agricultural sector, they can be found in dairy products (like milk) and thus, depending on their concentration and the degree of exposure of an individual, be harmful to human health. This justified the team’s selection of sulfamethoxazole (SMX) and trimethoprim (TMP) as models compounds for a 2D HPLC method for quantification of these pharmaceuticals in bovine milk using electrochemical detection.

According to Professor Cass, the biggest problem associated with the use of an electrochemical detector is its maintenance, since it is susceptible to the accumulation of undesirable products on the electrode surface. “In order to avoid this problem, a boron-doped diamond (BDD) electrode was used as the electrochemical detector due to its unique properties, especially the absence of fouling/deactivation, as occurs with most electrode materials commonly used in electroanalytical chemistry (platinum, gold, glassy carbon, or carbon paste). Our results clearly show that the developed BDD detector presented good stability, without deactivation problems. Nevertheless, in terms of sensitivity, although satisfactory, its performance is still short of what is expected of a detector of this type,” Cass continued.

However, she added that it should be noted that the experimental chromatographic conditions were the same as those when UV detection was employed. Therefore, the team is confident that the performance of the BDD electrode can be significantly improved by changing the chromatographic conditions, especially when one considers that the electrochemical activity of this electrode for the detection of SMX and TMP is significantly higher in more acidic solutions. “At the moment we are working to achieve this goal,” she said adding that the possibility of applying the developed method for the determination of SMX and TMP in egg is also relevant, especially if one considers that the limits of detection and quantification, as obtained in this kind of analysis using a UV detector, need to be improved.

“Thus, we can establish the best chromatographic conditions for an innovative new system for the electrochemical detection of SMX and TMP not only in milk, but also in other more complex matrices such as egg or meat. Furthermore, we have been working with a series of different pharmaceuticals as food contaminants or water pollutants; thus, to have a simple and sensitive detector is very important for our research group,” she concluded.

For more information, contact the author quezia@pesquisador.cnpq.br