Munyao Joshua Sila

Munyao Joshua Sila
Project Title
Development of a Novel Voltammetric Method for Determination of Phenoxymethylpenicillin and Benzylpenicillin in Animal products and Pharmaceutical Samples
Degree Name
Doctor of Philosophy Degree in Chemistry
Project Summary


Penicillin residues in animal food products like milk and meat has attracted great concern by health

regulatory agencies due to their negative effects. Therefore, there is urgent need for reliable, low cost,

fast and simple analytical tools/methods to monitor these penicillin residues in animal products before

distribution to consumers. In our previous work, we developed a square wave voltammetric method

based on bare glassy carbon electrode in SDS/ABS media to determine penicillin V and G. In this work,

we apply this voltammetric method to detect penicillin G at trace levels in cow milk and selected

pharmaceutical samples. Using cyclic voltammetry, the electrochemical behavior of penicillin G in both

cow milk and pharmaceutical samples were obtained. The oxidation potentials were 1.65V in both

samples, same as that obtained in SDS/ABS media. The diffusion coefficients were 1.494x10-6cm2/sec

in cow milk, 2.358x10-7cm2/sec in pharmaceutical sample and 1.392x10-6cm2/sec in SDS/ABS media.

The precision for the detection of the drug was also determined and recorded as relative standard

deviation (RSD). The RSD found were 4.22% and 5.51% for cow milk and pharmaceutical sample

respectively. The percent recoveries for accuracy determination were found to lie between 95.8% -

103.0% for the cow milk and 92.0% - 96.0% for the pharmaceutical samples. These recovery percentages

were within the recommended 90.0% - 110.0%. A detection limit of 2.5×103 ng/L penicillin G was

achieved in cow milk samples against a maximum residue limit of 4.0×103ng/L set by the European

Union. Overly, this method provides simple, precise and consistent results for detection and

quantification of penicillin G in cow milk, pharmaceuticals and possibly other environmental and clinical