Voltammetric Behavior of Chlorophyll a at a Screen‐Printed Carbon Electrode and Its Potential Role as a Biomarker for Monitoring Fecal Contamination

Abstract

Direct cyclic voltammetric determination of Chlorophyll a (Chl a) at a screen‐printed carbon electrode (SPCE) resulted in a single, irreversible anodic oxidation peak at E _p = +400 mV vs. Ag/AgCl. Electrochemical investigations revealed that Chl a was adsorbing onto the SPCE surface. This adsorption phenomenon allowed the development of a method for Chl a determination, based on medium exchange followed by adsorptive stripping voltammetry (AdSV). The final protocol was optimised with respect to pH of accumulation/measurement buffer, accumulation time, and acetone content of accumulation buffer. Using this protocol, it was possible to determine Chl a in aqueous phosphate buffer over the concentration range 0.014–2.24 µM. This optimised protocol was applied to the determination of Chl a in faeces from dairy cows. The endogenous content of Chl a was calculated to be 15 mg g⁻¹ of dried faecal matter. The mean recovery for the method was 104%, with an overall coefficient of variation of 18.4%. Based on these data, the detection limit for dried faecal matter was 300 µg in 10 mL of simulated teat wash water. This approach demonstrates that the electrochemical detection of Chl a is a potential means of monitoring faecal contamination in the dairy industry.

Keywords:

• Chlorophyll a
• Screen‐printed carbon electrode
• Photosynthetic pigment
• Voltammetric study

Acknowledgments

The authors are grateful to the Commission of the European Communities for funding this work which forms part of a project designated ROSEPROMILK; contract number QLK‐CT‐2001‐01617. They also wish to thank Mr Robin Pittson and colleagues at Gwent Electronic Materials, Gwent, Wales for providing the SPCEs.