Voltammetric behavior of chlorophyll a at a screen-printed carbon electrode and its potential role as a biomarker for monitoring fecal contamination

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 muM. 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 mug 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.