Bismuth film microelectrode for direct voltammetric measurement of trace cobalt and nickel in some simulated and real body fluid samples

The bismuth film microelectrode (BiFME), consisting of a bismuth film ex situ preplated onto a single carbon fibre substrate microelectrode, is presented for the direct simultaneous determination of trace Co(II) and Ni(II) in selected low-volume simulated and real human body fluid samples, using the adsorptive cathodic stripping voltammetric (AdCSV) protocol with dimethylglyoxime (DMG) as complexing agent. The BiFME exhibited well-defined and undistorted current signals for the Co(II) and Ni(II) ions, with the signals for each metal being independent of each other. Factors influencing the stripping performance at BiFME, including complexing agent concentration, accumulation potential and time, were examined. The stripping performance of the BiFME for simultaneous measurement of Co(II) and Ni(II), in the presence of dissolved oxygen, is characterised by very low detection limits of 69 ng/L (1.2 × 10−9 M) for Co(II) and 56 ng/L (9.5 × 10−10 M) for Ni(II) employing a preconcentration time of only 60 s, good linearity (r > 0.995), and excellent reproducibility with relative standard deviations of 4.6% and 3.8% for 0.5 μg/L (n = 10) of Co(II) and Ni(II), respectively. The applicability of the BiFME in direct measurement of trace Co(II) and Ni(II) in some simulated (saliva, sweat) and real (aqueous humor, cerebrospinal fluid) unpretreated low-volume (100–225 μL) biological fluids is demonstrated. The attractive behaviour of the new “mercury-free” BiFME microsensor augurs well for its use in the monitoring of Co(II) and Ni(II) release from customarily employed biomedical devices and routinely encountered metallic items, and for its deployment in clinical testing of biological fluids for cobalt and nickel exposure from medical implants.