Nanostructured cobalt(II) phthalocyanine modified screen-printed electrodes for the determination of thiocyanate in human saliva

Salivary thiocyanate is a biomarker of individual health that notably allows for the discrimination between smokers and non-smokers. Recent studies have also demonstrated its potential as a biomarker of cystic fibrosis, thus rendering the development of methods for its determination in saliva of immense importance. In response, we report on the development of graphite screen-printed electrodes (SPE) modified with cobalt(II) phthalocyanine nanosticks (CoPcNst), as low-cost and semi-disposable sensors for the determination of thiocyanate ion (SCN⁻) in human saliva. CoPCNst were synthesized and characterized using scanning electron microscopy, x-ray diffraction, as well as infrared and Raman spectroscopies. The results revealed a structural proximity to the recently identified J-polymorph. Compared with the electrode modified with commercial, beta-structure cobalt(II) phthalocyanine, the CoPc Nst/SPE provided four times better LOD and LOQ (0.49 and 1.62 μM) for thiocyanate determination by differential pulse voltammetry. The response was linear up to 20 μM SCN− (R2=0.996) and it was not affected by excess of common electro active compounds, such as ascorbic and uric acid. The analytical utility of CoPc Nst/SPE in human saliva is demonstrated.