High-throughput and green optical sensing of thiocyanate in human saliva based on microplates and an overhead book scanner as detector.

An instrumental-free, high-throughput assay has been developed for the quantification of thiocyanate in human saliva. The proposed green method is based on the rapid reaction of the analyte with Fe(III) under acidic pH in a microplates format to form a colored complex that is captured as an image by an overhead book scanner. Optimization included the effects of the amount concentration of Fe(III), acidity and reaction time / complex stability using a total volume of 300 μL per well. Validation towards the matrix effect was focused on the specific application and was performed using both artificial and human saliva. The linearity of the developed assay was up to 500 μM thiocyanate offering a lower limit of quantification (LLOQ) of 30 μM. The green potentials were evaluated by both the Green Analytical Procedure (GAPI) and Blue Applicability Grade (BAGI) indexes. The thiocyanate content in the saliva of non-smoking volunteers ranged between 750 and 1350 μΜ, while elevated concentrations were verified in smoking individuals (1860-3080 μΜ). Statistical agreement with a corroborative method was assessed using the Bland-Altman plot.