Spectrophotometric Determination of Aqueous Sulfide on a Pneumatically Enhanced Centrifugal Microfluidic Platform

A pneumatically enhanced centrifugal microfluidic platform was developed for rapid spectrophotometric determination of aqueous sulfide. This platform performs an automated analysis based on the reaction between hydrogen sulfide and N,N-dimethyl-p-phenylenediamine in the presence of iron(III) chloride to form Methylene Blue. The platform design minimizes the number of integrated valves required, compared to other centrifugal systems, significantly improving the ease of fabrication. The sequential analytical procedure and spectrophotometric analyses were performed directly on-disk, demonstrating significant advantages in portability and cost over conventional analytical methods. This method allows for rapid and precise determination of aqueous sulfide in the concentration range of 0.4-2.0 mg L-1, which can be extended by a pneumatically induced, on-disk serial dilution to 6.0 mg L-1. A detection limit of 0.4 mg L-1 was calculated for this pneumatically enhanced method.