A Cost-effective Liquid Core Waveguide Based on a Concentrated Acid Medium for Colorimetric Determination of Sulfide.

A cost-effective long-path absorption liquid core waveguide (LCW) device was fabricated from a typical Teflon tube, and using a high refractive index (RI) medium of acid. It was incorporated in a flow injection-gas diffusion system for the sensitive determination of sulfide via methylene blue (MB) chemistry. The gas diffusion unit could prevent some interferences in samples. The limit of detection of 0.13 μmol L-1 was achieved without using a preconcentration procedure. The proposed device was successfully applied for sulfide determination in canal water samples with 88.7 - 103% recovery.