Trace determination of rhodamine B and rhodamine 6G dyes in aqueous samples by solid-phase extraction and high-performance liquid chromatography coupled with fluorescence detection

A simple and reliable method was developed to detect two basic synthetic dyes, rhodamine B (RB) and rhodamine 6G (R6G), in wastewater and surface water samples by high performance liquid chromatography with fluorescence detection (HPLC-FLD). These dyes have been reported to be both mutagenic and carcinogenic in various organisms. The contents of these two dyes in water samples were extracted by Oasis HLB solid-phase extraction (HLB-SPE), and were then determined by an isocratic HPLC using an Atlantis® T3-C18 column. Water samples at various pH conditions and the compositions of eluents for SPE were evaluated. The results indicate that the proposed method is precise and sensitive in analyzing these two basic synthetic dyes, and the limits of quantitation were 1.5 ng/L for RB and 0.3 ng/L for R6G in 100 mL of water samples. The recovery of analytes in spiked surface water and municipal wastewater treatment plant (WWTP) effluent samples ranged from 61 to 90% with the precision (RSD) ranging from 2 to 12%. The concentrations of analytes were detected in various water samples ranging from 0.7 to 81 ng/L.