[Determination of trace azo dyes in textile wastewater by liquid-liquid extraction and dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry].

An efficient method based on liquid-liquid extraction and dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry was developed for the determination of trace azo dyes in textile wastewater. The azo dyes were reduced to aromatic amines by sodium dithionite under alkaline conditions. The main pretreatment conditions that affected the extraction efficiency were optimized. Under the optimized experimental conditions, the linear ranges of this method were as follows:0.05-10 μg/L for 13 aromatic amines; 0.05-5 μg/L for 7 aromatic amines; and 20-100 μg/L for 2,4-diaminoanisole. The correlation coefficients were in the range of 0.996-0.999. The limits of detection reached 0.05 μg/L for all the 20 aromatic amines, and the detection limit of 2,4-diaminoanisole was 20 μg/L. Actual wastewater-spiked experiments involving printing, dyeing, and weaving showed that the average recoveries of the amines were in the range of 75.6%-115.1%. The developed method has high enrichment multiples and low detection limits, and it is suitable for the detection of trace levels of banned azo dyes in textile wastewater.