Identification and quantification of CI Reactive Blue 19 dye degradation product in soil

Abstract Landfills are becoming the most common way to dispose textiles. The presence of different types of dyes and finishes on textiles fabrics can become an important source of pollution during the degradation process, due to the fact that these chemicals can leach to the soil. The biodegradation of dyes from dyed fabrics is not fully understood, and what can leach into the soil can be more toxic. In this study, cotton fabrics were dyed with CI Reactive Blue 19 (RB19) and biodegraded in soil in a laboratory‐controlled environment for a 90‐day time interval by using the ASTM D 5988‐18 method. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction method, in combination with liquid chromatography‐mass spectrometry (LC‐MS) analysis, was applied to soil containing RB19 after the degradation process. An unknown degradation product, with a mass‐to‐charge ratio (m/z) of 393, found in the soil was characterised and confirmed, via high‐resolution MS and tandem MS, to be CI Acid Blue 25 (AB25). To quantify the confirmed unknown product extracted from the degraded soil sample, a quantitation method was developed using high‐performance liquid chromatography‐diode array detector‐mass spectrometry (HPLC‐DAD‐MS). The quantitation method provided excellent linearity (R² = 0.9990 ± 0.0006), accuracy (mean percentage error = 5.17 ± 1.88), precision (mean percentage coefficient of variation = 4.73 ± 4.16), and sensitivity (lower limit of quantitation = 1.29 ± 0.47 µg/mL) for nine concentrations ranging from 0.5 to 40 µg/mL.